X-linked sideroblastic anemia results from a defect in the δ-ALA synthase gene causing defective enzyme production and laboratory findings similar to acquired sideroblastic anemia. It is treated with pyridoxine and blood transfusions if severe. β-thalassemia results from mutations reducing β-globin chain production, causing imbalanced globin ratios and hemolytic anemia. Trait forms show mild anemia while major requires transfusions. Normocytic anemias are categorized by corrected reticulocyte count; common causes include anemia of chronic disease, blood loss, aplastic anemia, and malignancy. Hemolytic anemias show increased reticulocytes and

1. Hematology
Dr. Okon, MRCS

2. X-Linked Sideroblastic Anemia
 X-Linked Sideroblastic Anemia: Inherited
sideroblastic anemia is an X-linked recessive
disorder
 Results from a defect in the δ-ALA synthase
gene, producing a defective enzyme.
 Laboratory findings will be similar to those seen
in acquired sideroblastic anemia
 Treated with pyridoxine (vitamin B6) and, in
severe anemia, may require support with blood
transfusions.

3. β-Thalassemia
 Β-Thalassemia
 Prevalent in Mediterranean populations.
 Chromosome 11 - β-globin chains.
 Mutations result in decreased or absent production of β-globin chains,
leading to an imbalance in the ratio of α- and β-globin production.
 Decrease or cessation in the production of HbA (requires β-globin
chains) and increased aggregation of α-globin chains inside the RBC.
 Absence of β-globin, partner α-globin chains will tetramerize and
precipitate inside RBC precursors while still in the bone marrow, not
allowing RBC maturation.
 β-Thalassemia trait (β/ββ+ or β/β0) - milder form of β-thalassemia,
in which only one gene (heterozygote) is defective, resulting in mild
microcytic anemia.
 Prevalence is high in the Mediterranean population because of
protective effects against Plasmodium falciparum malaria.

4.  Laboratory Findings in β-Thalassemia Trait:
 Decreased Hb, Hct, and MCV
 Normal iron studies, normal RDW (differentiates it from IDA), increased RBC
count
 Hb electrophoresis
 Mildly decreased HbA levels
 Mildly increased HbA2 levels
 Mildly increased HbF levels
 Treatment: Not usually actively treated, given mild symptoms. Monitor
frequently for iron overload caused by an increase in intestinal iron
absorption seen in all forms of β-thalassemias. Do not treat with iron

5.  β-Thalassemia major (β0/β0, β0/β+, β+/β+), also known as Cooley
anemia, results from mutations in both β-globin genes.
 RBCs will have increased amounts of α-globin chains leading to the
tetramerization of α-chains, precipitation of tetramers, and destruction
of some of the RBC precursors in the bone marrow (ineffective
erythropoiesis).
 Extramedullary hematopoiesis
 RBCs that make it into the circulation are severely distorted in shape
and are removed by macrophages in the spleen, leading to severe
hemolytic anemia.
 Patients require lifelong transfusions.

6.  Laboratory and Physical Examination Findings in β-Thalassemia
Major:
 Hb, Hct, and MCV are decreased.
 RDW and reticulocytes are increased.
 Patients are at risk of hemosiderosis (iron overload) from constant
transfusions.
 Patients will have high levels of unconjugated bilirubin and show
signs of jaundice (from hemolysis).
 Hb electrophoresis will indicate the following:
 Absence of HbA production
 Significant increase in HbF levels
 Increased HbA2 levels
 Splenomegaly may be present.
 Radiographs may show a crew cut appearance of the skull. You may
also see skeletal deformities caused by extramedullary
hematopoiesis

7.  Treatment:
 Chronic blood transfusions
 Iron chelation treatment to prevent iron overload
 Splenectomy in patients with splenomegaly

 Bone marrow transplantation is the only cure. It
is indicated only in patients with severe disease.

