Hemoglobinopathies (Structural Defects in Hemoglobin)

Question 1

1. A qualitative abnormality in hemoglobin may involve all of
   the following except:
   a. Replacement of one or more amino acids in a globin
   chain
   b. Addition of one or more amino acids in a globin chain
   c. Deletion of one or more amino acids in a globin chain
   d. Decreased production of a globin chain

Answer 1

d. Decreased production of a globin chain

Question 2

2. The substitution of valine for glutamic acid at position 6 of
   the b chain of hemoglobin results in hemoglobin that:
   a. Is unstable and precipitates as Heinz bodies
   b. Polymerizes to form tactoid crystals
   c. Crystallizes in a hexagonal shape
   d. Contains iron in the ferric (Fe31) state

Answer 2

b. Polymerizes to form tactoid crystals

Question 3

3. Patients with SCD usually do not exhibit symptoms until
   6 months of age because:
   a. The mother’s blood has a protective effect
   b. Hemoglobin levels are higher in infants at birth
   c. Higher levels of Hb F are present
   d. The immune system is not fully developed

Answer 3

c. Higher levels of Hb F are present

Question 4

4. Megaloblastic episodes in SCD can be prevented by prophylactic administration of:
   a. Iron
   b. Folic acid
   c. Steroids
   d. Erythropoietin

Answer 4

b. Folic acid

Question 5

5. Which of the following is the most definitive test for Hb S?
   a. Hemoglobin solubility test
   b. Hemoglobin electrophoresis at alkaline pH
   c. Osmotic fragility test
   d. Hemoglobin electrophoresis at acid pH

Answer 5

d. Hemoglobin electrophoresis at acid pH

Question 6

6. A patient presents with mild normochromic, normocytic
   anemia. On the peripheral blood film, there are a few target cells, rare nucleated RBCs, and hexagonal crystals
   within and lying outside of the RBCs. Which abnormality
   in the hemoglobin molecule is most likely?
   a. Decreased production of b chains
   b. Substitution of lysine for glutamic acid at position 6 of
   the b chain
   c. Substitution of tyrosine for the proximal histidine in
   the b chain
   d. Double amino acid substitution in the b chain

Answer 6

b. Substitution of lysine for glutamic acid at position 6 of
the b chain

Question 7

7. A well-mixed specimen obtained for a CBC has a brown
   color. The patient is being treated with a sulfonamide for a
   bladder infection. Which of the following could explain
   the brown color?
   a. The patient has Hb M.
   b. The patient is a compound heterozygote for Hb S and
   thalassemia.
   c. The incorrect anticoagulant was used.
   d. Levels of Hb F are high.

Answer 7

a. The patient has Hb M.

Question 8

8. Through routine screening, prospective parents discover
   that they are both heterozygous for Hb S. What percentage
   of their children potentially could have sickle cell anemia
   (Hb SS)?
   a. 0%
   b. 25%
   c. 50%
   d. 100%

Answer 8

b. 25%

Question 9

9. Painful crises in patients with SCD occur as a result of:
   a. Splenic sequestration
   b. Aplasia
   c. Vasoocclusion
   d. Anemia

Answer 9

c. Vasoocclusion

Question 10

10. The screening test for Hb S that uses a reducing agent, such
    as sodium dithionite, is based on the fact that hemoglobins that sickle:
    a. Are insoluble in reduced, deoxygenated form
    b. Form methemoglobin more readily and cause a color
    change
    c. Are unstable and precipitate as Heinz bodies
    d. Oxidize quickly and cause turbidity

Answer 10

a. Are insoluble in reduced, deoxygenated form

Question 11

11. DNA analysis documents a patient has inherited the sickle
    mutation in both b-globin genes. The two terms that best
    describe this genotype are:
    a. Homozygous/trait
    b. Homozygous/disease
    c. Heterozygous/trait
    d. Heterozygous/disease

Answer 11

b. Homozygous/disease

Question 12

12. In which of the following geographic areas is Hb S most
    prevalent?
    a. India
    b. South Africa
    c. United States
    d. Sub-Saharan Africa

Answer 12

d. Sub-Saharan Africa

Question 13

13. Which hemoglobinopathy is more common in Southeast
    Asian patients?
    a. Hb S
    b. Hb C
    c. Hb O
    d. Hb E

Answer 13

d. Hb E

Question 14

14. Which of the following Hb S compound heterozygote exhibits the mildest symptoms?
    a. Hb S-b-Thal
    b. Hb SG
    c. Hb S-C-Harlem
    d. Hb SC

Answer 14

b. Hb SG

Question 15

15. A 1-year-old Indian patient presents with anemia, and
    both parents claim to have an “inherited anemia” but can’t
    remember the type. The peripheral blood shows target
    cells, and the hemoglobin solubility is negative. Alkaline
    hemoglobin electrophoresis shows a single band at the
    “Hb C” position and a small band at the “Hb F” position.
    Acid hemoglobin electrophoresis shows two bands. The
    most likely diagnosis is:
    a. Hb CC
    b. Hb AC
    c. Hb CO
    d. Hb SC

Answer 15

c. Hb CO

Question 16

16. Unstable hemoglobins show all of the following findings
    EXCEPT:
    a. Globin chains precipitate intracellularly
    b. Heinz body formation
    c. Elevated reticulocyte count
    d. Only homozygotes are symptomatic

Answer 16

d. Only homozygotes are symptomatic