Hereditary hemolytic anemias can be caused by defects in the red blood cell's hemoglobin, membrane, metabolic machinery or enzymes. Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzyme defect causing hemolytic anemia. It results from a lack of the enzyme G6PD, which protects red blood cells from oxidative damage. Patients with G6PD deficiency typically present with neonatal jaundice or acute hemolytic anemia triggered by factors like fava beans, infections or drugs. An acute hemolytic episode is characterized by symptoms like jaundice and dark urine over hours to days, along with signs of intravascular and extravascular hemolysis on lab tests.

1. Hemolytic anemia
Dr. AJMEL. P. MOHAMMED

2. Anemia classification
classification of anemias is in three groups:
(1) decreased production of red cells,
(2) increased destruction of red cells, and
(3) acute blood loss.

3. patients who are anemic as a result of either
•increased destruction of red cells or
•acute blood loss
Both have one important element in common:
the anemia results from overconsumption of red cells from the peripheral blood, whereas
the supply of cells from the bone marrow is normal (indeed, it is usually increased).
these two groups differ in
•physical loss of red cells from the bloodstream or from the body itself, as in acute
hemorrhage,
•destruction of red cells within the body, as in hemolytic anemias.

4. HEMOLYTIC ANEMIA

5. Heriditary vs acquired hemolytic anemia
Hereditary
causes correlate with intracorpuscular
defects, because these defects are due to
inherited mutations;
the one exception is PNH, because the
defect is due to an acquired somatic
mutation.
Acquired
causes correlate with extracorpuscular
factors, because mostly these factors are
exogenous;
the one exception is familial hemolytic
uremic syndrome (HUS; often referred to as
atypical HUS), because here an inherited
abnormality allows complement activation
to be excessive, with bouts of production of
membrane attack complex capable of
destroying normal red cells

6. Features of hemolytic disorder

7. Triad of hemolytic anemia
The diagnosis of hemolytic anemia is usually not difficult,
the triad of
• normomacrocytic anemia,
• reticulocytosis, and
• hyperbilirubinemia.

8. Compensated vs decompensated hemolysis
Redcell destructionis apotent stimulus for erythropoiesis, whichis mediatedby erythropoietin(EPO)
producedby the kidney.
This mechanismis soeffective that inmany cases the increasedoutput of redcells fromthe bone marrow can
fully balance an increaseddestructionof redcells. Insuchcases, we say that hemolysis is compensated.
there is no anemia•
patient witha hemolytic condition, evenaninheritedone, may present without anemia;and•
pregnancy,□
folate deficiency, or□
renal failure interfering withadequate EPO production.□
acute infection, depresseserythropoiesis□
i.e., anemia may suddenly appear, incertaincircumstances, for instance in○
compensatedhemolysis may become “decompensated,”•
compensatedhemolysis
which may cause a rather precipitous fall inhemoglobin
— an occurrence sometimes referredtoas aplastic crisis.
dramatic example is infection by parvovirusB19,

9. A. Inherited hemolytic anemias
INHERITED HEMOLYTIC ANEMIAS
There are three essential components in the red cell:(intracorpuscular)
(1) hemoglobin,
(2) the membrane-cytoskeleton complex, and
(3) the metabolic machinery necessary to keep hemoglobin and the
membrane-cytoskeleton complex in working order.
Extracorpuscular : Familial (atypical) hemolytic uremic syndrome

10. 1. Intracorpuscular inherited hemolytic anemia

11. a. Hemoglobinopathies

12. b. Membrane defects
 The membrane-cytoskeleton complex is so integrated that, not surprisingly,
• an abnormality of almost any of its components will be disturbing or disruptive, causing structural
failure, which results ultimately in hemolysis.
• These abnormalities are almost invariably inherited mutations; thus, diseases of the membrane-
cytoskeleton complex belong to the category of inherited HAs.
 Thus, the majority of the diseases in this group have been known for over a century as
• hereditary spherocytosis and
• hereditary elliptocytosis.
 Over the past 20 years, their molecular basis has been elucidated; it has emerged that both
conditions can arise from mutations in several genes with considerable overlap

14. α-Spectrin RECESSIVE RARE
β-Spectrin DOMINANT RARE
Ankyrin DOMINANT MAJORITY
Band 3 RECESSIVE 25%
α-Spectrin DOMINANT 65%
β-Spectrin DOMINANT 30%
Band 4.1 DOMINANT 5%
Band 4.2 RECESSIVE 3%
HERIDITARY SPHEROCYTOSIS HERIDITARY ELLPTOCYTOSIS