8. Normocytic Anemias
 Subdivided into those that have an
inappropriate corrected reticulocyte count
(<3%) and those with an appropriate corrected
reticulocyte count.
 Most common type of normocytic anemia is
anemia of chronic disease.
 Normocytic anemias with a corrected
reticulocyte count lower than 3% include early
ACD or IDA, acute blood loss, aplastic anemia,
chronic kidney disease (CKD), and malignancy

9.  Normocytic anemias with a corrected
reticulocyte > 3%
 Intrinsic or extrinsic hemolytic anemias
 sickle cell disease,
 glucose-6-phosphate dehydrogenase (G6PD)
deficiency,
 pyruvate kinase (PK) deficiency
 hereditary spherocytosis
 hereditary elliptocytosis
 paroxysmal nocturnal hemoglobinuria (PNH)
 HbC disease
 immune hemolytic anemias
 microangiopathic and macroangiopathic hemolytic

10.  Intravascular hemolysis refers to RBC breakdown that occurs
primarily within the blood vessels.
 Hallmark of intravascular hemolysis is the spilling of RBC contents
into the bloodstream, namely the release of free Hb and lactate
dehydrogenase (LDH).
 Free Hb then binds to haptoglobin, and the Hb–haptoglobin complex
is rapidly removed by the liver, causing a drop in plasma levels of
haptoglobin.
 Patients develop dark urine from the spilling of free Hb into the urine
(hemoglobinuria).
 Intravascular hemolysis is characterized by high LDH and low
haptoglobin levels.

11.  Extravascular hemolysis refers to RBC
breakdown that occurs primarily by the
macrophages of the reticuloendothelial system
in the liver, spleen, lymph nodes, and bone
marrow.
 No direct release of RBC contents into the
bloodstream.

12. Normocytic Anemias With Corrected
Reticulocyte Count < 3%
 Acute Blood Loss: internal and external bleeding.
 Most common cause of hypovolemic shock. Patients usually present
with sudden signs of anemia (weakness, fatigue, pallor, dyspnea) and
have a history of trauma or bleeding disorders.
 Laboratory Findings in Acute Blood Loss
 Hb and Hct are initially normal but decrease as interstitial fluid shifts
into the vascular compartment resulting in hemodilution; MCV is
normal.
 Reticulocyte will not be increased more than 3% until 1 week after the
precipitating event

13.  Treatment:
 Intravenous fluid replacement
 Blood transfusion (depending on severity)
 Correcting the cause of the hemorrhage

14. Aplastic Anemia
 A disorder in which the bone marrow does not produce the
appropriate amount of new cells to replenish blood cell turnover.
 Characterized by pancytopenia or decreased amounts of all three
bloodlines (RBCs, WBCs and platelets) and decreased reticulocyte
count (reticulocytopenia).
 Etiology
 Idiopathic (most common; confers poor prognosis)
 Drugs (most common known cause; has better prognosis)—
chloramphenicol, alkylating agents, antimalarials, sulfonamides
 Exposure to chemical agents—benzene, DDT (insecticide)
 Infection (usually viral)—parvovirus B19, Epstein-Barr virus (EBV),
HIV, hepatitis C
 Whole-body ionizing radiation

15.  The presentation is often gradual and depends on which blood cell line
becomes critically deficient first.
 Anemia—decreased RBCs lead to fatigue, malaise, and pallor.
 Thrombocytopenia—decreased platelets lead to petechiae (pinpoint red
or purple spots on skin), purpura (nonblanching purple spots bigger than
petechiae), and mucosal bleeding.
 Neutropenia—decreased neutrophils lead to infections.
 Laboratory Findings:
 Decreased RBC, WBC, and platelet count
 Hypocellular bone marrow and fatty infiltration on bone marrow biopsy

16.  Treatment:
 Discontinuation of the offending agent.
 Antibiotics if infection present
 RBC transfusion (if severe anemia)
 Platelet transfusion (if severe thrombocytopenia)
 Immunosuppressive therapy with antithymocyte
globulin (ATG) or cyclosporine
 Granulocyte colony-stimulating factor (G-CSF) and
granulocyte-macrophage colony-stimulating factor
(GM-CSF)
 Allogeneic hematopoietic stem cell transplantation
(bone marrow transplant with cells from another
individual)

17. Chronic Kidney Disease
 EPO deficiency leads to decreased
hematopoiesis.
 Laboratory Findings:
 Decreased Hb and Hct, normal MCV
 Burr cells on peripheral smear
 Thrombocytopenia; the buildup of toxic metabolites
caused by kidney failure results in a functional
platelet defect
 Prolonged bleeding time caused by a reversible
platelet aggregation defect (reversible with dialysis)

18.  Malignancy:
 Malignancy-related anemia is classified in three
main categories:
 RBC losses from the body (e.g., intestinal blood
loss in colon cancer)
 Increased RBC destruction (e.g., immune hemolytic
anemia seen in chronic lymphocytic leukemia)
 Decreased red blood cell production (e.g., cancer
metastasis to the bone marrow)
 Myelophthisic anemia refers to the
displacement of normal marrow cells by
metastatic cancer cells.

