Robbins- Chapter-14-Red-Blood-Cells.pdf

Robbins Chapter 14: Red Blood Cells
Monday, February 19, 2018
12:58 PM
 Anemia
 Reduction of the total circulating red cell mass below normal limits
 Decreased O2 carrying capacity = tissue hypoxia
 patients are pale, weak, and easily fatigued with malaise
 Mild dyspnea on exertion
 Fatty change in the liver, myocardium, kidney
 Diagnosed via hematocrit or hemoglobin
 Etiology may be determined by RBC morphology (size, shape, hemoglobinization)
 Microcytic, normochromic: disorder of hemoglobin synthesis, mostly due to iron deficiency
 Macrocytic anemia: generally impaired maturation of RBC precursors in the bone marrow
 Normocytic, normochromic: lots of diverse things
 Hematocrit
 Ratio of packed RBCs to total blood volume (the concentration)
 Not good for acute blood loss
 Volume percentage of red blood cells in blood
 Approximately 3x the [hemoglobin]
 Useful RBC Indices
 Mean cell volume (MCV): the average volume of a red cell expressed in femtoliters (fL)
 Normal: 80-100
 Mean cell hemoglobin: the average content (mass) of hemoglobin per red cell expressed in
picograms
 Changes the color of RBCs
 Mean cell [hemoglobin]: the average concentration of hemoglobin in a given volume of
packed red cells expressed in grams per deciliter
 Changes the color of RBCs
 Red Cell Distribution Width (RDW): the coefficient of variation of red cell volume
 an elevated RDW implies that the marrow is pumping out reticulocytes (larger cells)
 elevated RDW is a reactive phenomenon observed in states of anemia with a
functioning marrow
 Acute Blood Loss
 Effects are due to loss of intravascular volume
 If massive → cardiovascular collapse, shock, and death
 Normocytic-normochromic -- because it is a loss of normal blood
 Clinically depends on rate of hemorrhage, and whether bleeding is internal or external
 Survival: rapid shift of water from interstitial fluid compartment to restore blood volume
 Hemodilution = Decreased hematocrit
 Low oxygenation = EPO release from kidneys
 EPO (erythropoietin)
 Stimulates proliferation of committed erythroid progenitors (CFUE) in the marrow

 Released from the kidney
 CFUE progeny mature and are seen as reticulocytes in five days in peripheral blood
 Reticulocytosis within 7 days (10-15% reticulocytes) if severe enough
 Reticulocytes appear larger and with a blue-red polychromatophilic cytoplasm
 Thrombocytosis and leukocytosis may also occur
 Chronic Blood Loss
 Anemia only occurs if the rate of loss exceeds the marrow regenerative capacity or when iron
reserves are depleted
 Male and postmenopausal women: assume colon cancer until proven otherwise
 Hemolytic Anemias
 Definition
 Red cell life span < 120 days
 Elevated EPO levels
 Accumulation of hemoglobin degradation products (i.e. unconjugated bilirubin that’s
related to amount of liver function)
 Morphology
 Increased erythroid precursors (normoblasts) in the marrow due to increased EPO
production
 Prominent reticulocytosis in peripheral blood
 Hemosiderosis: accumulation of hemosiderin (iron containing pigment) from RBC
phagocytosis
 Extramedullary hematopoiesis if severe
 Chronically may lead to elevated bilirubin in the bile → pigment gallstones
(cholelithiasis)
 Extravascular Hemolysis
 Definition
 Occurs mostly in the macrophages of the spleen
 Predisposed by RBC membrane injury, reduced deformability or opsonization
 Clinically
 Anemia, splenomegaly (mostly extravascular) and jaundice
 Variable decreased in haptoglobin (the protein that binds to hemoglobin in plasma)
 Splenectomy is often beneficial for these patients -- a lot of the RBC destruction
happens in the spleen
 Intravascular Hemolysis
 Definition
 RBC rupture due to mechanical injury (mechanical cardiac valves), complement fixation
(mismatched blood transfusion), intracellular parasites (malaria) or extracellular toxins
(clostridial enzymes)
 Clinically
 Anemia, hemoglobinemia, hemoglobinuria, hemosiderinuria, jaundice
 No splenomegaly
 Markedly reduced serum haptoglobin
 haptoglobin: α2-globulin that binds free hemoglobin and prevents its excretion in
the urine

 is "consumed" when there is any form of hemolysis occurring
 Renal hemosiderosis (iron accumulation in the tubular cells)
 Excess unconjugated bilirubin
 Free hemoglobin may be oxidized to methemoglobin (brown color that can go into the
urine) when haptoglobin is depleted
 Hereditary Spherocytosis (HS)
 Definition
 Inherited disorder due to intrinsic defects of the red cell membrane skeleton
 RBCs become spheroid, less deformable, and more vulnerable to splenic
sequestration and destruction
 Predominantly extravascular hemolysis
 Most prevalent in Northern Europe
 Inheritance pattern
 75% are autosomal dominant
 More severe in patients who are compound heterozygotes that have two separate
mutations
 Pathogenesis
 Decreased density (insufficiency) of membrane skeletal components due to mutation in
ankyrin, band 3, spectrin, or band 4.2
 ankyrin and band 4.2 binds spectrin to the transmembrane ion transporter band
3
 protein 4.1 binds the "tail" of spectrin to another transmembrane protein,
glycophorin A
 Reduced stability of the lipid bilayer and loss of membrane fragments occurs as RBCs
age
 RBC assumes spheroidal shape, is trapped in the cords of Billroth and destroyed by
splenic macrophages after about 10-20 days instead of the normal 120 days
 RBC loss of K+
and H2O also occurs and may be due to low RBC glucose or altered pH
 Morphology
 Spherocytosis is distinctive but not pathognomonic
 small, dark-staining (hyperchromic) red cells lacking the central zone of pallor
 Reticulocytosis, marrow erythroid hyperplasia, hemosiderosis
 Moderate splenomegaly (very characteristic and consistent) due to congestion of cords
of Billroth and increased number of macrophages
 Cholelithiasis in 40-50% of patients due to pigment stones
 diagnosis
 Family history, hematology findings & lab evidence
 Osmotic fragility/lysis test in hypotonic solution
 Lab findings
 Increased RDW and MCHC
 Clinical
 patients present with variable anemia, splenomegaly and jaundice
 If severe, like in compound heterozygotes, can present at birth and require exchange
transfusion
 Increased risk of aplastic crisis due to parvovirus B19 infection since it stops
hematopoiesis for a couple of weeks
 RBC counts drop to dangerous levels

 Hemolytic crises due to infectious mononucleosis (#1 cause is EBV; #2 is CMV) may also
occur
 No splenomegaly
 Many patients will develop gall stones (pigment)
 Treatment:
 Splenectomy
 after splenectomy, the spherocytes persist but the anemia is corrected
 Increased risk of sepsis
 Anemia resolves but Howell-jolly bodies (residual RNA) remain (in all asplenic patients)
 G6PD (glucose6 phosphate dehydrogenase)
 Enzyme in the hexose monophosphate shunt
 Normally reduces NADP → NADPH
 NADPH normally reduces RBC glutathione and protects against oxidative stress
 Oxidative stress may be due to:
 Fava beans, antimalarial drugs (Quinidine, primaquine, and chloroquine),
sulfonamides, nitrofurantoins, infection, inflammation
 Resistance to Plasmodium falciparum (malaria)
 G6PD-
Deficiency
 X-linked recessive deficiency
 *G6PD-
(African variant) prominent in African Americans, and is less severe
 Episodic (not chronic) hemolysis due to oxidative stress
 In deficient cells, oxidative stress causes hemoglobin sulfhydryl crosslinking and protein
denaturation
 cross-linking of reactive sulfhydryl groups on globin chains become denatured and from
membrane bound precipitates called Heinz bodies (appear as dark inclusions visible with
crystal violet)
 Heinz bodies (denatured hemoglobin) can damage the membrane enough to cause
intravascular hemolysis
 As macrophage remove the Heinz bodies, they create "bite cells" or become spherocytic
 G6PD Mediterranean Variant
 Markedly decreased t1/2 of this enzyme causes significant intravascular hemolysis with
oxidative stress
 Protein misfolding = increased susceptibility to proteolytic degradation
 Prevalent in the Middle East
 Enzyme activity makes older RBCs prone to hemolysis with oxidative stress
 Self-limited because young RBC's not affected
 Hemoglobins
 HbA == α2β2
 HbA2 == α2δ2
 high HbA2 is a β-thalassemia (minor/trait)
 HbC
 HbF == α2γ2
 high HbF is a β-thalassemia (major)
 HbH == β4
 HbS == α2βS
2
 Sickle Cell trait

 Hemoglobin Barts == γ4
 Sickle Cell Trait (SA, α2βS
2)
 Hereditary hemoglobinopathy due to a point mutation provides protection v. falciparum
malaria
 Intracellular parasites consume O2 and decrease intracellular pH, which both promote sickling
and distorted cells are cleared more rapidly by phagocytes keeping parasite loads down
 Sickling impairs PfEMP-1 membrane knob formation which normally allows the parasite to
adhere to endothelial cells (cerebral malaria)
 Sickle Cell Anemia/Disease (SS, βS
2βS
2)
 Definition
 Hereditary hemoglobinopathy due to a point mutation (6th
position) (glutamate →
valine) in β-globin that promotes polymerization of deoxygenated hemoglobin, leading
to:
 Red cell distortion
 (extravascular) hemolytic anemia
 Microvascular obstruction --> most serious clinical features
 Ischemic tissue damage
 Heterozygotes only affected in settings of profound hypoxia
 Pathogenesis
 Deoxygenated hemoglobin forms RBC polymers when deoxygenated converting the
free flowing cytosol into viscous gel
 They then form long, needlelike fibers within RBCs causing a sickle shape; rate and
degree depend on:
 Interactions with other types of hemoglobin in the cell
 HbA interferes with the polymerization of the HbS
 Mean cell [Hb] (MCHC)
 decreased MCHC levels cause a milder disease, like in homo HbS patients
with α-thalassemia
 intracellular dehydration increases the MCHC and facilitates sickling
 Intracellular pH: decrease in pH increases the likelihood for sickling
 Transit time of RBCs through microvascular beds: slower time increases the
amount of deoxygenation and sickling
 Found most commonly in the spleen, bone marrow, and inflamed tissues
 HbSC Disease == 1 of each mutant gene
 Compound heterozygotes with RBCs that tend to lose salt and water (dehydration)
 [Hb] is then increased and there is a tendency for polymerization
 Glutamic acid → lysine ("lyCine")
 Crystals are seen on blood smear
 More mild than sickle cell disease
 Fetal Sickle Cell Anemia
 HbF is protective, and patients often present at 6 months when these levels decline
 treatment of sickle cell disease with hydroxyurea enhances expression of HbF
 End stage sickled RBCs
 Repeated damage leads to influx of Ca++
and efflux of K+
and H2O
 Chronically this causes RBCs to become dehydrated, dense and rigid
 These cells become end stage, non-deformable, irreversibly sickled cells that retain the
sickle shape even when fully oxygenated