15. Hereditary spherocytosis
 relatively common type of genetically determined HA,
 with an estimated frequency of at least 1 in 5000.
 Its identification is credited to Minkowksy and Chauffard,

 In vitro studies revealed that the
 red cells were abnormally susceptible to lysis in hypotonic media;
 indeed, the presence of osmotic fragility became the main diagnostic test for HS.
 HS, thus defined, is genetically heterogeneous;
 i.e., it can arise from a variety of mutations in one of several genes.
 inheritance of HS is not always autosomal dominant (with the patient being heterozygous);
 some of the most severe forms are instead autosomal recessive (with the patient being
homozygous).

16. HS clinical presenatation
 The spectrum of clinical severity of HS is broad.
 Severe cases
 may present in infancy with severe anemia
 mild cases
 may present in young adults or even later in life.
 The main clinical findings are
• jaundice,
• an enlarged spleen, and
• often gallstones;
 indeed, it may be the finding of gallstones in a young person that triggers diagnostic
investigations.
 In milder cases, hemolysis is often compensated, and this may cause variation in time even in
the same patient, due to the fact that intercurrent conditions (e.g., pregnancy, infection) may cause
decompensation.

17. HS diagnosis
 The anemia is usually normocytic, with the characteristic morphology that gives the disease its name.
 An increased mean corpuscular hemoglobin concentration (MCHC) on an ordinary blood count report
should raise the suspicion of HS,
 because HS is almost the only condition in which this abnormality
occurs.
 When there is a family history, it is usually easy to make a diagnosis based on features of HA and typical red
cell morphology.
 However, there may be no family history for at least two reasons.
• First, the patient may have a de novo mutation, i.e., a mutation that has taken place in a germ cell of one of
his parents or early after zygote formation.
• Second, the patient may have a recessive form of HS. In such cases, more extensive laboratory investigations
are required, including osmotic fragility, the acid glycerol lysis test, the eosin-5′-maleimide (EMA)–binding
test, and SDS-gel electrophoresis of membrane proteins; these tests are usually carried out in laboratories
with special expertise in this area. Sometimes a definitive diagnosis can be obtained only by molecular
studies demonstrating a mutation in one of the genes underlying HS

18. Role of spleen in HS
 It has been apparent for a long time that the spleen plays a special role in HS through a
 dual mechanism.
o On one hand, like in many other HAs, the spleen itself is a major site of destruction;
o on the other hand, transit through the splenic circulation makes the defective red cells more
spherocytic and, therefore, accelerates their demise, even though that may take place
elsewhere.

19. HS treatment
 do not have a causal treatment for HS;
 i.e., no way has yet been found to correct the basic defect in the membrane-cytoskeleton structure.
 Becoz of special role of the spleen: almost obligatory therapeutic measure was splenectomy.
• In mild cases, avoid splenectomy.
• Delay splenectomy until puberty in moderate cases or until 4–6 years of age in severe cases.
• Along with splenectomy, cholecystectomy should not be regarded as automatic;
it should be carried out, usually by the laparoscopic approach, when clinically indicated.

20. Hereditary elliptocytosis
 it is the shape of the red cells that gives the name to the condition, but there is no direct
correlation between the elliptocytic morphology and clinical severity.
 In fact, some mild or even asymptomatic cases may have nearly 100% elliptocytes,
 whereas in severe cases, all kinds of bizarre poikilocytes can predominate.
 Clinical features and recommended management are similar to those for HS.
 Spleen may not have the specific role it has in HS,
in severe cases, splenectomy may be beneficial.

21. Disorders of cation transport
discovered through the incidental finding, in a blood test, of a high serum K+ (pseudohyperkalemia).
 In patients from some families, the cation transport disturbance is associated with
o gain of water; as a result, the red cells are overhydrated (low MCHC), and
o on a blood smear, the normally round-shaped central pallor is replaced by a linear-shaped central pallor,
which has earned this disorder the name stomatocytosis.
 In patients from other families, instead,
o the red cells are dehydrated (high MCHC), and
o their consequent rigidity has earned this disorder the name xerocytosis.
 One would surmise that in these disorders the primary defect may be in a cation transporter;
 indeed, xerocytosis results from mutations in PIEZO1.
 In other patients with stomatocytosis, mutations are found in other genes also related to solute transport,
• including SLC4A1 (encoding band 3),
• the Rhesus gene RHAG, and
• the glucose transporter gene SLC2A1 responsible for a special form called cryohydrocytosis.
 Hemolysis can vary from relatively mild to quite severe.
 it is important to know that in stomatocytosis, splenectomy is strongly contraindicated because it has been
followed in a significant proportion of cases by severe thromboembolic complications.