19. Normocytic Anemias With Corrected
Reticulocyte Count More Than 3%
 Sickle cell anemia:
 Autosomal recessive disorder that leads to a structural or
qualitative abnormality of Hb and is associated with hemolysis
 Common in African and African American populations.
 Point mutation in the β-globin gene substitutes a valine for
glutamic acid at position 6 (Glu-6-Val) and leads to the
production of abnormal HbS.
 Deoxygenated form of HbS can reversibly polymerize with other
HbS molecules. The higher concentration of deoxygenated HbS
in the RBCs results in a greater rate of polymerization. The
polymerization of HbS inside RBCs leads to sickle-shaped cells,
which are subject to destruction by the spleen.
 Sickling also increases the blood’s viscosity, leading to
microvascular occlusion. Sickle cell disorder appears in different
forms, each with a differing severity of anemia.

20.  Sickle Cell Trait
 Patients are heterozygous, having one copy of the HbA and HbS
allele.
 Genotype is HbSA. The concentration of deoxygenated HbS in these
patients is approximately 40% of total Hb and rarely reaches the
threshold concentration necessary to initiate pathologic
polymerization of HbS inside RBCs.
 Benefit from the protective effects against P. falciparum malaria that
result from this mutation.
 Laboratory Findings:
 These patients are not anemic. Hb, Hct, and MCV are normal.
Peripheral smear is also normal.
 Hb electrophoresis findings include the following:
 Presence of HbS.
 Decreased HbA levels.
 HbF and HbA2 levels do not change

21. Sickle Cell Disease
 Homozygous, having two copies of the HbS
allele. The genotype is HbSS.
 Triggers - Acidosis and hypoxia cause Hb to
release bound oxygen, increasing the
concentration of deoxygenated HbS in RBCs.
 Damage to the RBC membrane impairs Na+/K+
and water homeostasis, leading to cellular
dehydration and increased sickling of RBCs.

22. Signs and Symptoms
 Pain crises occur beginning at age 1 or 2 years.
 Vascular occlusion can lead to organ dysfunction or failure, causing bone infarcts,
avascular necrosis,
 Acute chest syndrome (chest pain, shortness of breath [SOB], and pulmonary
infiltrates on chest radiograph), chronic leg ulcers, osteomyelitis (salmonella), and
stroke.
 Dactylitis (hand-foot syndrome) or swelling of hands and feet can be seen in infants.
 Recurrent splenic infarction and autosplenectomy occur at a young age. The
presence of HowellJolly bodies on a peripheral smear signifies impaired or absent
splenic function. Loss of splenic function makes patients increasingly susceptible to
infection by encapsulated bacteria, and daily antibiotic prophylaxis is required for the
treatment of children.
 Aplastic crisis can occur in association with parvovirus B19.
 Sequestration crisis results when there is entrapment of sickled RBCs in the spleen,
resulting in rapid splenomegaly.
 Renal papillary necrosis can occur when microinfarcts of the kidney result in
microhematuria.

23.  Laboratory Findings:
 Decreased Hb and Hct
 Normal MCV
 Increased reticulocyte count
 Crescent-shaped RBCs, target cells, and Howell-
Jolly bodies on peripheral smear
 Sickle cell screen with sodium metabisulfite–
induced sickling of cells

24.  Hb electrophoresis results as follows:
 Absence of HbA
 Increased levels of HbS
 Increased HbF levels

 Plain radiographs of the skull may show a crew
cut appearance caused by extramedullary
hematopoiesis, as also seen in thalassemias