 Hemolysis severity is proportional to the number of irreversibly sickled cells that are
sequestered and extravascularly hemolyzed
 Sickle Cell Stasis
 Higher than normal levels of adhesion molecules are expressed, which are upregulated
during inflammatory reactions
 increased tendency for the cells to arrest while moving through microvasculature
causing sickling and obstruction
 Vicious cycle of sickling, obstruction, hypoxia ensues
 Free hemoglobin binds to and inactivates NO leading to increased vascular tone and
enhanced platelet aggregation
 Stasis, sickling and thrombosis
 Morphology
 Peripheral blood: irreversibly sickled cells, reticulocytosis and target cells due to RBC
dehydration
 Howell-jolly bodies (residual RNA) due to asplenia
 Massive erythroid hyperplasia and extramedullary erythropoiesis
 Complications
 autosplenectomy:
 splenomegaly caused by trapping of sickled red cells in the cords and sinuses
during childhood
 chronic erythrostasis --> splenic infarction, fibrosis, and progressive shrinkage
 only a fibrous nubbin of fibrous splenic tissue remains by adolescence
 expansion of the marrow leads to bone remodeling:
 Skull: prominent cheekbones and changes in the skull that resemble a
"crewcut"
 facial bones: chipmunk facies
 Pigment gallstones and hyperbilirubinemia
 Microvascular occlusions of tissue (stroke, retinal problems, growth retardation)
 Vascular stagnation of subcutaneous tissue → leg ulcers in adults
 chronic hypoxia is responsible for a generalized impairment of growth and development
 Pain Crises/Vasoocclusive Crises -- this is the most important complication
 Episodes of hypoxic injury and infarction causing severe pain in the area
 Often no predisposing cause is identified
 infection, dehydration, and acidosis all favor sickling
 Bones, lungs, liver, brain, spleen, penis
 Bone crises are common in children (difficult to distinguish from acute osteomyelitis)
 Can manifest as dactylitis or acute chest syndrome
 Dactylitis/hand-foot syndrome
 Vasoocclusive infarcts in the bones leading to swollen hands and feet
 extremely common and often difficult to distinguish from acute osteomyelitis
 Common presenting sign in African American infants ∼ 6 months old with sickle cell
disease
 Acute Chest Syndrome
 Vasoocclusive crisis of the lungs in sickle cell patients
 Fever, cough, chest pain, pulmonary infiltrates
 Most common cause of death in adult patients with sickle cell anemia
 Often precipitated by pneumonia

 Causes vasodilation, slowing blood flow which increases dehydration, acidemia and
deoxygenation creating a vicious cycle
 May require transfusion or prove fatal
 Priapism
 Occurs in 45% of males after puberty and may lead to hypoxic damage and erectile
dysfunction
 Sickle Cell Anemia: Sequestration Crises
 Children with intact spleens have massive entrapment of sickle RBCs → rapid splenic
enlargement, hypovolemia and possible shock
 May require transfusion or prove fatal
 Aplastic Crises
 Parvovirus B19 infection of red cell progenitors causes a transient cessation of
erythropoiesis and sudden worsening of anemia
 Can occur in patients with sickle cell anemia
 Hyposthenuria
 Hypertonicity of the renal medulla can cause damage leading to the inability to
concentrate urine
 This increases the risk of dehydration and its attendant risk
 Infections
 Increased risk of infection due to encapsulated pathogens: Strep pneumo, haemophilus
influenzae
 Increased risk of S. Typhi osteomyelitis, S. Pneumoniae and H. Influenzae
 Haemophilus influenzae
 Most common cause of death in children with sickle cell anemia
 Can cause septicemia and meningitis
 Vaccinate children to reduce this risk
 Prophylactic antibiotics may be necessary
 Diagnosis
 Based on clinical signs and symptoms and laboratory testing of hemoglobin
 Metabisulfite screen is (+) in both disease and trait
 Electrophoresis
 Prenatal amniocentesis or chorionic biopsy
 Prognosis
 90% survive to age 20, 50% survive to 50+
 Treatment
 Hydroxyurea (DNA synthesis inhibitor) increased HbF and has an anti-inflammatory
effect
 HSC transplant is possible
 Thalassemia
 Heterogenous group of disorders due to inherited mutations that decrease synthesis of either
the α-globin or β-globin chains that compose adult HbA (α2β2)
 2 α-globin genes (4 alleles) on chromosome 16
 1 β-globin gene (2 alleles) on chromosome 11
 Causes anemia, tissue hypoxia and RBC hemolysis due to the imbalance of globin chain
synthesis
 Anemia due to decreased RBC production and decreased RBC lifespan
 Heterozygotes are protected from falciparum malaria

 β-thalassemia
 Definition
 dysregulation of the synthesis of β-globin chains
 Under hemoglobinized microcytic, hypochromic RBCs with subnormal O2 transport
capacity
 RBC life span is diminished due to imbalance of α and β globin synthesis
 Reduced beta-globin chain synthesis from beta-thalassemia leads to RBC microcytosis,
hypochromia, ineffective erythropoiesis, and excessive iron absorption. There is chronic
anemia, because the major hemoglobin A1 [α2β2] is produced insufficiently. The nature
of the mutation, typically affecting RNA transcript production, determines the severity
of the disease.
 Anemia due to:
 Ineffective erythropoiesis
 Extravascular hemolysis due to sequestration
 Β0
Thalassemia
 Absent synthesis of the β-globin chain
 Most common mutation: chain terminator creating premature stop codons
 Β+
Thalassemia
 Reduced (but detectable) synthesis of the β-globin chain
 Most common mutation: splicing mutations
 Pathogenesis
 unpaired α chains precipitate within RBC precursors → insoluble inclusions
 Inclusions cause membrane damage → precursor apoptosis
 In severe disease this causes ineffective erythropoiesis
 Those not destroyed are released with inclusions and membrane damage and are
susceptible to splenic sequestration and extravascular hemolysis
 Severe cases
 Massive erythroid hyperplasia due to ineffective erythropoiesis
 Expansion causes erosion of the bony cortex impairing bone growth and creating
skeletal abnormalities
 crew cut and chipmunk facies?
 Extensive extramedullary hematopoiesis: liver, spleen, lymph nodes
 Severe cachexia as nutrients is stolen from tissues that are O2 starved for erythroid
progenitors
 Excessive absorption of dietary iron due to suppressed hepcidin and in combination
with repeat transfusions leads to iron overload (secondary hemochromatosis)
 ineffective erythropoiesis suppresses hepcidin, a critical negative regulator of iron
absorption
 increased absorption of iron from the gut with low hepcidin levels
 decreased absorption of iron from the gut with high hepcidin levels
 Hereditary hemochromatosis results from increased iron absorption with
markedly increased iron stores. The iron accumulation in tissues results in
manifestations such as hepatomegaly, skin pigmentation, diabetes mellitus, heart
disease, arthritis, and hypogonadism.
 A 46-year-old man has had worsening arthritis and swelling of his feet for the past
year. On physical examination he has rales audible in all lung fields. A chest

radiograph shows cardiomegaly and pulmonary edema. Laboratory studies show
Hgb 13.0 g/dL, Hct 39.1%, MCV 86 fL, platelet count 255,500/uL, and WBC count
5920/uL. His serum iron is 406 microgram/mL with iron binding capacity 440
microgram/mL and ferritin 830 ng/mL (storage form of iron is markedly
elevated). Which of the following is the most likely diagnosis?
 Hereditary Hemochromatosis
 Morphology
 Anisocytosis (variable RBC size)
 Poikilocytosis (variable shape)
 Hypochromic
 Target cells: hemoglobin collects in the center of the cell
 Basophilic stippling == indicator of toxic injury to RBCs
 Fragmented RBCs
 Massive erythroid hyperplasia (crewcut + chipmunk facies)
 Iron overload: hemosiderosis and 2° hemochromatosis, affecting the heart, liver and
pancreas mostly
 β-thalassemia Major -- high HbF
 Definition
 Individuals with alleles
 Β+
/ β+
 Β+
/ β°
 Β° / β°
 have a severe, transfusion dependent anemia beginning at 6-9 months of age
 Hemosiderosis may occur secondary to transfusions
 Epidemiology
 Common in Mediterranean countries, Africa, Southeast Asia
 Clinical
 major red cell hemoglobin is HbF (markedly elevated)
 HbA2 levels are sometimes high but more often are normal or low
 high HbA2 is a β-thalassemia minor/trait
 high HbF is a β-thalassemia major
 Extravascular hemolysis
 *Hepatosplenomegaly (extramedullary hematopoiesis)
 Massive erythroid hyperplasia of skull (crewcut) and face (chipmunk facies)
 Risk of aplastic crisis due to parvovirus B19
 Treatment and prognosis
 Requires chronic transfusions: survival to 3rd decade
 Predisposed to secondary hemochromatosis (cardiac problems)
 May require iron chelators (EDTA)
 May cure with HSC transplant
 Untreated = early death due to anemia
 β-thalassemia Minor/Trait
 Definition
 Individuals with alleles (heterozygous)
 Β+
/ βwild-type
 Β° / βwild-type

