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Path U2 > Ch5 - 6) Normocytic anemia with predominant intravascular hemolysis > Flashcards

Ch5 - 6) Normocytic anemia with predominant intravascular hemolysis Flashcards

1
Q

What are the normocytic anemias with predominant intravascular hemolysis?

A

1) paroxysmal nocturnal hemoglobinuria (PNH) 2) G6PD deficiency 3) Immune Hemolytic anema (INH) 4) Microangiopathic hemolytic anemia 5) Malaria

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2
Q

What is paroxysmal nocturnal hemoglobinuria?

A

Acquired defect in myeloid stem cells resulting in absent glycosylphosphatidylinositol (GPI); renders cells susceptible to destruction by complement

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3
Q

What is the relationship between blood cells and complement?

A

Blood cells coexist with complement.

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4
Q

What is DAF?

A

Decay accelerating factor (DAF) is on the surface of blood cells and protects against complement-mediated damage by inhibiting C3 convertase.

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5
Q

How is DAF secured to the cell membrane?

A

By GPI (an anchoring protein)

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6
Q

What does the absence of GPI on the RBC membrane leads to?

A

absence of DAF, rendering cells susceptible to complement-mediated damage.

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7
Q

How is intravascular hemolysis related to paroxysmal nocturnal hemoglobinuria?

A

Intravascular hemolysis occurs episodically, often at night during sleep,

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8
Q

What develops in paroxysmal nocturnal hemoglobinuria?

A
  1. Mild respiratory acidosis develops with shallow breathing during sleep and activates complement.
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9
Q

In paroxysmal nocturnal hemoglobinuria what is lysed?

A

RBCs, WBCs, and platelets are lysed

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10
Q

What test is used to screen for paroxysmal nocturnal hemoglobinuria?

A

Sucrose test

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11
Q

What is a confirmatory test for paroxysmal nocturnal hemoglobinuria?

A

Acidified serum test or flow cytometry to detect the lack of CD55 (DAF) on blood cells

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12
Q

What is the main cause of death in paroxysmal nocturnal hemoglobinuria?

A

It is thrombosis of the hepatic, portal, or cerebral veins.

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13
Q

In paroxysmal nocturnal hemoglobinuria what induces thrombosis?

A

Destroyed platelets release cytoplasmic contents into circulation, inducing thrombosis.

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14
Q

In paroxysmal nocturnal hemoglobinuria what are the complications?

A

iron deficiency anemia which is due to chronic loss of hemoglobin in the urine) and acute myeloid leukemia (AML), which develops in 10% of patients.

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15
Q

What is G6PD deficiency?

A

X-linked recessive disorder resulting in reduced half-life of G6PD; renders cells susceptible to oxidative stress

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16
Q

How does G6PD deficiency lead to intravascular hemolysis?

A

decreased G6PD ? decreased NADPH ? reduced glutathione ? oxidative injury by H202 ? intravascular hemolysis

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17
Q

What is the relationship between G6PD and RBCs?

A

RBCs are normally exposed to oxidant stresses particularly H2O2.

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18
Q

What neutralizes H2O2?

A

Glutathione (an antioxidant) neutralizes H2O2, but becomes oxidized in the process.

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19
Q

What is needed to regenerate glutathione?

A

NADPH, a by-product of G6PD, is needed to regenerate reduced glutathione.

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20
Q

How many variants are there for G6PD deficiency?

A

There are two major variants; African variant and Mediterranean variant

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21
Q

What is seen with the African variant of G6PD deficiency?

A

mildly reduced half-life of G6PD leading to mild intravascular hemolysis with oxidative stress

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22
Q

What is seen in the Mediterranean variant of G6PD deficiency?

A

markedly reduced half-life of G6PD leading to marked intravascular hemolysis with oxidative stress

23
Q

Explain the carrier frequency for both variants of G6PD deficiency?

A

High carrier frequency in both populations is likely due to protective role against falciparum malaria.

24
Q

What is the relationship between G6PD deficiency and Heinz bodies?