25.  Factors That Prevent or Reverse Sickling (and Treatments):
 Avoidance of hypoxia and dehydration can prevent sickling.
 Increased levels of HbF inhibit HbS polymerization and prevent sickling.
Hydroxyurea has been shown to increase HbF levels and is used in
patients with frequent sickle cell crises. Newborns are often
asymptomatic because of high levels of HbF.
 Morphine can provide pain relief.
 Exchange transfusion can be used to treat serious forms of vascular
occlusion (e.g., acute chest syndrome, stroke, priapism).
 Allogeneic stem cell transplantation is curative in patients with severe
clinical disease.
 All patients with sickle cell disease must be up to date on their
immunizations (pneumococcal, meningococcal vaccine, Hib, hepatitis B,
and influenza vaccines).
 Patients with sickle cell disease should receive folic acid
supplementation.

26. G6PD Deficiency
 G6PD, an enzyme that protects RBCs from oxidant stress
 This enzyme deficiency leads to decreased synthesis of NADPH (a
reduced form of nicotinamide adenine dinucleotide phosphate) and
glutathione (antioxidants) from the pentose phosphate pathway.
 NADPH helps restore glutathione stores so that glutathione can then
reduce reactive oxygen species (H2O2) to less harmful compounds
(H2O).
 Hemolysis is mostly intravascular, but some extravascular hemolysis
is also seen.


27.  Increased stress leads to the oxidation of Hb inside RBCs, and
Hb molecules precipitate to form Heinz bodies. Intravascular
hemolysis results because Heinz bodies damage the RBC
membrane and make RBCs more susceptible to lysis in the
circulation. RBCs that do not lyse while in circulation are
removed by the spleen, leading to extravascular hemolysis.
G6PD deficiency is an X-linked recessive disorder common in
black, Middle Eastern, and Mediterranean populations.
 Protective against P. falciparum malaria.
 Hemolysis often results from exposure to oxidative stress, such
as the following:
 Infection (most common)—acute viral or bacterial infections

28.  Drugs—sulfonamides (trimethoprim-sulfamethoxazole), dapsone,
primaquine, chloroquine, nitrofurantoin
 Acidosis (e.g., diabetic ketoacidosis [DKA])
 Fava beans (historically, this condition was called favism)

 Signs and Symptoms:
 Most are asymptomatic
 History of neonatal jaundice and cholelithiasis
 Episodic signs of anemia (possibly associated with jaundice and
splenomegaly)

 Laboratory Findings:
 Decreased Hb and Hct, normal MCV
 Heinz bodies and/or bite cells on peripheral smear

29.  Measure G6PD enzyme activity after a
hemolytic attack. The value will be decreased. It
may be falsely elevated or normal in times of
hemolysis.

30. Pyruvate kinase deficiency.
 Pyruvate kinase deficiency.
 Autosomal recessive disorder that causes chronic lack of ATP in
RBCs. PK is an enzyme in the glycolytic pathway that helps
synthesize ATP. Because RBCs can only produce ATP via glycolysis,
they are dependent on the proper function of the PK enzyme for
energy
 Lack of ATP results in accelerated RBC membrane damage and
dehydration. It is characterized by chronic extravascular hemolysis
with poikilocytosis (RBCs of abnormal shape) and cellular
dehydration on blood smear.
 Patients may present with hemolytic anemia with jaundice since birth.
 Laboratory Findings:
 Hb and Hct are decreased; MCV is normal.
 Echinocytes are present on peripheral smear.
 Measure direct PK enzyme activity to diagnose.
 Treatment: Most patients do not require treatment. Splenectomy may
be beneficial in patients with severe disease.

31. Hereditary spherocytosis (HS)
 Autosomal dominant hemolytic anemia that results from an
abnormality in the RBC membrane.
 Characterized by defects in membrane proteins such as ankyrin
(most common), spectrin, or band 3. RBCs lose their characteristic
biconcave shape and instead have a spherical appearance.
 Spherical shape is less versatile and deformable in circulation,
resulting in RBCs becoming trapped and removed in the spleen.
 Signs and Symptoms:
 Patients can be asymptomatic until adulthood.
 Anemia, increased unconjugated bilirubin (jaundice), increased
incidence of cholelithiasis (pigment gallstones)


32.  Laboratory Findings:
 Hb and Hct are decreased; MCV is normal.
 MCHC is increased (characteristic of this disease on step 1).
 Osmotic fragility test will show increased lysis of RBCs in hypotonic
solution.
 Spherocytes are present on peripheral smear.
 Treatment:
 Splenectomy (decreases entrapment and destruction of spherocytes
in the spleen) is curative but only indicated for patients with severe
disease, given the increased risk of infection with encapsulated
organisms.
 Blood transfusion is used in patients with severe disease.
 Patients must be on folate and iron supplementation given the chronic
hemolytic state.