 Much more common
 Mild, asymptomatic, microcytic, hypochromic anemia
 Usually asymptomatic heterozygous carriers
 Clinical
 Mild anemia with hypochromic, microcytic, basophilic stippling and target cells in
peripheral blood
 Mild erythroid hyperplasia
 Can be mistaken for iron deficiency anemia in pregnancy as they were asymptomatic
before
 Diagnosis
 Increased HbA2
 Normal HbF
 high HbA2 is a β-thalassemia (minor/trait)
 high HbF is a β-thalassemia (major)
 Must confirm diagnosis to rule out iron deficient anemia
 β-thalassemia Intermedia
 Heterozygous variant of moderate severity
 May have
 Two defective β-globin genes and an α-globin gene defect which improves
erythropoiesis effectiveness and red cell survival by lessening the imbalance in α- and β-
chain synthesis
 One defective β-globin gene and extra copies of α-globin genes, worsening the
imbalance
 Not transfusion dependent
 α-thalassemia
 Definition
 Inherited gene deletion → absent or reduced synthesis of α-globin chains
 Infants: unpaired γ-globin chains form tetramers call "Hemoglobin Barts"
 Adults: unpaired β-globin chains form tetramers called "HbH"
 β and γ chains are more soluble than free α-globin chains, and form more stable
homotetramers --> hemolysis and ineffective erythropoiesis are less severe than in β-
thalassemia
 Types based on deletions
 4 alleles on chromosome 16
 1 allele deleted = asymptomatic
 2 allele deleted = mild anemia with increased RBC count
 Cis deletion *Asian
 children of affected individuals are at increased risk of clinically
significant α-thalassemia
 symptomatic α-thalassemia is fairly common
 Trans deletion *African American
 symptomatic α-thalassemia is uncommon
 3 alleles deleted = severe anemia -- HbH tetramers
 4 alleles deleted = lethal in utero (hydrops fetalis) -- "Hemoglobin Barts"
 Silent Carrier State
 Deletion of a single gene causing a barely detectable reduction in globin chain synthesis

 patients are asymptomatic with slight microcytosis
 α-thalassemia trait
 Cis deletion: Asians
 Α/α : -/-
 *offspring are at significant risk of disease
 Trans deletion: African Americans
 Α/- : α/-
 Microcytosis with minimal anemia and no abnormal physical signs and symptoms
(asymptomatic)
 α-thalassemia trait is clinically similar to β-thalassemia minor
 Hemoglobin H disease (HBH)
 Deletion of three genes
 Most common in Asian populations
 Tetramers of β-globin chains form == called HbH
 HbH has extremely increased affinity for O2 (not useful for O2 delivery to tissues)
 tissue hypoxia disproportionate to the level of Hb
 HbH is prone to oxidation --> precipitation and intracellular inclusions promoting RBC
sequestration and phagocytosis in the spleen
 Resembles β-thalassemia intermedia
 Does not require transfusions
 Hydrops Fetalis
 Deletion of all 4 genes
 tetramers of γ-globin chains form called Hemoglobin Barts in the fetus
 Greatly increased affinity for O2 = tissue hypoxia
 Fetal distress beginning 3rd trimester
 Intrauterine fetal transfusion can save infants that used to die in utero
 Severe pallor, generalized edema and massive hepatosplenomegaly -- similar to
hemolytic disease of newborn
 Lifelong dependence on transfusions (risk of iron overload)
 HSC transplant is curative
 Paroxysmal Nocturnal Hemoglobinuria (PNH)
 Definition
 Acquired mutation of phosphatidylinositol glycan complementation Group A gene
(PIGA)
 Only hemolytic anemia caused by an acquired genetic defect
 Enzyme is essential for synthesis of certain membrane associated complement
regulatory proteins
 Absent glycosylphosphatidylinositol (GPI) = cells susceptible to destruction by
complement
 Mutations
 PIGA gene is X-linked and subject to lionization
 A single acquired mutation --> deficiency in production of GPI which attaches
important proteins to the cell membrane allowing complement dysregulation
 PNH blood cells are deficient in three GPI-linked proteins that regulate complement
activity
 CD55 (DAF) decay accelerated factor
 CD59: membrane inhibitor or reactive lysis (MIRL; most important)

 Membrane inhibitor of reactive lysis
 Potent inhibitor of C3 convertase
 Prevents spontaneous activation of the alternative complement pathway
 C8 binding protein
 Clinical
 RBCs are abnormally susceptible to lysis or injury by complement
 Intravascular hemolysis caused by the C5b-C9 membrane attack complex
 25% of cases = paroxysmal and nocturnal
 Shallow nighttime breathing = respiratory acidosis which activates complement
 Chronic hemolysis is typical = mild to moderate anemia
 Heme iron is lost in urine (hemosiderinuria) eventually leads to iron deficiency (can
exacerbate the anemia)
 Complications
 Leading cause of disease-related death: Venous thrombosis (40%) of the hepatic,
portal or cerebral veins
 5-10% develop acute myeloid leukemia (AML) or myelodysplastic syndrome
 hematopoietic stem cells have suffered some type of genetic damage
 Diagnosis
 Flow cytometry detection of RBCs deficient in GPI linked proteins (CD59)
 Treatment
 Eculizumab (prevents C5 conversion to c5a)
 Decreases hemolysis, risk of thrombosis, and required transfusions
 Increases risk of meningococcal infection
 Immunosuppression may benefit some patients with marrow aplasia
 Definitive treatment: HSC transplant
 A 42-year-old man has had multiple episodes of painful red nodules on his skin from dermal venous thrombosis, as well as
abdominal pain from mesenteric vein thrombosis over the past year. He notes passing darker urine. Laboratory studies
show Hgb 9.4 g/dL, Hct 29.2%, MCV 100 fL, platelet count 215,000/microliter, and WBC count of 8800/microliter. His
RBCs show increased sensitivity to complement lysis. Flow cytometry is most likely to show reduction in which of the
following markers on his RBCs?
 (D) CORRECT. He has paroxysmal nocturnal hemoglobinuria (PNH) an acquired stem cell disorder from mutation
in the PIGA gene that renders RBCs very sensitive to complement lysis, as well as thrombosis in unusual veins.
There is also risk for leukemia. The RBC markers CD55 and CD59 are reduced with PNH.
 Immunohemolytic Anemias (IHAs) -- most physicians call these "autoimmune hemolytic anemias"
 Definition
 antibodies bind to RBCs causing their premature destruction
 Diagnosed via the presence of antibodies and/or complement on RBCs from the patient
 Direct Coombs antiglobulin test: patient's RBCs are mixed with donor serum -- this is a
screen
 agglutination means patient has RBCs coated with antibodies
 Indirect Coombs antiglobulin test: patients serum is mixed with donor RBCs
 agglutination means patient has antibodies to patient's RBCs
 Direct Coombs Antiglobulin Test
 patient's RBCs are mixed with antibodies specific for human immunoglobulin or
complement
 (+) if the patient's RBC's have immunoglobulins already attached to them, which are
then attacked by the antihuman antibodies added
 If immunoglobulin or complement is present on the RBC surface agglutination occurs
(clumping)

 Indirect Coombs Antiglobulin Test
 Commercial RBCs with defined Antigens are mixed with the patient's serum
 (+) if patient's serum has immunoglobulins against the Antigens on the
commercial/donor RBCs
 Characterizes the antigen target and temperature dependence of the responsible
antibody
 Treatment:
 Remove initiating factors, immunosuppression or splenectomy
 Warm Antibody Type of Immunohemolytic anemia
 Definition
 Most common type of immunohemolytic anemia
 50% are idiopathic (and poorly understood).
 Also caused by drugs, autoimmune disorders (especially SLE), lymphoid neoplasms
 Pathogenesis
 Usually due to IgG (or less frequently IgA) antibodies -- "warm weather is Great"
 Extravascular hemolysis
 IgG coated RBCs bind Fc receptors on phagocytes
 Partial phagocytosis occurs as RBC membrane is removed
 RBC's become spherocytes that are sequestered in the spleen = splenomegaly
 Antigenic Drugs
 Offending agent binds to RBCs after an IV infusion
 1-2 weeks after initiation of therapy, hemolysis occurs due to antibody binding to the
drug or a complex of the drug and RBC membrane
 Extravascular hemolysis within phagocytes (most common as the antibodies act as
opsonins)
 Commonly due to penicillins and cephalosporins
 Tolerance Breaking Drugs
 Offending agents induce production of antibodies against RBC Antigens
 Particularly the Rh Antigens
 10% of patients taking α-methyldopa develop auto-antibodies (direct Coombs test) and
1% have clinically significant hemolysis
 Cold Agglutinin type of immunohemolytic anemia
 Definition
 IgM antibodies bind RBCs avidly at low temperatures (0˚C to 4˚C) -- "cold weather is
MMMiserable"
 Acute: self-limited, rarely induce clinically important hemolysis
 appear transiently following infection (e.g. mycoplasma pneumonia, EBV, CMV,
influenza virus, HIV)
 Chronic: symptomatic
 Idiopathic or associated with B cell neoplasms (eg CLL)
 chronic cold agglutinin immunohemolytic anemia caused by IgM antibodies is
more difficult to treat
 Clinical
 happens in extremity vascular beds where the temperature may fall below 30°C
 can lead to obstruction → pallor, cyanosis and Raynaud's