22. c. Enzymopathies
1. Glycolytic pathway
a. HK
b. G6PI
c. PFK
d. ALDOLASE
e. GAPD
f. DPGM
g. PGK
h. PK
2. Redox pathway
a. G6PD
b. GSH
c. GCS
d. Cyt b5
3. Nucleotide metabolism
a. AK
b. P5N

24. Enzyme deficiencies causing hemolysis;
in the order of frequency
1.G6PD deficiency
2.Pyruvate Kinase deficiency
3.Pyrimidine 5'-nucleotidase (P5N)
4.Glucose 6-phosphate isomerase (G6PI)

25. Abnormalities of glycolytic pathway
Because red cells, in the course of their differentiation,
have sacrificed not only their nucleus and their ribosomes, but also their mitochondria,
they rely exclusively on the anaerobic portion of the glycolytic pathway for producing energy in the form of ATP.
•Most of the ATP is required by the red cell for cation transport against a concentration gradient across the membrane.
•If this fails, due to a defect of any of the enzymes of the glycolytic pathway, the result will be hemolytic disease.

26. Pyruvate kinase deficiency
 Abnormalities of the glycolytic pathway are all inherited and all rare.
 deficiency of pyruvate kinase (PK) is also rare,
 estimated prevalence in most populations of the order of 1:10,000.
 The clinical picture of homozygous (or compound biallelic) PK deficiency is that of an HA that often
• presents in the newborn with neonatal jaundice; the jaundice persists, and
• it is usually associated with a very high reticulocytosis.
• The anemia is of variable severity; sometimes it is so severe as to require regular blood transfusion treatment,
whereas sometimes it is mild, bordering on a nearly compensated hemolytic disorder.
 The delay in diagnosis : the fact that the anemia is remarkably well tolerated,
 because the metabolic block at the last step in glycolysis causes an increase in bisphosphoglycerate (or DPG; a
major effector of the hemoglobin-oxygen dissociation curve; thus, the oxygen delivery to the tissues is enhanced, a
remarkable compensatory feat.

27. Treatment of pyruvate kinase deficiency
 The management of PK deficiency is mainly supportive.
• In view of the marked increase in red cell turnover, oral folic acid supplements should be given
constantly.
• Blood transfusion should be used as necessary
• iron chelation may have to be added if the blood transfusion requirement is high enough to cause iron
overload.
• more severe disease, splenectomy may be beneficial.
• bone marrow transplantation option for severe cases when a sibling donor is available.
• Rescue of inherited PK deficiency through lentiviral-mediated human PK gene transfer has been
successful in mice.
• Prenatal diagnosis has been carried out in a mother who had already had an affected child.

28. Abnormalities of redox system

29. G6PD deficiency
• G6PD is a housekeeping enzyme critical in the redox metabolism of all aerobic cells.
• In red cells, its role is even more critical, because it is the only source of NADPH,
• which directly and via glutathione(GSH) defends these cells against oxidative stress.
• G6PD deficiency is a prime example of an HA due to interaction between an intracorpuscular cause
and an extracorpuscular cause, because in the majority of cases hemolysis is triggered by an
exogenous agent.
• decrease in G6PD activity is present in most tissues of G6PD-deficient subjects,
 in other cells, the decrease is much less marked than in red cells,
 and it does not seem to impact on clinical expression

30. Clinical manifestations of G6PD deficiency
 majority of people with G6PD deficiency remain clinically asymptomatic throughout their lifetime;
 all of them have an increased risk of
1. developing neonatal jaundice (NNJ) and
2. a risk of developing acute HA (AHA) when challenged by a number of oxidative agents.