33. Hereditary Elliptocytosis (HE)
 Autosomal dominant disorder that results from
defects in the membrane protein spectrin (most
common) and band 4.1.
 Signs and symptoms are similar to HS but
generally milder (with most patients having no
anemia).
 Peripheral blood smear will show elliptocytes.
Hemolysis is caused by RBC destruction in the
spleen (will result in splenomegaly).
 Splenectomy is curative in symptomatic
patients.


34. Paroxysmal Nocturnal
Hemoglobinuria (PNH)
 PNH results from a rare acquired intrinsic defect in
 the RBC cell membrane that increases the susceptibly of RBCs to complement-mediated
hemolysis.
 Normal RBCs have glycosylphosphatidylinositol (GPI) linkage or decay-accelerating factor
(DAF)
 proteins on their cell membrane, which act to protect the cell from destruction by the
complement
 system. DAF helps disrupt formation of the membrane attack complex and prevents C9 from
binding
 to the RBCs. Without these protective proteins on their cell surface, RBCs become easy targets
for
 destruction by the complement system, and intravascular hemolysis ensues. Complement
attachment
 to RBCs is potentiated in acidotic situations; therefore, there is increased hemolysis at night
when
 respiratory acidosis ensues because of the physiologic decrease in respiratory rate while
sleeping.
 PNH usually occurs in the second decade of life and the incidence increases with age. Platelets
and
 granulocytes can also be affected by this disease. Patients with this disease are at increased
risk of
 developing aplastic anemia and acute leukemia.
 Signs and Symptoms:

35.  Clinical and Laboratory Findings:
 m Triad of Coombs negative hemolytic anemia with pancytopenia and
venous thrombosis
 m Usually normal MCV but can be microcytic (low MCV) because of
long-standing loss of iron in
 urine (via loss of Hb and hemosiderin in urine)
 m Iron deficiency caused by hemoglobinuria and hemosiderinuria
 m Increased incidence of venous thrombosis
 l The intravascular destruction of platelets results in release of their
prothrombotic intracellular
 granules into the circulation.
 m Decreased serum haptoglobin (caused by intravascular hemolysis)
 m Low leukocyte alkaline phosphatase (LAP) score

 Treatment:
 m Correct the anemia and prevent thrombosis.
 m Eculizumab is a monoclonal antibody that acts as a terminal

36. Hemoglobin C (HbC) Disease
 autosomal recessive mutation
 in β-globin chain leading to extravascular hemolysis. An abnormal
hemoglobin structure is formed by
 the substitution of glutamic acid with lysine at position 6 of the β-globin chain
(sickle cell is a glutamic
 acid to valine substitution at the same position). The Hb in HbC is less
soluble than HbA and forms
 hexagonal crystals inside RBCs. HbC does not polymerize as readily as HbS
(sickle cell disease) and will
 produce less sickling of RBCs. The HbC mutation causes the RBC to lose
plasticity, thereby leading to
 mild extravascular hemolytic anemia in homozygotes (HbCC). Patients with
sickle cell–hemoglobin
 C (HbSC) have the gene for HbS inherited from one parent and the gene for
HbC from the other parent.
 HbSC patients will have only a few sickle cells and thereby have milder
disease than HbSS patients.
 Signs and Symptoms:
 m Most people have no symptoms.

37.  Clinical and Laboratory Findings:
 m Mild extravascular hemolysis in homozygotes
or HbCC (people with HbC trait [HbAC] are
 phenotypically normal)
 m Peripheral smear with HbC crystals seen in
RBCs; will also see target cells
 m Mild splenomegaly
 m Mild anemia
 Treatment:
 m Usually no treatment is needed, but patients
may supplement with folate to improve anemia.