 Minimal complement-mediated hemolysis, but opsonized cells are phagocytosed in
spleen, liver and bone marrow
 Immunohemolytic Anemias: Cold Hemolysin
 IgG auto-antibodies bind to the P group antigen on the RBC surface in cool, peripheral regions
of the body
 Causes paroxysmal cold hemoglobinuria which is rare and potentially fatal
 When RBCs circulate to warm, central regions complement mediated lysis occurs more
efficiently
 Common in children post viral infection (transient and resolves within 1 month)
 Hemolytic Anemia due to RBC Trauma
 Often due to prosthetic cardiac valves and microangiopathic disorders
 Luminal narrowing due to deposition of fibrin and platelets → shear stress that mechanically
injures passing RBCs
 red cell fragments (schistocytes) == "burr cells," "helmet cells," and "triangle cells" on blood
smear
 Microangiopathic Hemolytic Anemia
 Most commonly seen with DIC
 Also occurs in TTP and HUS, malignant HTN, SLE and disseminated cancer
 Megaloblastic Anemias
 Definition
 Impairment of DNA synthesis that leads to ineffective hematopoiesis and distinctive
morphologic changes
 Abnormally large erythroid precursors (megaloblasts) and RBCs
 Most commonly due to vitamin B12 or folic acid deficiency (coenzymes for thymidine
and methionine synthesis)
 Morphology of the peripheral blood
 Macro-ovalocytes: large, oval RBCs (very characteristic)
 appear hyperchromic due to ample hemoglobin and larger size
 MCHC is not elevated
 Anisocytosis and poikilocytosis (variable size and shape) of the RBCs
 Decreased reticulocyte count -- indicative that the marrow is not functioning well
 Severe? Nucleated RBCs
 Hyper-segmented neutrophils ( > 5 lobes)
 Morphology of the marrow
 Hypercellular marrow due to increased hematopoietic precursors that may replace fatty
marrow
 Pro-megaloblasts (most primitive cells) are large with very basophilic cytoplasm,
prominent nucleoli, and fine nuclear chromatin pattern
 Delayed nuclear maturation with normal cytoplasmic/hemoglobin maturation that
leads to nuclear to cytoplasmic asynchrony
 Giant metamyelocytes and band forms
 Large megakaryocytes with multilobate nuclei
 Pancytopenia as marrow hyperplasia occurs due to increased EPO but abnormal DNA
synthesis = precursor apoptosis in the marrow

 Pernicious Anemia
 Definition
 Autoimmune gastritis impairs the production of intrinsic factor (IF) that is required for
vitamin B12 uptake in the gut
 Median age at diagnosis: 60 years old
 Affects all populations, especially Scandinavians
 Likely a genetic problem
 Pathogenesis
 Chronic atrophic gastritis with loss of parietal cells
 Due to autoreactive T-cell response → gastric mucosal injury & auto-antibodies
 auto-antibodies do not cause pathology, but they are of diagnostic utility
 Anemia develops when the mass of intrinsic factor secreting cells falls below threshold
 Associated with other autoimmune disorders: Autoimmune thyroiditis and adrenalitis
 Inflammasome problems and altered innate immunity
 Auto-Antibodies (Putthoff didn’t really talk about these)
 Type I: Found in plasma and gastric juice
 Type II: Prevent binding of IF-B12 complex to the ileal receptor
 Type III *85-90% of patients: recognize the α and β subunits of the gastric proton pump
in the microvilli of the parietal cell
 Not specific (seen in 50% of older people)
 Vitamin B12 Deficiency:
 Morphology of the GI
 Atrophic glossitis (beefy red tongue)
 Fundic gland atrophy (loss of chief and parietal cells)
 Intestinalization as parietal cells are replaced with mucus secreting goblet cells
 Some of the cells may double their size (a kind of megaloblastic change)
 Morphology of the CNS
 CNS lesions: demyelination of dorsal and lateral spinal cord tracts
 spastic paraparesis, sensory ataxia, and severe paresthesias in the lower limbs
 Megaloblastic erythroid hyperplasia
 Giant myelocytes and metamyelocytes
 Hyper-segmented neutrophils (>5 lobes)
 Megakaryocytes with large, multilobed nuclei
 Diagnosis
 Moderate-severe megaloblastic anemia
 Leukopenia with hyper-segmented granulocytes
 Decreased serum B12
 Increased homocysteine and methylmalonic acid
 methylmalonic acid will not be increased in folate deficiency
 hematocrit should rise ∼ 5 days after administration of B12 with increased reticulocytes
-- diagnosis is confirmed following administration of "B12 challenge" and gauging
response
 serum antibodies to intrinsic factor are highly specific for pernicious anemia
 cause of pernicious anemia; not the presence/absence of vitamin B12 deficiency
 Treatment
 High dose or parenteral administration of B12 or folate

 folate can cause worsening of the mental problems without also giving B12
 Sequelae
 Atrophy and metaplasia of gastric mucosa associated with pernicious anemia -->
increased risk of gastric carcinoma (no change in risk after treatment)
 Increased homocysteine --> increased risk for atherosclerosis and thrombosis
 Neurological disease is due to accumulation of methylmalonic acid in the spinal cord
 Parenteral or high dose B12 cures the anemia and will halt or reverse the
peripheral neurologic disease
 Anemia of Folate Deficiency
 deficiency of folic acid results in a megaloblastic anemia having the same pathologic features
as that caused by vitamin B12 deficiency -- folate deficiency has no neurological sequelae
 suppressed synthesis of DNA is the common denominator of folic acid and vitamin B12
deficiency and it the immediate cause of megaloblastosis
 methylmalonic acid will be within normal limits
 Porphyria
 Definition
 Set of diseases that can be acute or chronic
 Due to problems in the synthesis of heme, most are inherited, but some can also be
acquired (including the most common type that arises in the liver)
 problems in the bone marrow leads to anemia and splenomegaly
 problems in the liver leads to liver damage and an increased risk in hepatocellular
carcinoma
 Clinical
 Chronic
 Skin: very sensitive to sunlight leading to blisters and abnormal hair growth
 Teeth: staining
 Acute
 Referred pain from the thorax and abdomen
 Seizures, hallucinations, and general psychosis
 Causes of Vitamin B12 Deficiency
 Impaired absorption
 Achlorhydria (impairs B12 release from food)
 Gastrectomy causes loss of intrinsic factor
 Loss of exocrine pancreas function (impairs B12 release from haptocorrin)
 Loss of pepsin secretion
 Resection of the terminal ileum
 Malabsorption syndromes (including *fish* tapeworms Diphyllobothrium latum)
 Increased requirements (pregnancy, hyperthyroidism, disseminated cancer, chronic infection)
 Pernicious anemia (antibodies to intrinsic factor)
 FH4 Metabolic Processes
 Purine synthesis
 Conversion of homocysteine to methionine
 Deoxythymidylate monophosphate (dTMP) synthesis (for DNA synthesis)
 Reductase step (FH2 → FH4) can be inhibited by many drugs (e.g. trimethoprim)

 trimethoprim inhibits (bacterial) dihydrofolate reductase and halts DNA synthesis
 Anemia of Folate (pteroylmonoglutamic acid) Deficiency
 Definition
 Megaloblastic anemia within months due to:
 Decreased dietary intake
 Increased requirements (pregnancy, cancer, infancy)
 Impaired utilization (folate antagonists)
 Absorption of folate
 Found in green vegetables and some animal sources, but are sensitive to heat
 Absorbed in the proximal jejunum
 Commonly seen due to
 Common in chronic alcoholics, elderly and the indigent (poor) due to inadequate diet
 Alcoholism may lead to trapping in the liver, urinary loss and altered metabolism
 patients with malabsorption syndromes (celiac disease) or diffuse infiltrative disease of
the small intestine may not obtain adequate amounts
 Phenytoin and oral contraceptives can interfere with absorption
 Folic acid antagonists (methotrexate) or other chemotherapy drugs inhibit metabolism
particularly in bone marrow and the GI tract (rapidly growing cells that do a lot of DNA
synthesis)
 Anemia of Folate vs anemia due to Vitamin B12 deficiency
 Normal [methylmalonate]
 No neurological signs and symptoms
 Increased homocysteine (same as B12 anemia) but methylmalonate concentrations are
normal
 Neurological changes do not occur in folate deficiency anemia
 Diagnosed via demonstration of decreased folate levels in the serum or RBCs
 Rule out B12 deficiency before treating with folate
 folate may exacerbate neurological defects of B12 deficiency
 Treatment
 Folic acid administration
 Iron Deficiency
 Most common nutritional disorder of the world
 dietary lack
 impaired absorption
 increased requirement
 In the Western world, most commonly due to chronic blood loss
 Signs and symptoms related to inadequate hemoglobin synthesis
 Ferritin -- storage form of iron
 ubiquitous protein-iron complex found at highest levels in the liver, spleen, bone marrow, and
skeletal muscles
 located in the cytosol and lysosomes
 partially degraded protein shells of ferritin --> hemosiderin granules
 plasma ferritin derived largely from storage pool of iron; directly related to body iron levels
 hemosiderin granules
 partially degraded protein shells of ferritin
 iron in hemosiderin is chemically reactive and turns blue-black when exposed to potassium
ferrocyanide

 Prussian Blue Stain
 disappearance of stainable iron from macrophages in the bone marrow ==
diagnostically significant finding of iron deficiency
 in iron overloaded states (e.g. hemochromatosis), most iron is stored in hemosiderin
 Hepcidin
 synthesized and released from the liver in response to increases in intra-hepatic iron levels
 Regulates iron absorption in the proximal duodenum
 Inhibits iron transfer from enterocyte to plasma by binding ferroportin
 Causes endocytosis and degradation of ferroportin
 hepcidin inhibits ferroportin function in macrophages and reduces the transfer of iron from
the storage pool to developing erythroid precursors in the bone marrow
 as hepcidin levels rise, iron becomes trapped in duodenal cells that eventually slough off ==
excretion of iron
 when body is replete with iron, high hepcidin levels inhibit its absorption into the blood
 hepcidin levels directly related to total body iron stores
 Anemia of Chronic Disease/Inflammation is caused in part by inflammatory mediators that
increase hepatic hepcidin production
 TMPRSS6 mutation related anemia (didn't talk about it)
 Hepcidin is normally suppressed by TMPRSS6 protease when iron stores are low
 Dysfunctional = microcytic anemia
 because of inability to absorb iron
 No response to iron therapy
 Hepcidin and hemochromatosis
 inappropriately decreased levels in 1° and 2° hemochromatosis (systemic iron overload)
 Suppressed by ineffective erythropoiesis, even if iron stores are high (as happens in β-
thalassemia major and myelodysplastic syndromes)
 Hepcidin is structurally related to defensins (intrinsic anti-bacterial activity)
 iron sequestration may enhance body's ability to fend off certain types of infection
 Haemophilus influenzae and Yersinia enterocolitica (pseudo-appendicitis) require iron
for pathogenicity
 Iron Deficient Anemia
 Causes
 Dietary lack (infants, teens, elderly and impoverished)
 Impaired absorption (celiac disease, steatorrhea, chronic diarrhea)
 Increased requirement like in growing kids and pregnancy
 *Chronic blood loss* (external hemorrhage or bleeding into the GI or GU tracts)
 Iron deficiency in men or postmenopausal women is GI bleed until proven otherwise
(cancer or occult)
 Morphology
 Disappearance of stainable iron from macrophage in the bone marrow, assess with
Prussian blue stain
 Microcytic, hypochromic anemia in blood smears, but is normocytic, normochromic in
the beginning
 well established iron deficiency anemia is a microcytic, hypochromic anemia with
modest poikilocytosis