31. Neonatal jaundice in G6PD deficiency
• NNJ related to G6PD deficiency is very rarely present at birth;
• the peak incidence of clinical onset is between day 2 and day 3, and in most cases, the
anemia is not severe.
• NNJ can be very severe in some G6PD-deficient babies, especially in association with
• prematurity,
• infection, and/or
• environmental factors (such as naphthalene-camphor balls, which are used in babies’
bedding and clothing)
• Severity of NNJ is also increased by the coexistence of a
• monoallelic or biallelic mutation in the uridyl transferase gene (UGT1A1;
• the same mutations are associated with Gilbert’s syndrome).
• If inadequately managed, NNJ associated with G6PD deficiency can produce kernicterus and
permanent neurologic damage

32. Acute hemolytic anemia in G6PD deficiency
 AHA can develop as a result of three types of triggers:
 (1) fava beans (2) infections (3) drugs.
 Typically, a hemolytic attack starts with malaise, weakness, and abdominal or lumbar pain.
 After an interval of several hours to 2–3 days, the patient develops jaundice and often dark urine.
 The onset can be extremely abrupt, especially with favism in children.
 The anemia is
• moderate to extremely severe,
• usually normocytic and normochromic, and
• due partly to intravascular hemolysis;
 hence, it is associated with hemoglobinemia, hemoglobinuria, high LDH, and low or absent plasma haptoglobin.
 The blood film shows
• anisocytosis, polychromasia, and spherocytes typical of hemolytic anemias.
• The most typical feature of G6PD deficiency is the presence of bizarre poikilocytes, with red cells that appear to have
unevenly distributed hemoglobin (“hemighosts”) and red cells that appear to have had parts of them bitten away (“bite
cells” or “blister cells”).
 A classical test, now rarely carried out, is supravital staining with methyl violet, which, if done promptly, reveals the
presence of Heinz bodies (consisting of precipitates of denatured hemoglobin and hemichromes), which are regarded as a
signature of oxidative damage to red cells (they are also seen with unstable hemoglobins).
• LDH is high, and so is the unconjugated bilirubin, indicating that there is also extravascular hemolysis.
• The most serious threat from AHA in adults is the development of acute renal failure (this is exceedingly rare in children).
• full recovery from AHA associated with G6PD deficiency is the rule

33. Drugs causing hemolysis in G6PD deficiency

34. Primaquine and G6PD deficiency
Primaquine (PQ) led to the discovery of G6PD deficiency,
 this drug has not been very prominent subsequently, because it is not necessary for the
treatment of life-threatening P. falciparum malaria.
 Today there is a revival of interest in PQ because
 it is the only effective agent for
o eliminating the gametocytes of P. falciparum (thus preventing further transmission) and
o eliminating the hypnozoites of Plasmodium vivax (thus preventing endogenous relapse).
 G6PD testing ought to be made mandatory before giving this drug because
• fatal cases have been reported in newborns with kidney injury and
• in adults with tumor lysis syndrome.

35. CNSHA in G6PD deficiency
 small minority of subjects with G6PD deficiency have chronic nonspherocytic hemolytic anemia (CNSHA)
of variable severity.
o The patient is nearly always a male,
o usually with a history of NNJ,
o who may present with anemia,
§ Severity: borderline to transfusion dependent.
§ usually normomacrocytic, with reticulocytosis.
o unexplained jaundice, or
o gallstones later in life.
o The spleen may be enlarged.
o Bilirubin and LDH are increased.
 CNHSA, Although hemolysis is, by definition,
• chronic in these patients,
• they are also vulnerable to acute oxidative damage, and therefore the same agents that can cause AHA in people
with the ordinary type of G6PD deficiency will cause severe exacerbations in people with CNSHA associated with
G6PD deficiency.
• CNSHA, the deficiency of G6PD is so severe in granulocytes that it becomes rate-limiting for their oxidative burst,
with consequent increased susceptibility to some bacterial infections.

