Practice Question Answers Anemia VII

Practice Question Answers

Anemia VII

© Jun Wang, MD, PhD

 

Abbreviations:

Hb: hemoglobin	HCT: hematocrit
MCV: Mean Corpuscular Volume	MCH: Mean Corpuscular Hemoglobin
RDW: Red Cell Distribution Width	TIBC: total iron binding capacity

 

1. A. This patient has a few conditions that may cause fatigue. However, dark urine and jaundice are commonly seen with hemolysis. Her low hemoglobin and elevated reticulocyte count and bilirubin are consistent with hemolytic anemia. Positive DAT is consistent with immune hemolytic anemia. Depression, hypothyroidism, liver disease and Prozac seldom cause hemolysis.

2. E. The peripheral blood smear reveals many spherocytes (RBCs without central pallor area). Warm auto-immune antibodies cause spherocytic changes in immune hemolytic anemia. Cold agglutinin disease is characterized by recurrent painful episodes of fingers and toes and bluish discoloration involving skin that are triggered by low temperature. It is caused by cold reacting auto-antibodies, primarily IgM. Serum M-proteins is seen in plasma neoplasms, such as multiple myeloma, etc. RBC aggregates may be seen in cold agglutinin disease and when M-protein increases. Hemoglobin abnormalities, including thalassemia, sickle cell anemia, HbC and HbE, have red cell changes, such as sickle cell, rhomboidal crystals, or target cells. Red cell cytoskeletal defects are seen in hereditary spherocytosis. But DAT should be negative for hereditary spherocytosis and hemoglobinopathies.

3. C. See discussion of question 1. This patient has no history or evidence of biliary tract obstruction, liver injury or splenic tumor.

4. F. See discussion of questions 1 and 2. G6PD deficiency is characterized by sudden onset of hemolysis triggered by oxidative stress. Hereditary spherocytosis has spherocytes. Pyruvate kinase deficiency tends to have chronic clinical course.  Paroxysmal nocturnal hemoglobinuria is characterized by dark urine started at night and cleared during the day. DAT should be negative in these condition. Cold agglutinin disease is characterized by recurrent painful episodes of fingers and toes and bluish discoloration involving skin that are triggered by low temperature. It is caused by cold reacting auto-antibodies, primarily IgM. DAT usually is positive for complement only, but not IgG.

5. A. This case is characterized by anemia, hemolysis, aggregates of RBCs at room temperature, and positive DAT with complement only. Her symptoms worsens when temperature is low. These features are consistent with cold agglutinin disease. It is caused by cold reacting auto-antibodies, primarily IgM. Complements are important in immune attack, but usually do not cause aggregates. Hemoglobin abnormalities, including thalassemia, sickle cell anemia, HbC and HbE, have red cell changes, such as sickle cell, rhomboidal crystals, or target cells. Red cell cytoskeletal defects are seen in hereditary spherocytosis. Reduced RBC NADPH is seen in G6PD deficiency. These usually do not have cold agglutinin (cold reacting antibody).

6. E. See discussion of question 1. IgG, IgA and lambda light chain may rarely be associated with cold agglutinin disease.

7. D. RBCs aggregate at body parts with lower temperature due to cold agglutinin. These aggregates may block blood flow and cause local ischemic changes. Other conditions do not specifically affects body parts with lower temperature.

8. C. Cold agglutinin disease most commonly target RBC surface antigen I or i.

9. A. See discussion of questions 4 and 5. Sickle cell anemia has sickle cells.

10. D. This case is characterized by sudden onset of symptoms during transfusion, highly suspicious for transfusion reaction. The first thing need to do is to stop transfusion. Any other investigations or management can be after transfusion is stopped.

11. B. This is a sudden onset of symptoms including fever, chills, and hypotension. His indirect bilirubin is elevated, and haptoglobin depleted, consistent with an acute hemolytic transfusion reaction. DAT is the test to confirm the presence of anti-RBC antibodies. While this patient has fever and chill, suggestive of bacterial infection, the presence of severe hemolysis shortly after transfusion started make it more likely to be acute hemolytic transfusion reaction. Enzymatic activity of G6PD is used to diagnose G6PD deficiency, an acute hemolysis triggered by oxidative stress, not blood transfusion. Eosin-5-maleimide binding assay is used to diagnose hereditary spherocytosis. Parvovirus B19 test is used to diagnose aplastic anemia associated with Parvovirus B19 infection, such as pure red cell aplasia, or aplastic crisis in sickle cell anemia. Smear for RBC parasites may detect intracellular parasites. However, these conditions are not associated with transfusion, and have past medical history of hemolysis.

12. B. Positive DAT confirmed immune hemolytic transfusion reaction. Bacterial toxin may cause hemolysis.  Sudden onset of hemolysis triggered by oxidative stress is seen in G6PD deficiency. RBC membrane instability causes hemolysis in hereditary spherocytosis. These conditions usually have negative DAT. Reduced erythropoietin production usually does not cause hemolysis.

13. A. This is a case of acute hemolytic transfusion reaction, most common caused by ABO mismatch due to clerical error.  DAT will be negative in cases of allergy, bacterial infection, G6PD deficiency and hereditary spherocytosis.

14. See discussion of questions 11 and 12.

15. C. This case is characterized by signs of hydrops fetalis. The mother is Rh- O, with an uneventful previous pregnancy. The father is Rh+ A. So the fetus is possibly Rh+ as well. This is a common clinical setting of hemolytic disease of the fetus. The mother is sensitized to fetal Rh, most likely during her first pregnancy when the fetal RBC entered maternal circulation. However, since the initial immune reaction produces IgM, that cannot pass placenta, the first fetus was not affect. When the RBCs of second fetus entered maternal blood, secondary immune reaction will produce IgG against Rh antigens, as confirmed by positive indirect Coombs test of the mother, suggesting that she has anti-RBC antibodies, most likely anti-D(Rh) of the fetal RBCs. Since IgM cannot pass placenta, the cause of hydrops fetalis is most likely anti-D IgG.

16. E. See discussion of question 15. ABO incompatibility is usually have mild clinical presentation and may affect first pregnancy.  Deletion of 4 a globin gene of fetus, as seen in Hb Bart, may cause hydrops fetalis as well. However, it is associated with absence of normal hemoglobin, not immune mediated. Fetal congenital hematopoietic stem cell defect or Parvovirus B19 infection usually do not have positive indirect Coombs test.

17. F. See discussion of question 15.

 

 

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