 Central pallor is enlarged in RBCs and hemoglobin may only be seen in a narrow
peripheral rim
 Poikilocytosis (pencil cells) is characteristic
 Mild to moderate erythroid hyperplasia
 Clinical
 Koilonychia == spoon nails
 Alopecia
 Atrophic changes in the tongue and gastric mucosa
 Intestinal malabsorption
 Pica: eat non-food items like dirt and move limbs during sleep
 pica: desire to eat non-food substances (i.e. ice, clay) to replenish depleted iron
 Plummer-Vinson Syndrome
 Microcytic, hypochromic anemia -- i.e. late iron deficient anemia
 Atrophic glossitis
 Esophageal webs
 Diagnosis
 Decreased hemoglobin and hematocrit
 Microcytic, hypochromic anemia (when well established)
 Poikilocytosis (abnormal RBC shape)
 Decreased serum iron and ferritin
 Increased iron binding capacity
 Decreased transferrin % < 15
 Inhibition of hepcidin synthesis
 Labs
 HCT and Hgb decreased
 serum iron is low
 plasma ferritin is low -- storage form of iron
 inversely related to TIBC which is high
 TIBC is inversely related iron saturation (and therefore directly related to
plasma ferritin)
 serum hepcidin is low
 hepcidin inhibits iron absorption; in IDA, trying to absorb more iron therefore
makes sense it is high
 Anemia of Chronic Disease
 Definition
 Most common cause of anemia in hospitalized patients
 Reduced proliferation of erythroid progenitors and impaired iron utilization due to:
 Chronic microbial infections (osteomyelitis, bacterial endocarditis, lung abscesses)
 Chronic immune disorders (RA, regional arteritis)
 Neoplasms (lung, breast, Hodgkin's lymphoma)
 microcytic, hypochromic anemia (may also be normocytic, normochromic)
 Pathogenesis
 occur in the setting of persistent systemic inflammation
 IL-6 stimulates an increase in the hepatic production of hepcidin
 associated with low serum iron, reduced total iron binding capacity, and abundant
stored iron in tissue macrophages
 Treatment

 Treat the underlying condition (whatever is causing the chronic inflammation
 Some patients may benefit from exogenous EPO as patients generally have a low EPO
level
 Aplastic Anemia
 Definition
 Syndrome of primary hematopoietic failure and attendant pancytopenia
 Autoimmune is the most common cause, but HSC problems can also be inherited or
acquired
 Idiopathic in 65% of cases
 Toxic exposure.
 Whole body irradiation *dose dependent (only?)*
 Drugs that cause dose related, reversible marrow suppression (chemotherapy drugs,
benzene)
 Drugs that cause unpredictable, idiosyncratic reactions that typically have little or no
marrow suppression (chloramphenicol, gold salts)
 Viral infection
 Hepatitis (non-A, non-B, non-C, and non-G type… so Hepatitis D and E)
 65% are idiopathic
 Fanconi Anemia
 Autosomal recessive disorder caused by defective protein complex necessary for DNA
repair
 Presents early in life; often accompanied by congenital anomalies
 Hypoplasia of the kidney or spleen
 Bone anomalies of the thumbs or radii
 Telomerase Mutation
 5-10% of adult onset aplastic anemia
 This enzyme is necessary for cellular immortality and limitless replication
 Deficits may lead to premature HSC exhaustion and marrow aplasia
 Short Telomeres
 Seen in ∼ 50% of patients with aplastic anemia
 May be due to an undiscovered defect or as a consequence of excessive stem cell
replication
 Pathogenesis (2 models)
 extrinsic, immune-mediated suppression of marrow progenitors
 TH1 cells are activated against these Antigens → IFNγ and TNF to suppress and kill
hematopoietic progenitors
 Upregulation of apoptotic genes
 Anti-thymocyte globulin (immunosuppressive) agents suppress autoreactive T-cell
clones producing a response in 60-70% of patients
 intrinsic abnormality of stem cells
 Stem cells are antigenically altered via exposure to drugs, infectious agents, etc
 Morphology
 Hypocellular bone marrow
 HSC replaced by fat cells, fibrous stroma, and scattered Lfs
 "Dry tap" on marrow aspiration, bone marrow biopsy necessary for diagnosis
 Granulocytopenia: mucocutaneous bacterial infection
 Thrombocytopenia: abnormal bleeding

 Systemic hemosiderosis if multiple transfusions are given
 Clinical (pancytopenia ultimately develops)
 Anemia --> Weakness, pallor, dyspnea
 Thrombocytopenia --> Petechiae and ecchymoses
 petechial bleeding is often characteristic of platelet disorders (thrombocytopenia)
 Neutropenia --> Persistent infections or sudden onset of fever and chills (rigors)
 No immune response? Fever may be absent
 Reticulocytopenia: RBCs are macrocytic, normochromic
 No splenomegaly (if present, question diagnosis)
 Causes of Pancytopenia
 Aplastic Anemia: hypocellular bone marrow
 aleukemic leukemia and myelodysplastic syndromes: hypercellular bone marrow
 Treatment
 Bone marrow transplant (5 year survival > 75%)
 Immunosuppression in older patients or those without a suitable donor
 Pure Red Cell Aplasia
 Definition
 Primary marrow disorder in which only erythroid progenitors are suppressed
 Associated with thymoma and large granular lymphocytic leukemia, drugs, autoimmune
disorders, parvovirus B19, metastatic carcinoma, spent phase MPS
 Parvovirus B19
 Transient in normal individuals as they clear the infection in 1-2 weeks
 May lead to an aplastic crisis in patients with moderate-severe hemolytic anemias due
to brief cessation of erythropoiesis
 Parvovirus B19 infects erythroid precursors and can lead to an aplastic crisis in
persons with hemoglobinopathies. The hemoglobinopathy impairs the marrow
ability to respond to the stress of the acute infection.
 patients who are chronically immunosuppressed (HIV) means the infection can persist
due to ineffective immune response
 Treatment
 Thymoma resection = 50% of patients have hematologic improvement
 No thymoma? Treatment with immunosuppression
 Myelophthisic Anemia
 Marrow failure where space occupying lesions replace normal marrow elements leading to:
 Destruction or distortion of marrow architecture
 Leukoerythroblastosis: abnormal release of nucleated erythroid precursors and
immature granulocytic forms into peripheral smears; even more immature than bands
 Teardrop RBCs: deformed during their tortuous escape from the fibrotic marrow
 Depressed hematopoiesis
 Pancytopenia
 most common cause == metastatic cancer from the breast, lung, or prostate
 also a feature of the spent phase of myeloproliferative disorders
 Myelophthisic Disease
 Metastatic tumor involving marrow, or marrow fibrosis, is a 'myelophthisic' process that
reduces normal hematopoiesis and leads to a peripheral 'leukoerythroblastic' picture
with immature RBC's and WBC's in the peripheral blood, as seen here with nucleated

RBCs and white cells even more immature than bands (metamyelocytes, myelocytes) on
the smear.
 Chronic Renal Failure leading to anemia
 Definition
 Associated with an anemia proportional to the severity of the uremia
 Kidneys produce less EPO causing inadequate RBC production
 There can also be an extra-corpuscular defect that shortens the lifespan of the RBCs
and platelet dysfunction with increased bleeding
 Treatment
 Recombinant EPO
 +/ iron replacement therapy
 Hepatocellular Liver Disease
 Decreased marrow function due to
 Toxins, infections, cirrhosis
 Can be exacerbated by vitamin B12 or folate deficiencies as well as excessive bleeding
(varices)
 Predominantly erythroid progenitor suppression
 Slightly macrocytic anemia due to lipid abnormalities with RBC membranes acquiring
phospholipid and cholesterol as they circulate
 Polycythemia
 Abnormally high red cell count, usually with an associated increase in the hemoglobin level
 Relative or absolute
 Relative Polycythemia
 Hemoconcentration due to decreased plasma volume, commonly a result of dehydration
 Water deprivation
 Prolonged vomiting or diarrhea
 Excessive diuretic use
 Gaisbock syndrome (stress polycythemia): HTN, obese, anxious patients
 Absolute Polycythemia
 Increase in the total red cell mass
 Primary (Polycythemia vera)
 Intrinsic abnormality of hematopoietic precursors
 this is a myeloproliferative disorder
 Secondary
 Red cell precursors are responding to increased levels of EPO
 i.e. physiologic response at high altitudes or pathophysiologic, EPO producing tumors or
HIF1α stabilization
 Renal cell carcinomas are known to secrete erythropoietin and lead to this
paraneoplastic effect with polycythemia
 Polycythemia Vera
 Most common cause of primary polycythemia
 Myeloproliferative disorder associated with mutations leading to EPO-independent growth
of red cell progenitors
 Familial EPO receptor mutations can also induce EPO-independent receptor activation
 HIF-1α == hypoxia-induced factor; stimulates the transcription of the erythropoietin gene