36. G6PD deficiency treatment
• avoiding exposure to triggering factors of previously screened subjects.
§ screening depend on the prevalence of G6PD deficiency in each individual community.
§ Favism is entirely preventable in G6PD-deficient subjects by not eating fava beans.
§ Drug-induced hemolysis can be prevented by testing for G6PD deficiency before prescribing;
• in most cases, one can use alternative drugs.
• once its cause is recognized, in most cases, no specific treatment is needed.
• if the anemia is severe,
• it may be a medical emergency, especially in children, requiring immediate action, including blood transfusion.
• If there is acute renal failure, hemodialysis may be necessary, but if there is no previous kidney disease, recovery is the rule.
• management of NNJ associated with G6PD deficiency is no different from that of NNJ due to other causes.
• CNSHA, if the anemia is not severe, regular folic acid supplements and regular hematologic surveillance will
suffice.
• avoid exposure to potentially hemolytic drugs, and
• blood transfusion may be indicated when exacerbations occur, mostly in concomitance with intercurrent infection.
• regular blood transfusion may be required, in which case appropriate iron chelation should be instituted.
 Unlike in HS, there is no evidence of selective red cell destruction in the spleen:
 however in practise, splenectomy has proven beneficial in severe cases

37. Other abnormalities of redox system
 GSH is a key player in the defense against oxidative stress.
 Inherited defects of GSH metabolism are exceedingly rare, but each one can give rise to chronic HA.
 A rare, peculiar, usually self-limited severe HA of the first month of life,
called infantile poikilocytosis, may be associated with deficiency of glutathione peroxidase (GSHPX)
due not to an inherited abnormality, but to transient nutritional deficiency of selenium, an element
essential for the activity of GSHPX.

38. Abnormalities of nucleotide metabolism
pyrimidine 5'-nucleotidase (p5n) deficiency P5N
is a key enzyme in the catabolism of nucleotides arising from the degradation of nucleic acids that takes
place in the final stages of erythroid cell maturation.
How exactly its deficiency causes HA is not well understood, but a highly distinctive feature of this
condition is a morphologic abnormality of the red cells known as basophilic stippling.
The condition is rare, but it probably ranks third in frequency among red cell enzyme defects (after G6PD
deficiency and PK deficiency).
The anemia is lifelong, of variable severity, and may benefit from splenectomy.

39. B. Acquired hemolytic anemia
Intracorpuscular Defects Extracorpuscular Factors

40. Intracorpuscular acquired hemolytic anemia

41. PNH
 PNH is an acquired chronic HA characterized by
 persistent intravascular hemolysis subject to recurrent exacerbations.
• hemolysis
• pancytopenia
• tendency to venous thrombosis.
 This triad makes PNH a truly unique clinical condition;
 however, when not all of these three features are manifest on presentation,
 the diagnosis is often delayed, although it can always be made by appropriate laboratory
investigations.
 PNH has about the same frequency in men and women and is encountered in all populations
throughout the world, but it is a rare disease;

 There is no evidence of inherited susceptibility.
 PNH has never been reported as a congenital disease,
 but it can present in small children or as late as in the seventies,
 although most patients are young adults

42. PNH clinical features
 The patient may seek medical attention because, one morning, she or he passed blood instead of urine.
This distressing or frightening event may be regarded as the classical presentation;
 Indeed, the patient often presents simply as a problem in the differential diagnosis of
o anemia, whether symptomatic or discovered incidentally.
o Sometimes, the anemia is associated from the outset with neutropenia, thrombocytopenia, or both,
thus signaling an element of bone marrow failure.
o Some patients may present with recurrent attacks of severe abdominal pain defying a specific
diagnosis and eventually found to be related to thrombosis.
o When thrombosis affects the hepatic veins, it may produce acute hepatomegaly and ascites, i.e., a
full-fledged Budd-Chiari syndrome, which, in the absence of liver disease, ought to raise the
suspicion of PNH.
 The natural history of PNH can extend over decades.
• Without treatment, the median survival is estimated to be about 8–10 years;
• in the past, the most common cause of death has been
§ venous thrombosis,
§ followed by infection secondary to severe neutropenia & hemorrhage becoz of severe thrombocytopenia.
• Rarely (estimated 1–2% of all cases), PNH may terminate in acute myeloid leukemia.
• On the other hand, full spontaneous recovery from PNH has been documented, albeit rarely.

43. PNH lab findings
• most consistent blood finding is anemia, which may range from mild to moderate to very severe.
o usually normomacrocytic, with unremarkable red cell morphology.
o If the MCV is high, it is usually largely accounted for by reticulocytosis
o may become microcytic if the patient is allowed to become iron deficient as a result of chronic urinary blood
loss through hemoglobinuria.
• Unconjugated bilirubin is mildly or moderately elevated;
• LDH is typically markedly elevated (values in the thousands are common);
• haptoglobin is usually undetectable.
• Hemoglobinuria may be overt in a random urine sample;
 obtain serial urine samples, hemoglobinuria can vary dramatically from day to day and even from
hour to hour.
• The bone marrow is
o usually cellular, with marked to massive erythroid hyperplasia, often with mild to moderate dyserythropoietic
features (not to be confused with myelodysplastic syndrome).
o At some stage of the disease, the marrow may become hypocellular or even frankly aplastic.

