HEMA LEC - Hemolytic Anemias due to Extrinsic/Immune defects

Question 1

All cause a normocytic/normochromic anemia due to defects extrinsic to the RBC. All are acquired disorders that cause accelerated destruction with reticulocytosis.

Answer 1

Hemolytic Anemias due to Extrinsic/Immune defects”

Question 2

a. RBC’s are coated with IgG and/or complement. Macrophages may phagocytize these RBC’s, or they may remove the antibody or complement from the RBC’s surface, causing membrane loss and spherocytes.

Answer 2

Warm autoimmune haemolytic anemia (WAIHA)

Question 3

b. 60% of cases are idiopathic; other cases are secondary to diseases that alter the immune response (e.g., chronic lymphocytic leukemia, lymphoma); can also be drug induced.

Answer 3

Warm autoimmune haemolytic anemia (WAIHA)

Question 4

c. Laboratory: Spherocytes, MCHC may be > 37g/dL, increased osmotic fragility, biliburin, reticulocyte count, occasional RBC’s present; positive direct antiglobulin test (DAT) helpful in differentiating from hereditary spherocytosis.

Answer 4

Warm autoimmune haemolytic anemia (WAIHA)

Question 5

RBC’s are coated with IgM and complement at temperatures below 37oC. RBC’s are lysed by complement or phagocytised by macrophages. Antibody is usually anti-I but can be anti-i.

Answer 5

Cold autoimmune haemolytic anemia (CAIHA or cold hemagglutinin disease)

Question 6

Can be idiopathic, or secondary to Mycoplasma pneumonia, lymphoma, or infectious mononucleosis.

Answer 6

Cold autoimmune haemolytic anemia (CAIHA or cold hemagglutinin disease)

Question 7

Laboratory: Seasonal symptoms; RBC clumping can be seen both macroscopically and microscopically; MCHC > 37 g/dL; increased bilirubin, reticulocyte count; positive DAT detects complement-coated RBC’s.

Answer 7

Cold autoimmune haemolytic anemia (CAIHA or cold hemagglutinin disease)

Question 8

If antibody titer is high enough, sample must be warmed to 37oC to obtain accurate RBC and indices results

Answer 8

Cold autoimmune haemolytic anemia (CAIHA or cold hemagglutinin disease)

Question 9

a. An IgG biphasic Donath- Landsteiner antibody with P specificity fixes complement to RBC’s in the cold (less than 20oC); the complement-coated RBC’s lyse when warmed to 37oC.

Answer 9

Paroxysmal cold hemoglobinuria (PCH)

Question 10

b. Can be idiopathic, or secondary to viral infections (e.g. measles, mumps) and non-Hodgkin lymphoma.

Answer 10

Paroxysmal cold hemoglobinuria (PCH)

Question 11

c. Laboratory: Variable anemia following haemolytic process; increased bilirubin and plasma hemoglobin, decreased haptoglobin; DAT may be positive; Donath-Landsteiner test positive.

Answer 11

Paroxysmal cold hemoglobinuria (PCH)

Question 12

a. Recipient has antibodies to antigens on donor RBC’s; donor cells are destroyed.

Answer 12

Hemolytic transfusion reaction

Question 13

b. ABO incompatibility causes an immediate reaction with
massive intravascular hemolysis that is complement
induced.

Answer 13

Hemolytic transfusion reaction

Question 14

c.Laboratory: Positive DAT, increased plasma hemoglobin

Answer 14

Hemolytic transfusion reaction

Question 15

1. ) Usually IgM antibodies

2. ) Can trigger DIC due to release of tissue factor from the lysed RBC’s

Answer 15

Hemolytic transfusion reaction

Question 16

3. ) Exchange transfusions in utero or shortly after birth.

4. ) No longer a common problem with us of Rh immunoglobulin (RhoGam)

Answer 16

HDN due to Rh incompatibility (erythroblastosis fetalis)

Question 17

1. ) Rh negative woman is exposed to Rh antigen from fetus and forms IgG antibody; this antibody will cross the placenta and destroy RBC’s of the next fetus that is Rh positive.
2. ) Laboratory: Severe anemia, nRBC’s, positive DAT; very high bilirubin levels cause kernicterus leading to brain damage.

Answer 17

HDN due to Rh incompatibility (erythroblastosis fetalis)

Question 18

1. ) Group O woman develops IgG antibody that crosses the placenta and coats fetal RBC’s when fetus is group A or B. The coated RBC’s are phagocytized.
2. ) Laboratory: Mild or no anemia, few spherocytes, weakly positive DAT, slightly increased bilirubin.

Answer 18

HDN due to ABO Incompatibility