BLEEDING DISORDERS: HEMORRHAGIC
DIATHESES____________
 Excessive Bleeding
 May be due to:
 Increased fragility of vessels
 Platelet deficiency or dysfunction
 Derangement of coagulation
 Prothrombin Time (PT) -- "Play Tennis OUTside"
 Assesses the extrinsic (primary pathway in vivo) and common coagulation pathways
 Clotting of plasma after adding exogenous tissue thromboplastin and Ca++
 Prolonged due to deficiency or dysfunction of Factor V, VII, X, prothrombin or fibrinogen
 Factor VII is different
 Measured in patients taking coumadin (warfarin)
 Partial Thromboplastin Time (PTT) -- "Play Table Tennis INside"
 Assesses the intrinsic and common coagulation pathways
 Clotting of plasma after adding kaolin, cephalin and Ca++
ions
 Prolonged due to deficiency or dysfunction of factors V, VIII, IX, X, XI, XII, prothrombin or
fibrinogen (or interfering antibodies to phospholipid)
 Factor VIII, IX, XI, and XII are different
 do this one if you suspect hemophilia
 Measured in patients taking heparin
 Platelet Count
 An electronic particle counter determines this value on anticoagulated blood
 If abnormally low: do a peripheral blood smear and observe for clumping of platelets
 During automated counting this can cause a "thrombocytopenia"
 High counts may indicate myeloproliferative disease (essential thrombocythemia)
 Bleeding Disorder: Vessel Wall Abnormalities
 Definition
 Relatively common, lead to petechiae and purpura without serious bleeding
 Can sometimes bleed into more serious places
 Labs
 Platelet counts are normal
 PT, PTT and bleeding times are normal
 Infection
 Microbial damage to microvasculature (vasculitis) and DIC
 Often due to meningococcemia which, if not recognized, can be catastrophic
 Also caused by septicemia, infective endocarditis, rickettsioses, Neisseria infection
 Drug Reaction
 Cutaneous petechiae and purpura may be seen without thrombocytopenia
 Due to immune complex deposition with resulting hypersensitivity (leukocytoclastic)
vasculitis
 Scurvy, Ehlers-Danlos Syndrome -- Putthoff: "not common at all… never see it"

 Poor vascular support leads to microvascular bleeding from collagen defects
 Also seen in patients with Cushing syndrome where peri-vascualr supporting tissue is
lost due to excess corticosteroid production → spontaneous purpura (usually older
adults)
 Henoch-Schonlein Purpura
 Systemic hypersensitivity due to immune complex deposition (IgA most commonly),
particularly in the glomerular mesangial region
 Purpuric rash, colicky abdominal pain, polyarthralgia, and acute glomerulonephritis
 Hereditary Hemorrhagic Telangiectasia (Weber-
Osler-Rendu Syndrome)
 Autosomal dominant disorder of TGFβ signaling dysregulation
 patients have dilated, tortuous, thin-walled vessels
 bleeding can occur anywhere, but is most commonly under the mucous membranes of
the nose (epistaxis), tongue, mouth, eyes and throughout the GI tract
 serious bleeding may occur
 Thinning of vessel walls with telangiectatic formations, AV malformations, aneurysmal
dilations throughout body
 Vermillion border of the lip and on the tongue
 Autosomal dominant inheritance (chromosome 9)
 Endoglin (CD105) gene
 Most frequent symptom/presentation: recurrent epistaxis
 Telangiectasias and other bleeding
 Treatment: mostly benign and exsanguination is rare
 Surgery or photoablation in select patients
 Perivascular Amyloidosis
 Amyloid light chain amyloidosis manifests as mucocutaneous petechiae from weakened
blood vessel walls
 will see this in multiple myeloma???
 Thrombocytopenia
 Definition
 Reduced platelet number < 100,000
 Platelet Counts
 <10,000 == indication for platelet transfusion
 < 20,000: Spontaneous (non-traumatic) bleeding
 20,000-50,000: Exacerbates posttraumatic hemorrhage
 Most spontaneous bleeds involve small vessels of the skin and mucous membranes
 Most feared: intracranial bleeding
 PT and PTT will be normal
 Decreased Production
 Marrow output is suppressed generally as in aplastic anemia or leukemia
 Megakaryocytes are selectively suppressed as with specific drugs or alcohol taken in
excess
 May also occur in isolation in patients with HIV (can infect megakaryocytes) or
myelodysplastic syndromes

 Decreased Platelet Survival
 Increased consumption or activation of platelets
 Mechanical injury
 DIC, thrombotic microangiopathies (TTP, HUS)
 TTP (thrombotic thrombocytopenic purpura)
 HUS (hemolytic uremic syndrome)
 Immune mediated destruction of platelets: ITP
 Autoimmune thrombocytopenia: allo-antibodies: transfusion or IgG crossing the
placenta
 Sequestration
 Dilution
 There is a relative reduction in the number of circulating platelets (viable platelet
numbers are decreased) with prolonged storage of blood for transfusion
 Chronic Immune Thrombocytopenic Purpura (ITP)
 Definition
 Primary or secondary auto-antibodies (IgG) destruction of platelets
 Secondary association with SLE, HIV and B-cell neoplasms (CLL)
 Most commonly found in women <40 years old, 3X more likely in females
 Pathogenesis
 primary pathogenesis == auto-antibodies against platelets
 IgG antibodies that opsonize platelets; platelets are then removed by the spleen
 NO ATTENDANT SPLENOMEGALY THOUGH
 IgG antiplatelet antibodies directed against membrane glycoproteins
 IIb/IIIa -- Glanzmann Thrombocytopenia
 Ib/IX -- Bernard-Soulier Syndrome
 Opsonized platelets are destroyed by phagocytes expressing IgG Fc receptors
 Splenectomy removes the source of the some of the auto-antibodies and the site of
platelet destruction
 Morphology
 Spleen, bone marrow and blood are affected, but changes are not specific
 Normal sized spleen with sinusoidal congestion and prominent germinal centers, there
may be megakaryocytes in the spleen
 Modestly increased number of bone marrow megakaryocytes
 Abnormally large platelets may be seen on peripheral blood smear
(megathrombocytes)
 Clinical
 Insidious onset characterized by bleeding into the skin and mucosal surfaces
 initially as pinpoint hemorrhages (petechiae) that may become confluent (now
called ecchymoses)
 most prominent in the dependent areas where the capillary pressure is higher
 Epistaxis, easy bruising, gum bleeding from minor to no trauma
 Patient may present with melena, hematuria, or excessive menstrual flow
(menorrhagia)
 Treated patients rarely develop subarachnoid or intracerebral hemorrhage
 No splenomegaly or lymphadenopathy (consider secondary causes ie B cell neoplasm)
 Labs

 Normal PT and PTT
 Low platelet count (those seen on peripheral blood smear are large)
 Normal or increased megakaryocytes
 Diagnosis
 Diagnosis of exclusion (no reliable antibody tests)
 Treatment:
 almost all patients will respond to glucocorticoids (inhibit phagocyte function) but many
will relapse
 Splenectomy normalizes patient's platelet count
 also increases risk for bacterial sepsis (weigh pros and cons)
 IVIG or rituximab (anti-CD20 antibody) in patients who relapse after splenectomy or
when splenectomy is contraindicated
 Thrombopoietin (TPO) mimetics may also stimulate platelet production
 Acute Immune Thrombocytopenic Purpura (ITP)
 Disease of childhood which appears abruptly 1-2 weeks after self-limited viral infection --
chronic form == adults
 effects both sexes equally (no gender preference)
 Auto-antibodies to platelets develop via an unknown mechanism -- same as in chronic form
 Self-limited with resolution in six months
 severe cases of thrombocytopenia can be treatment with glucocorticoids
 20% of patients (usually without viral prodrome) disease persists in a chronic form,
resembling the adult disease (worse outcome)
 Drug Induced Thrombocytopenia
 Drugs such as quinine, quinidine (malaria drugs), and vancomycin that bind platelet
glycoproteins and create antigenic determinants that are recognized by antibodies (i.e. act as
haptens or participate in the formation of immune complexes that deposit on platelet
surfaces)
 antibodies to the drug or the modified platelet molecules leads to macrophage ingestion and
platelet removal
 True auto-antibodies may be induced by agents
 Platelet inhibitory agents that bind glycoprotein IIb/IIIa can also lead to the creation of an
immunogenic epitope
 Heparin Induced Thrombocytopenia (HIT):
 Type I
 Occurs rapidly after the onset of therapy
 Likely due to direct platelet aggregating effect of the drug
 Little clinical significance and can resolve despite continuing therapy
 Type II
 Life threatening venous and arterial thrombosis
 antibodies form to HEP-PF4 complexes (platelet factor 4 is a normal component of
platelet granules), activates the platelets, and promotes life-threatening thrombosis
(arterial and venous) occurs even in the setting of thrombocytopenia
 Occurs 5-14 days after therapy begins
 DVT → PE
 PE in the setting of a thrombocytopenia

 thrombocytopenia usually associated with bleeding; this is different
 Clots of large arteries → limb loss
 Therapy MUST be discontinue and another anti-clotting agent must be used
 risk of severe HIT is lowered, but not completely eliminated, by the use of low-
molecular weight heparin preparations (low molecular weight heparin cannot be
used as replacement anti-coagulant therapy should severe HIT arise)
 HIV-associated Thrombocytopenia
 thrombocytopenia is one of the most common hematologic manifestations of HIV infection
 This virus may infect megakaryocytes that express CD4 (receptor) and CXCR4 (coreceptor)
 Infected megakaryocytes are prone to apoptosis and have an impaired ability to produce
platelets
 B-cell hyperplasia and dysregulation → auto-antibodies that may be directed against platelet
membrane glycoprotein IIb/IIIa (opsonization)
 Thrombotic Microangiopathy
 intravascular thrombi cause a microangiopathic hemolytic anemia and widespread organ
dysfunction, and the attendant consumption of platelets leads to thrombocytopenia
 TTP (thrombotic thrombocytopenic purpura)
 pentad: fever, thrombocytopenia, microangiopathic hemolytic anemia, transient
neurologic deficits, and renal failure
 HUS (hemolytic uremic syndrome)
 associated with microangiopathic hemolytic anemia and thrombocytopenia but is
distinguished by the absence of neurologic symptoms, the prominence of acute renal
failure, and its frequent occurrence in kids
 PT & PTT are normal
 DIC: activation of the coagulation cascade is of primary importance and PT and PTT will
be abnormal
 Thrombotic Thrombocytopenic Purpura (TTP)
 Definition
 Hyaline thrombi occlude the capillaries of all organs in the body
 Decreased ADAMTS13 (aka "vWF metalloprotease"), either acquired or inherited
 Normally, ADAMTS13 degrades high-molecular-weight multimers of vWF
 Exacerbated by endothelial injury
 Uncleaved multimers → abnormal platelet adhesion and microthrombi
 Most common in in females
 The pentad of fever, mental changes, renal failure, thrombocytopenia,
and microangiopathic hemolytic anemia is characteristic of TTP. Platelets are activated
directly, and not the coagulation system as a whole, so that the prothrombin time,
partial thromboplastin time, and D-dimer are either not elevated or minimally elevated.
The platelet activation leads to formation of hyaline thrombi in small arteries that
promotes tissue ischemia in organs such as brain, with consequent neurologic
impairment. Platelet transfusion is contraindicated.
 Origin
 Most commonly due to acquired auto-antibodies to ADAMTS13