A

Oxidative stress precipitates Hb as Heinz bodies

25
Q

What are some causes of oxidative stress?

A

infections, drugs (e.g., primaquine, sulfa drugs, and dapsone), and fava beans.

26
Q

What happens to Heinz bodies?

A

they are removed from RBCs by splenic macrophages, resulting in bite cells

27
Q

Hb precipitating as Heinz bodies leads to what?

A

Predominantly leads to intravascular hemolysis

28
Q

What does G6PD deficiency present with?

A

hemoglobinuria and back pain hours after exposure to oxidative stress

29
Q

What is used to screen G6PD deficiency?

A

Heinz preparation is used to screen for disease

30
Q

How can precipitated Hb be seen?

A

precipitated hemoglobin can only be seen with a special Heinz stain

31
Q

What is used to confirm G6PD deficiency? When is it performed?

A

enzyme studies confirm deficiency (performed weeks after hemolytic episode resolves).

32
Q

What is immune hemolytic anemia?

A

Antibody-mediated (IgG or IgM) destruction of RBCs

33
Q

In IHA what does the IgG-mediated disease usually involve?

A

extravascular hemolysis.

34
Q

In IgG mediated IHA how does spherocyte formation result?

A

IgG binds RBCs in the relatively warm temperature of the central body (warm agglutinin); membrane of antibody-coated RBC is consumed by SPLENIC macrophages, resulting in spherocytes

35
Q

What is the most common cause of IgG mediated IHA?

A

SLE

36
Q

What is IgG mediated IHA associated with?

A

SLE (most common cause), CLL, and certain drugs (classically, penicillin and cephalosporins)

37
Q

How do certain drugs relate to IgG mediated IHA?

A

Drug may attach to RBC membrane (e.g., penicillin) with subsequent binding of antibody to drug-membrane complex. 2). Drug may induce production of autoantibodies (e.g., u-methyldopa) that bind self antigens on RBCs

38
Q

What does the treatment of IgG mediated IHA involve?

A

cessation of the offending drug, steroids, IVIG, and, if necessary, splenectomy.

39
Q

What does IgM-mediared IHA disease usually involve?

A

intravascular hemolysis.

40
Q

What happens in IgM mediated IHA?

A

IgM binds RBCs and fixes complement in the relatively cold temperature of the extremities (cold agglutinin).

41
Q

What is the IgM mediated IHA associated with?

A

Mycoplasma pneumoniae and infectious mononucleosis

42
Q

What test is used to diagnose IHA?

A

Coombs test is used to diagnose IHA; testing can be direct or indirect.

43
Q

What is the Direct Coombs test?

A

confirms the presence of antibody-coated RBCs. Anti-IgG is added to patient RBCs; agglutination occurs if RBCs are already coated with antibody.

44
Q

What is the most important test for IHA?

A

Direct Coombs test

45
Q

What is the indirect Coombs test?

A

it confirms the presence of antibodies in patient serum. Anti-IgG and test RBCs are mixed with the patient serum; agglutination occurs if serum antibodies are present.

46
Q

What is microangiopathic hemolytic anemia?

A

Intravascular hemolysis that results from vascular pathology; RBCs are destroyed as they pass through the circulation.

47
Q

What occurs with chronic hemolysis?

A

Iron deficiency anemia

48
Q

Microangiopathic hemolytic anemia occurs with what?

A

Occurs with microthrombi (TTP-HUS, DIG, HELLP), prosthetic heart valves, and aortic stenosis; microthrombi produce schistocytes on blood smear

49
Q

What is malaria?

A

Infection of RBCs and liver with Plasmodium, transmitted by the female Anopheles mosquito

50
Q

How does malaria affect RBCs?

A

RBCs rupture as a part of the Plasmodium life cycle, resulting in intravascular hemolysis and cyclical fever.

51
Q

What does P falciparum present with?

A

daily fever

52
Q

What does P vivax and P ovale present as?

A

fever every other day

53
Q

What is the role of the spleen in malaria?

A

Spleen consumes some infected RBCs; results in mild extravascular hemolysis with splenomegaly

Path U2 (25 decks)

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