CHAPTER 27: HEMOGLOBINOPATHIES (STRUCTURAL DEFECTS IN HEMOGLOBIN) Flashcards
(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
d. Decreased production of a globin chain
(2) The substitution of valine for glutamic acid at position 6 of the β 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 (Fe3+) state
b. Polymerizes to form tactoid crystals
(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
c. Higher levels of Hb F are present
(4) Megaloblastic episodes in SCD can be prevented by prophylactic administration of:
a. Iron
b. Folic acid
c. Steroids
d. Erythropoietin
b. Folic acid
(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
d. Hemoglobin electrophoresis at acid pH
(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 β chains
b. Substitution of lysine for glutamic acid at position 6 of the β chain
c. Substitution of tyrosine for the proximal histidine in the β chain
d. Double amino acid substitution in the β chain
b. Substitution of lysine for glutamic acid at position 6 of the β chain
(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.
a. The patient has Hb M.
(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%
b. 25%
(9) Painful crises in patients with SCD occur as a result of:
a. Splenic sequestration
b. Aplasia
c. Vasoocclusion
d. Anemia
c. Vasoocclusion
(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
a. Are insoluble in reduced, deoxygenated form
(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
b. Homozygous/disease
(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
d. Sub-Saharan Africa
(13) Which hemoglobinopathy is more common in Southeast Asian patients?
a. Hb S
b. Hb C
c. Hb O
d. Hb E
d. Hb E
(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
b. Hb SG
(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
c. Hb CO