 Hereditary form is a mutation of the ADAMTS13 gene, often present in adolescence
with episodic signs and symptoms that needs a trigger to cause the events
 Acquired from has auto-antibodies directed against ADAMTS13
 Clinical
 TTP Pentad: Fever, Thrombocytopenia, Microangiopathic hemolytic anemia, Transient
neurological deficits, and Renal failure
 Labs
 PT and PTT are normal early in the disease
 Lab tests late in the course suggest DIC
 Treatment
 Plasma exchange/plasmapheresis
 Untreated: 100% mortality
 Hemolytic Uremic Syndrome (HUS)
 Signs & symptoms
 Fever
 Microangiopathic hemolytic anemia
 Renal failure
 *Typical* Hemolytic Uremic Syndrome (HUS)
 Occurs due to endothelial damage by drugs or infection
 Children or elderly with E. Coli O157:H7 dysentery (undercooked beef)
 E. Coli shiga-like toxin (verotoxin) damages endothelial cells causing platelet microthrombi
 patients present with bloody diarrhea and then go onto HUS a few days later
 Irreversible renal damage and death can occur in severe case.
 Treatment is supportive
 *Atypical* Hemolytic Uremic Syndrome (HUS)
 Acquired or inherited defect of complement factor H (CD46) or factor I
 Affected proteins normally prevent excess activation of the alternative complement pathway
 Immunosuppression can help patients that have auto-antibodies to the inhibitory
complement factors
 3 categories of inherited defective Platelet Dysfunction
 Defects of adhesion
 Defects of aggregation
 Disorders of platelet secretion (release reaction)
 Bernard-Soulier Syndrome == defective adhesion of platelets to subendothelial matrix (BS adhesion)
 Inherited deficiency of platelet membrane glycoprotein complex Ib-IX
 This is a receptor for vWF and essential for normal platelet adhesion to subendothelial matrix
 Patients have variable, often severe, bleeding tendency
 abnormally large platelets on a peripheral smear -- giant platelets
 absent aggregation to ristocetin
 will aggregate to ADP, collagen, epinephrine, or thrombin
 Glanzmann Thrombasthenia == defective platelet aggregation (Mann, Agg)
 Autosomal recessive deficiency or dysfunction of glycoprotein IIb/IIIa (integrin that
participates in "bridge formation" between platelets by binding fibrinogen)
 Failure of platelets to aggregate in the presence of ADP, collagen, epinephrine, or thrombin

 Bleeding tendency is often severe
 Two teenage siblings in the same family are noted to have frequent nosebleeds and easy
bruising from even minor trauma. Both have had menorrhagia since menarche. One girl's CBC
shows Hgb 14 g/dL, Hct 42.3%, MCV 90 fL, platelet count 242,000/microliter, and WBC count
7720/microliter. Her prothrombin time is 12 seconds and partial thromboplastin time 25
seconds. Platelet function studies show decreased aggregation in response to ADP, collagen,
epinephrine, and thrombin. Which of the following disorders are these siblings most likely to
have?
 Glanzmann Thrombasthenia
 will aggregate to ristocetin; will not aggregate to ADP, collagen, epinephrine, or thrombin
 normal platelets
 Aspirin and other NSAIDs on platelets
 Acquired defect in platelet aggregation
 Aspirin is a potent, irreversible inhibitor of COX which is required for synthesis of TxA2 and
PGs
 Antiplatelet actions are important for prophylaxis of coronary thrombosis
 Uremia
 Acquired defect in platelet function
 defects in adhesion, granule secretion, and aggregation
 Bleeding due to coagulation factor deficiencies often occurs into the gastrointestinal and urinary
tracts and into weight-bearing joints (hemarthrosis)
 oozes blood for days after a tooth extraction
 develops a hemarthrosis after minor stress on a knee joint -- this is suggestive of hemophilia
(A or B), not vWF
 Vitamin K Deficiency
 Definition
 Normally activated by epoxide reductase in the liver
 Deficiency leads to impaired synthesis of factors II, VII, IX, X, Protein C -- "1972" and
Protein C
 this is what Warfarin/Coumadin impairs
 Common in newborns (lack of GI colonization, bacteria produce this agent)
 Give prophylaxis at birth
 Causes
 Occurs in patients taking warfarin/coumadin
 warfarin/coumadin antidote == vitamin K
 Also due to chronic antibiotics (bumping off gut bacteria), severe liver disease
 Clinical
 Bleeding/hemorrhage
 Prolonged PT (because this is what you check with warfarin/coumadin)
 Treatment
 Replacement of deficiency (corrects PT in 12-18 hours)
 Fresh frozen plasma (liver disease or acute hemorrhage, need PT corrected ASAP)
 Clotting Factor Abnormalities

 Bleeding manifests as large ecchymoses or hematomas after injury or as prolonged bleeding
after laceration or surgery
 May bleed into GI or GU tracts, or into weight bearing joints (hemarthrosis) (unlike
thrombocytopenia)
 May be acquired or inherited
 Acquired usually means deficiency of many factors
 Hereditary typically affect a single factor
 Von Willebrand Factor (vWF)
 Produced by endothelial cells, megakaryocytes (α-granules)
 vWF Stabilizes factor VIII -- "VolksWagen Factories make gr8 diesels"
 when vWF is deficient, Factor VIII is missing and this prolongs PTT
 Promotes adhesion of platelets to the subendothelial matrix
 This occurs via glycoprotein Ib-IX
 Measured using Ristocetin agglutination test
 Factor XIII
 Made in Kupffer cells of the liver and sinusoidal endothelial cells (bone marrow, spleen,
kidney)
 Binds vWF in circulation (stabilized)
 Unbound t1/2 = 2.4 hours
 Bound t1/2 = 12 hours
 Essential cofactor for factor IX
 Measured by coagulation assays with patient plasma and factor VIII deficient plasma
 Von Willebrand Disease
 Definition
 Most common inherited bleeding disorder of humans (1% of the US adult population)
 Autosomal dominant disorder presenting with spontaneous bleeding from mucous
membranes, excess bleeding from wounds or menorrhagia (excessive menstrual
bleeding)
 Usually mild and unnoticed until hemostatic stress (i.e. surgery or dental procedure) is
encountered
 patients may require prophylactic desmopressin or infusions of plasma concentrates for
hemostatic challenges (dental surgery)
 Labs
 patients have a normal platelet count
 Plasma protein level is reduced
 Consequently, factor VIII is decreased
 prolonged PTT
 vWF disease, Hemophilia A (Factor VIII) and Hemophilia B (Factor IX)
 Von Willebrand Disease:
 Type 1
 Autosomal dominant disease of mild-moderate deficiency
 Quantitative defect
 Most common subtype (70%)

 Usually a point mutation that leads to problems with protein maturation or that causes
rapid protein clearance from plasma (incomplete penetrance)
 PTT may be prolonged
 Type 3
 Autosomal recessive disease with very low levels and correspondingly severe clinical
manifestations
 Quantitative defect
 Factor VIII stability is affected
 May resemble hemophilia
 Usually a frameshift or deletion mutation involving both alleles
 PTT may be prolonged
 Severe clinical manifestation: hemarthrosis (bleeding into joints) may be seen
 Type 2
 Autosomal dominant disease with normal protein amounts expressed
 Qualitative defect
 Missense mutations → defective multimer assembly (lack of large and intermediate
multimers in plasma)
 25% of all cases
 Mild-moderate bleeding
 Treatment
 Predominantly supportive treatment
 May administer cryoprecipitate (replaces vWF) or DDAVP (causes release of vWF from
endothelium)
 Hemophilia A
 Definition
 Factor VIII deficiency
 Factor VIII is an essential cofactor for Factor IX in the coagulation cascade
 Most common hereditary disease associated with life threatening bleeding
 % of patients based on severity
 Severe disease: < 1%
 Moderate-severe disease: 25%
 Mild disease: 6-50% (6-25% per Hubbard)
 Mutations
 Most severe: X chromosome inversion = no synthesis
 X-linked recessive (mostly male or unfavorably lyonized females)
 Point mutation can lead to no activity, but normal protein levels on immunoassay
 *Risk of bleeding corresponds to degree of deficiency
 Clinical
 Easy bleeding and bruising
 Hematomas
 Bleeding into soft tissue and muscles
 Increased risk of bleeding during and after surgery
 Spontaneous hemorrhage in regions of the body normally subject to trauma
(hemarthroses) that can lead to progressive, crippling deformities. patients may have 1-
2 "target joints"
 No petechiae is characteristic
 Prolonged PTT, normal PT -- point to abnormality in the intrinsic coagulation pathway

 tendency of hemophiliacs to bleed at particular sites (joints, muscles, and the central
nervous system)
 Treatment
 Recombinant factor VIII infusions (replace what is missing)
 15% develop antibodies that bind and inhibit factor VIII
 Prior to development of recombinant factor VIII, patients received plasma from HIV
patients, dooming an entire generation of patients
 Prophylaxis prior to surgery
 Hemophilia B (Christmas Disease)
 Definition
 Factor IX deficiency
 X-linked recessive disease clinically identical to hemophilia A
 Prolonged PTT, normal PT -- abnormality in the intrinsic coagulation pathway
 Diagnosis
 Assay of factor levels
 Treatment
 Recombinant factor IX (replace what is missing)
 Disseminated Intravascular Coagulation (DIC)
 Definition
 Acute, subacute or chronic thrombo-hemorrhagic disease
 Excessive activation of coagulation and formation of thrombi in the microvasculature of
the body = consumption of platelets (thrombocytopenia), fibrin, coagulation factors
 Fibrinolysis activation
 Signs and symptoms:
 Tissue hypoxia, infarction (due to microthrombi), hemorrhage (due to factor depletion +
fibrinolytic mechanism activation)
 Thromboplastic Substances (or tissue factor) into circulation
 May be derived from obstetric complications, damaged tissue following trauma, burns
or surgery, granules of leukemic cells in acute promyelocytic leukemia, mucus from
adenocarcinomas
 Sepsis: endotoxins activate monocytes to release TNFα
 Increased tissue factor expression
 Decreased thrombomodulin expression
 = activation of clotting system + inhibition of coagulation control
 Endothelial Injury
 Initiates tissue factor release from endothelial cells
 Promotes platelet aggregation
 Activates the intrinsic coagulation pathway via exposure of subendothelial connective
tissue
 Injury may occur due to Antigen/Antibody complex deposition (SLE), hypoxia, acidosis,
temperature extremes (heatstroke, burns), infections (meningococci, rickettsiae)
 Consequences
 Widespread deposition of fibrin in microcirculation == thrombosis; consumption of
platelets --> bleeding

