Practice questions Answers Anemia II

Practice Question Answers

Anemia II

© 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. C. This patient has anemia and recurrent painful episodes. The presence of sickle cells in peripheral blood smear is consistent with sickle cell disease. Hemoglobin electrophoresis is very helpful in diagnosing hemoglobin abnormalities, including thalassemia, sickle cell anemia, HbC and HbE. Bone marrow biopsy is useful in specific diagnosis of many anemia, especially hematopoietic stem cell abnormalities, such as aplastic anemia and myeloid neoplasms. Chromosomal breakage tests and molecular tests for FANC gene mutations are used to diagnose Fanconi anemia. Osmotic fragility test is used to diagnose hereditary spherocytosis. Serum ferritin is useful in diagnosing iron metabolism abnormalities, such as iron deficiency anemia, sideroblastic anemia and anemia of chronic disease.

2. A. The early presence of symptoms and large amounts of sickle cells in peripheral blood smear is most consistent with HbSS, when HbS is the predominant form of hemoglobin, since both beta gene harbor mutations. Equally increased HbC and HbS is seen HbC disease, characterized by presence of rhomboidal crystals. Markedly elevated HbF is seen in new born or beta thalassemia major. Equal amounts of HbA and HbC is seen in patient with heterozygous HbC mutation. Slightly increased HbF can be seen in Beta thalassemia trait. Predominantly HbA with small amounts of HbA2 and HbF is seen in normal populations.

3. E. Sickling in sickle cell anemia is caused by polymerization of hemoglobin when deoxygenated, commonly triggered by hypoxia.  

4. E. Sickle cell anemia is caused by glutamate to valine substitution at codon 6 of both beta globin. Deletion of 2 alpha chain is seen in alpha thalassemia trait. Deletion of 1 beta globin can be seen in beta thalassemia minor or intermedia. Glutamate to lysine substitution at codon 6 of 1 beta globin is seen heterozygous HbC. Glutamate to lysine substitution at codon 26 of 1 beta globin is seen in heterozygous HbE.

5. D. See discussion of question 1. Alpha thalassemia trait usually do not have anemia. Beta thalassemia major tend to have target cells. HbC disease is characterized by presence of rhomboidal crystals.  Sickle cell trait has less severe clinical course. 

6. D. Sickling of RBCs in sickle cell anemia causes membrane injuries. The subsequent calcium influx results in cross-linking of membrane proteins, and further membrane damages cause hemolysis, resulting in elevation of bilirubin. Auto-immune hemolysis is seen in autoimmune hemolytic anemia. This patient does not have any evidence of liver disease. Oxidative stress causes hemolysis in patients with G6PD deficiency. Surface complement activity is associated with autoimmune hemolytic anemia and paroxysmal nocturnal hemoglobinuria.

7. C. See discussion of question 1

8. E. See discussion of question 4.

9. D. This case is characterized by severe painful episode in a patient with sickle cell anemia, most likely a pain crisis. RBCs and WBCs tend to be more adhesive in sickle cell anemia patients and are more likely to form aggregates resulting in vascular occlusion and ischemic injuries to affected tissue. While acute hemolysis is possible due to presence of jaundice, elevated reticulocytes and LDH, the background condition of sickle cell anemia and history of similar episodes are more supportive of a pain crisis. Similarly, bacterial infection, platelet thrombosis and trauma are less likely in this patient, due to lack of proper history and more supportive clinical evidences.

10. D. see discussion of question 9. Acute chest syndrome is a defined by new ratio density in patient with fever and respiratory symptoms. Aplastic crisis has reduced reticulocytes. Sequestration crisis is characterized by rapid enlargement of spleen, and hypovolemia. It is caused by capture of RBCs in spleen without evidence of massive hemolysis, as evidenced by markedly elevated bilirubin and LDH. Hemolytic crisis usually occurs together with pain crisis, and has markedly elevated bilirubin and LDH, as well as rapidly and markedly decreased RBC count and Hb levels.

11. E. See discussion of question 10.

12. A. See discussion of question 2.

13. A. See discussion of question 10.

14. E. This case is characterized by presence of sickle cells but has much mild clinical history. The presence of around 40% HbS and absence of other abnormal hemoglobin are consistent with sickle cell trait. See discussion of question 2 as well. Acute glomerulonephritis and diabetic nephropathy have proper clinical history, and usually do not have sickle cells, unless they also carry sickle cell mutation.

15. C. The most common cause of hematuria in sickle cell trait is kidney papillary necrosis. Other options do not have supportive evidence in clinical history.

16. D. This case is characterized by anemia and presence of rhomboidal crystals, suggestive of HbC disease. Hemoglobin electrophoresis is very helpful in diagnosing hemoglobin abnormalities, including thalassemia, sickle cell anemia, HbC and HbE. Chromosomal breakage tests and molecular tests for FANC gene mutations are used to diagnose Fanconi anemia. Eosin-5-maleimide (EMA) binding assay and osmotic fragility test are used to diagnose hereditary spherocytosis. Enzymatic activity of G6PD is used to diagnose G6PD deficiency.

17. B. Hemoglobin composed of predominantly HbC is consistent with homozygous HbC disease, caused by glutamate to lysine substitution at codon 6 of both beta globin genes. Deletion of 3 alpha globin is seen in HbH disease. Also see discussion of question 4. 

18. B. See discussion of question 17. Hemoglobin Bart disease is caused by deletion of 4 alpha globins and patients commonly died in utero.  Thalassemia beta major is caused by markedly reduced beta chain synthesis. Both disorders are transfusion dependent. Also see discussion of questions 1 and 5.

19. B. This case is characterized by anemia, elevated reticulocyte count, and presence of hemolysis. Peripheral blood smear reveals rhomboidal crystals and sickle cells, consistent with a HbSC. Also see discussion of 2.

20. B. See discussion of question 4.

21. C. See discussion of question 19.

 

 

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