44. Diagnosis of PNH
 definitive diagnosis of PNH
 must be based on the demonstration that a substantial proportion of the patient’s red
cells have an increased susceptibility to complement (C),
due to the deficiency on their surface of proteins (particularly CD59 and CD55) that
normally protect the red cells from activated C.
 The sucrose hemolysis test is unreliable; in contrast, the acidified serum (Ham) test is
highly reliable but is carried out only in a few labs.
 The gold standard today is flow cytometry, which can be carried out on granulocytes
as well as on red cells.
 A bimodal distribution of cells, with a discrete population that is CD59 and CD55
negative, is diagnostic of PNH.

45. PNH pathophysiology
 Hemolysis is mainly intravascular and is due to an intrinsic abnormality of the red cell,
 which makes it exquisitely sensitive to activated Compliment,
 it is activated through
• the alternative pathway or
§ mainly responsible for chronic hemolysis in PNH;
• through an antigen-antibody reaction.
§ explains why the hemolysis can be dramatically exacerbated in the course of a viral or bacterial infection.
 Hypersusceptibility to C is due to deficiency of several protective membrane proteins,
o of which CD59 is the most important, because it hinders the insertion into the membrane of C9
polymers.
o deficiency of these proteins is due to the shortage of a unique glycolipid molecule, GPI,
- which, through a peptide bond, anchors these proteins to the surface membrane of cells.
o shortage of GPI is due in turn to a mutation in an X-linked gene,
called PIG-A, required for an early step in GPI biosynthesis.
 Thrombosis is one of the most immediately life-threatening complications of PNH and
o yet one of the least understood in its pathogenesis.
o It could be that deficiency of CD59 on the PNH platelet causes inappropriate platelet activation;
o however, other mechanisms are possible.

46. PNH treatment
 PNH may be a lifelong condition, and
 most patients receive supportive treatment only,
 including transfusion of filtered red cells whenever necessary,
 which, for some patients, means quite frequently.
 Folic acid supplements (at least 3 mg/d) are mandatory;
 serum iron should be checked periodically, and iron supplements should be administered as appropriate.
 Long-term glucocorticoids are not indicated because there is no evidence that they have any effect on chronic hemolysis;
 A major advance in the management of PNH has been the development of a humanized monoclonal
antibody, eculizumab, which binds to the complement component C5 near the site that, when cleaved, will
trigger the distal part of the complement cascade leading to the formation of membrane attack complex (MAC).
 The only form of treatment that currently can provide a definitive cure for PNH is allogeneic BMT.
 For patients with the PNH-AA syndrome,
 immunosuppressive treatment with antithymocyte globulin and cyclosporine A may be indicated
 Any patient who has had venous thrombosis should be on regular anticoagulant prophylaxis activator may
be indicated.

47. ECULIZUMAB and PNH
 eculizumab proved effective and was licensed in 2007.
 A major advance in the management of PNH has been the development of a humanized monoclonal
antibody, eculizumab,
 which binds to the complement component C5 near the site that, when cleaved, will trigger the distal
part of the complement cascade leading to the formation of membrane attack complex (MAC).
 Eculizumab, by abrogating complement-dependent intravascular hemolysis,
• significantly improves the quality of life of PNH patients.
• need for blood transfusion would also be abrogated; indeed, this is the case in about one-half of patients, in
many of whom there is also a rise in hemoglobin levels.
• In the remaining patients, however, the anemia remains sufficiently severe to require blood transfusion.
once the distal complement pathway is blocked, red cells no longer destroyed by the MAC become opsonized by
complement (C3) fragments and undergo extravascular hemolysis.
Based on its half-life, eculizumab must be administered intravenously every 14 days.
the availability of eculizumab has decreased significantly the proportion of patients receiving BMT