 Ischemia
 Microangiopathic hemolytic anemia (RBC fragmentation as the pass through narrow
vessels)
 Hemorrhagic diathesis due to consumption of platelets and clotting factors + the
activation of plasminogen
 Plasmin cleaves fibrin and digests factors V and VII
 Fibrinolysis products inhibit platelet aggregation, fibrin polymerization and thrombin
 Morphology
 Thrombi can affect the brain, heart, lungs, kidneys, adrenals, spleen, and liver
 Bilateral renal cortical necrosis can occur
 May resemble ARDS if pulmonary vasculature is involved
 Adrenals: Waterhouse-Friderichsen syndrome
 "In meningococcemia, fibrin thrombi within the microcirculation of the adrenal
cortex are the probable basis for the massive adrenal hemorrhages seen in
Waterhouse-Friderichsen syndrome"
 Giant hemangiomas: Kasabach-Merritt syndrome (thrombi form in neoplasms because
of stasis and recurrent trauma to fragile blood vessels)
 Causes
 Most commonly due to obstetric complications (50%)
 procoagulants derived from the placenta, dead retained fetus, or amniotic fluid
may enter circulation
 Most cases resolve with delivery of the fetus
 Commonly involves bleeding complications
 Rapid onset
 Carcinomatosis (33%)
 Commonly involves thrombosis complications
 Insidious (slow) onset
 Acute vs. chronic presentation
 Acute DIC: associated with obstetric complications or major trauma; dominated by
bleeding diathesis
 Chronic DIC: associated with carcinomatosis; tends to present with thrombotic
complications
 Clinical
 Microangiopathic hemolytic anemia
 bleed from every orifice
 Respiratory signs and symptoms (dyspnea, cyanosis, respiratory failure)
 Neuro signs and symptoms (convulsions, coma)
 Oliguria and acute renal failure
 Circulatory failure and shock
 Prognosis and Treatment
 Variable prognosis based on underlying disorder
 Remove or treat the underlying cause -- quickly
 well established DIC is a death sentence
COMPLICATIONS OF
TRANSFUSIONS_______________________

 FIVE types of reactions
 Febrile non-hemolytic reaction
 Fever and chills ± dyspnea
 Occurs within six hours of a transfusion of red cells or platelets
 Likely inflammation reaction due to donor leukocytes
 Increased frequency related to length of storage of product
 Signs and symptoms respond to antipyretics and are short lived
 Allergic reactions
 Severe and potentially life threatening if patient has been sensitized to the given
antigens
 Most common in patients with IgA deficiency
 IgG antibodies recognize IgA in the blood product
 IgE antibodies may cause an urticarial reaction
 Mild, and most patients respond to antihistamines allowing the process to continue
 Hemolytic reactions
 Acute Hemolytic Reaction
 Usually due to preformed IgM antibodies against donor red cells that fix
complement
 GM makes Classic Cars -- IgM and IgG activate the classical pathway of
complement
 Likely due to human error (ABO incompatibility)
 Induce complement mediated lysis, intravascular hemolysis, and hemoglobinuria
 Rapid onset: fever, chills, shaking and flank pain due to complement activation,
not RBC lysis
 May rapidly progress to DIC, shock, acute renal failure or death
 (+) direct Coombs test
 Delayed Hemolytic Reaction
 Due to IgG antibodies against a red cell antigen the patient was previously
sensitized to
 (+) direct Coombs test
 Labs typical of hemolysis (Decreased haptoglobin, increased LDH)
 haptoglobin takes up free hemoglobin; therefore, haptoglobin is decreased
when hemoglobin is increased in the serum in things like hemolysis
 antibodies to Rh, Kell, Kidd can activate complement and produce fatal reactions
(similar to ABO mismatches)
 antibodies that do not fix complement → red cell opsonization, extravascular
hemolysis, spherocytosis (minor signs and symptoms)
 Infectious complications
 Bacterial causes are often due to skin contamination at time of donation
 Platelets >> RBCs because platelets must be stored at room temperature
 Signs and symptoms resemble hemolytic and nonhemolytic reactions → may start
broad spectrum antibiotics
 Viral causes are less frequent due to screening
 Infection may occur if donor is acutely infected but viral DNA is not yet detected with
nucleic acid testing (HIV, Hepatitis C, Hepatitis B, (also prions)
 frequent donors or IV drug users who donate and get past the screening; lab error
 Transfusion-related acute lung injury (TRALI)
 Definition

 Severe, often fatal event of factors in transfused blood activating neutrophils in
the lung microvasculature
 More frequent in patients with lung disease
 Two hit model
 Pathogenesis
 Transfused antibodies attack neutrophils
 FFP and platelets contain more antibodies and are more likely to lead to this
complication
 Donations to multiparous women with exposure to multiple MHCI Antigens has a
high risk
 Identify donor product because likely to occur in other patients receiving the
product
 Clinical
 Dramatic, rapid onset of respiratory failure during or soon after a transfusion
 patient has diffuse bilateral pulmonary infiltrates
 Fever, hypotension, hypoxemia
 Prognosis and treatment
 Unresponsive to diuretics
 Treatment: supportive
 Prognosis: guarded (5% mortality if uncomplicated, 6-7% mortality in complicated
cases)
Hubbard
Stuff________________________________________
__
 Antithrombin III (AT III) Deficiency
 Definition
 Deficiency of a serine protease that functions to inhibit thrombin activation
 Increased conversion of prothrombin into thrombin (hypercoagulable state)
 Cofactor: heparin (amplifies activity)
 Clinical
 Variable presentation
 Early death to recurrent pulmonary emboli
 Recurrent lower extremity thrombophlebitis and DVT, venous insufficiency, chronic leg
ulcers
 50% of patients have a DVT or PE by age 30
 Pregnant women have a significantly increased risk of DVT due to hypercoagulable state
 Diagnosis
 < 50% normal activity
 Treatment
 Prophylactic with anticoagulants
 warfarin/coumadin
 heparin if you're pregnant
 heparin activated anti-thrombin III
 Patient with DVT? Heparin in HIGH doses

 Replacement therapy for DVT patients that do not respond to heparin
 Deficiency of Protein C & S
 Present similar to ATIII deficiency
 Recommended that patients are on warfarin to decrease risk of thromboembolic disease
 These proteins are depleted prior to other coagulation factors so there is a temporary
increase in coagulation (as they are anticoagulant molecules)!!
 Vitamin K dependent enzymes
 C: inactivates factors V, VIII
 S: cofactor of C
 Factor V Leiden (nee Activated Protein C Resistance)
 Definition
 Abnormality of this factor at the binding site for protein C
 Heterozygotes: increased risk of thromboembolic disease
 Homozygotes: Excessively high increase for thromboembolism
 Treatment
 No prior episodes: monitor, DVT prophylaxis + risk reduction
 Prior episode: lifelong anticoagulation (if it was an unprovoked episode)
 Prothrombin 20210
 Definition
 G-A mutation resulting in increased activity for prothrombin
 Inability to deactivate prothrombin
 Significant risk of thrombosis
 Treatment:
 No prior episodes: monitor, DVT prophylaxis + risk reduction
 Prior episode: lifelong anticoagulation (if it was an unprovoked episode)
 Antiphospholipid Syndrome
 formerly known as
 anticardiolipin antibody syndrome
 lupus anticoagulant
 don't have to have lupus to have antiphospholipid
 it's not an anticoagulant, it’s a procoagulant -- thrombosis is major feature of
disease
 false positive VDRL antibody syndrome
 Definition
 Circulating antibodies to phospholipid
 Diagnosis
 Prolonged phospholipid-dependent coagulation test (PTT) -- along with vWF,
Hemophilia A and B
 Lack of correction in 1:1 mixing studies with normal plasma
 DRVVT (Dilute Russell Viper Venom Time) may be more specific than PTT
 Clinical
 Thromboembolism
 Miscarriage
 Cerebral ischemia, recurrent stroke (especially in young patients!)

 UBO (unidentified bright objects) on MRI
 Connective tissue disease (seen in 50% of patients
 Prolonged PTT (not corrected with mixing studies)
 Valvular heart disease or CAD in some patients
 Treatment
 No benefit from anticoagulation unless the patient has a history of thromboembolic
disease
 With a history of multiple positive tests over 3-12 months
 Lifelong anticoagulation.
 If necessary during pregnancy: SQ heparin
 Hydroxychloroquine (malaria drug) may reduce thromboembolism in some
patients with APS and SLE
 1:1 Mixing Test
 patient has a prolonged clotting time
 Is something interfering with the test or is the patient missing clotting factors?
 Equal amounts of patients serum + test serum
 Clotting time corrects: patient is missing something
 Type 1 vWF disease
 Hemophilia A (VIII) and B (IX)
 Clotting time is not corrected: patient serum contains an entity that interferes with
clotting
 eg antiphospholipid syndrome

Robbins- Chapter-14-Red-Blood-Cells.pdf

More Related Content

What's hot

Similar to Robbins- Chapter-14-Red-Blood-Cells.pdf

Recently uploaded

Robbins- Chapter-14-Red-Blood-Cells.pdf