48. Extracorpuscular acquired hemolytic anemia

50. Mechanical destruction
 Although red cells are characterized by the remarkable deformability that enables them to squeeze
through capillaries narrower than themselves for thousands of times in their lifetime,
 there are at least
 two situations in which they succumb to shear, if not to wear and tear;
 the result is intravascular hemolysis, resulting in hemoglobinuria.
 One situation is
 acute and self-inflicted, march hemoglobinuria.
 A similar syndrome may develop after prolonged barefoot ritual dancing or intense playing of bongo drums.
 The other situation is
 chronic and iatrogenic (it has been called microangiopathic hemolytic anemia).
 It takes place in patients with prosthetic heart valves, especially when paraprosthetic regurgitation is
present. If the hemolysis consequent on mechanical trauma to the red cells is mild, and if the supply of iron is
adequate, the loss may be largely compensated;
 if more than mild anemia develops, reintervention to correct regurgitation may be required

51. infections
• most frequent infectious cause of HA, in endemic areas, is malaria .
• In other parts of the world,
o the most frequent direct cause is probably Shiga toxin–producing E. coli O157:H7,
 now recognized as the main etiologic agent of HUS, which is more common in children than
in adults.
 Life-threatening intravascular hemolysis
due to a toxin with lecithinase activity, occurs with Clostridium perfringens sepsis,
• particularly following open wounds,
• septic abortion, or
• as a disastrous accident due to a contaminated blood unit.
• Rarely, and if at all in children, HA is seen with sepsis or endocarditis from a variety of organisms.
• In addition, bacterial and viral infections can cause HA by indirect mechanisms

52. Immune hemolytic anemia
 These can arise through at least two distinct mechanisms.
 (1) There is a true autoantibody directed against a red cell antigen,
 i.e., a molecule present on the surface of red cells.
 (2) When an antibody directed against a certain molecule (e.g., a drug) reacts with that molecule,
red cells may get caught in the reaction, whereby they are damaged or destroyed.
 Because the antibodies involved differ in optimum reactivity temperatures,
they are classified in the time-honored categories of
“cold” and “warm”.
 Autoantibody-mediated HAs may be seen in
• isolation (when they are called idiopathic) or
• as part of a systemic autoimmune disorder such as systemic lupus erythematosus.

53. IMMUNE HEMOLYTIC ANEMIAS
classification

54. AIHA
 Once a red cell is coated by an autoantibody, it will be destroyed by one or more mechanisms.
1. In most cases, the Fc portion of the antibody will be recognized by the Fc receptor of macrophages, and
this will trigger erythrophagocytosis.
• Thus, destruction of red cells will take place wherever macrophages are abundant, i.e., in the spleen, liver, or
bone marrow; this is called extravascular hemolysis.
• Because of the special anatomy of the spleen, this organ is particularly efficient in trapping antibody-coated red
cells, and often this is the predominant site of red cell destruction.
2. In some cases, the nature of the antibody is such (usually an IgM antibody) that the antigen-antibody
complex on the surface of red cells is able to activate complement (C);
• as a result, a large amount of membrane attack complex will form, and
• the red cells may be destroyed directly; this is known as intravascular hemolysis.

55. Clinical features of AIHA
• AIHA is a serious condition;
• without appropriate treatment, it may have a mortality of approximately 10%.
• The onset is often abrupt and can be dramatic.
• The hemoglobin level can drop, within days, to as low as 4 g/dL;
• the massive red cell removal will produce jaundice; and
• sometimes the spleen is enlarged.
 When this triad is present, the suspicion of AIHA must be high.
• 1. When AIHA develops in a person who is already known to have, for instance,
 systemic lupus or chronic lymphocytic leukemia, we call it a complication;
• 2. conversely, when AIHA presents on its own,
 it may be a pointer to an underlying condition that we ought to seek out.
 In some cases,
 AIHA can be associated, on first presentation or subsequently, with autoimmune thrombocytopenia
 (Evans’ syndrome).

56. Treatment of AIHA
 Severe AIHA is a medical emergency
• treatment almost invariably includes transfusion of red cells.
• pose a special problem because, if the antibody involved is nonspecific, all of the blood
units cross-matched will be incompatible.
• In these cases, it is often correct, paradoxically, to transfuse incompatible blood, that the
transfused red cells will be destroyed no less but no more than the patient’s own red cells,
but in the meantime, the patient stays alive.
• situation like this requires understanding between the clinical unit treating the patient and
the blood transfusion/serology lab.
• Whenever the anemia is not immediately life-threatening, blood transfusion should
be withheld (because compatibility problems may increase with each unit of blood
transfused)

57. Medical treatment of AIHA
• medical treatment started immediately with
o prednisone (1 mg/kg per day), which will produce a remission promptly in at least one-half of
patients.
o Rituximab (anti-CD20) was regarded as second-line treatment, but it is increasingly likely that a
relatively low dose (100 mg/wk × 4) of rituximab together with prednisone will become a first-line
standard. It is especially encouraging that this approach seems to reduce the rate of relapse, a
common occurrence in AIHA.
o relapse or are refractory to medical treatment, one may have to consider splenectomy, which,
although it does not cure the disease, can produce significant benefit by removing a major site of
hemolysis, thus improving the anemia and/or reducing the need for other therapies (e.g., the dose of
prednisone).
o Since the introduction of rituximab, azathioprine, cyclophosphamide, cyclosporine, and intravenous
immunoglobulin have become second- or third-line agents.
o In very rare severe refractory cases, either autologous or allogeneic hematopoietic stem cell
transplantation may have to be considered

58. PCH
 PCH is a rather rare form of AIHA occurring
• mostly in children,
• usually triggered by a viral infection,
• self-limited, and
• characterized by the involvement of the so-called Donath-Landsteiner antibody.
•
 In vitro, this antibody has unique serologic features;
• it binds to red cells only at a low temperature (optimally at 4°C), but when the temperature is
shifted to 37°C, lysis of red cells takes place in the presence of complement.
• Consequently, in vivo there is intravascular hemolysis, resulting in hemoglobinuria.
 Clinically the differential diagnosis must include other causes of hemoglobinuria,
 but the presence of the Donath-Landsteiner antibody will prove PCH.
 Active supportive treatment,
• including blood transfusion, is needed to control the anemia;
• subsequently, recovery is the rule.

59. CAD; cold agglutinin disease
 a form of chronic AIHA that usually affects the elderly and has
special clinical and pathologic features.

 First, the term cold refers to the fact that the autoantibody involved
 reacts with red cells poorly or not at all at 37°C, whereas it reacts strongly at lower temperatures.
 So, hemolysis is more prominent the more the body is exposed to the cold.
 The antibody is usually IgM
 Second, the antibody is produced by an expanded clone of B lymphocytes, and
 sometimes its concentration in the plasma is high enough to show up as a spike in plasma protein
electrophoresis, i.e., as a monoclonal gammopathy.
 Third, because the antibody is IgM, CAD is related to Waldenström’s macroglobulinemia (WM),
 although in most cases, the other clinical features of this disease are not present.
 Thus, CAD must be regarded as a form of WM (i.e., as a low-grade mature B cell lymphoma) that manifests
at an earlier stage precisely because the unique biologic properties of the IgM that it produces give the
clinical picture of chronic HA.

60. Treatment of CAD
• In mild forms of CAD,
 avoidance of exposure to cold may be all that is needed to enable the patient to have a
reasonably comfortable quality of life;
• but in more severe forms, the management of CAD is not easy.
§ Blood transfusion is not very effective because donor red cells are I positive and will be
rapidly removed.
§ Immunosuppressive/cytotoxic treatment with azathioprine or cyclophosphamide can reduce
the antibody titer, but clinical efficacy is limited, and in view of the chronic nature of the
disease, the side effects may prove unacceptable.
§ Unlike in AIHA, prednisone and splenectomy are ineffective.
§ Plasma exchange will remove antibody and is, therefore, in theory, a rational approach, but it
is laborious and must be carried out at frequent intervals if it is to be beneficial.
§ The management of CAD has changed significantly with the advent of rituximab; although its
impact on CAD is not as great as on AIHA, up to 60% of patients respond, and remissions
may be more durable with a rituximab-fludarabine combination.

61. Toxic agents and drugs
 Number of chemicals with oxidative potential, whether medicinal or not, can cause hemolysis even in
people who are not G6PD deficient
 Examples are
• hyperbaric oxygen (or 100% oxygen),
• nitrates,
• chlorates,
• methylene blue,
• dapsone,
• cisplatin, and
• numerous aromatic (cyclic) compounds.
 Other chemicals may be hemolytic through nonoxidative, largely unknown mechanisms;
 examples include
• arsine,
• stibine,
• copper, and
• lead.

64. REFERENCES
 HARRISON 19TH EDITION
 PROGRESS IN MEDICINE 2017

65. Thank you