Deck 27: Thalassemias

Question 1

What is the basic hemoglobin defect in the thalassemias?

A) One of the globin chains has an amino acid substitution.
B) A structurally normal globin chain is absent or produced at lower levels.
C) Heme is produced at a lower concentration.
D) Iron is not incorporated into the protoporphyrin ring to form heme.

Answer 1

A structurally normal globin chain is absent or produced at lower levels.

Question 2

Which of the following is the normal approximate percentage of hemoglobins in adults? $\alpha$ ₂ $\beta$ ₂ $\alpha$ ₂ $\delta$ ₂ $\alpha$ ₂ $\gamma$ ₂

A) 2% 2% 96%
B) 2% 96% 2%
C) 96% 2% 2%
D) 40% 20% 40%

Answer 2

96% 2% 2%

Question 3

Patients who are heterozygous for Hb Lepore have a clinical course:

A) That is completely benign
B) Similar to that of $\beta$ -thalassemia minor
C) Similar to that of $\alpha$ -thalassemia minor (one gene deletion)
D) Similar to that of $\beta$ -thalassemia major

Answer 3

Similar to that of $\beta$ -thalassemia minor

Question 4

Homozygous $\alpha$ -thalassemia (--/--) has what clinical outcome?

A) Incompatible with life
B) Severe anemia
C) Mild anemia
D) No anemia

Question 5

Which of the following would be an unexpected finding in homozygous $\beta$ ⁰-thalassemia?

A) Decreased reticulocyte production index
B) Normal Hb F
C) Bone marrow erythroid hyperplasia
D) Severe anemia

Question 6

A patient has 30% Hb F. Which of the following can be eliminated?

A) Four missing genes for $\alpha$ chain production
B) Heterozygous hereditary persistence of Hb F
C) Thalassemia intermedia
D) The patient is a normal 1-month-old infant

Question 7

Iron overload in severe $\beta$ -thalassemia ( $\beta$ -thalassemia major) patients is primarily a consequence of:

A) An increased rate of absorption of iron because of the severe anemia
B) A decreased need for iron because fewer RBCs are made
C) Accumulation of iron from massive RBC transfusion therapy
D) Decreased rate of use of iron because smaller RBCs are made

Question 8

Which of the following is useful in helping to distinguish mild asymptomatic iron deficiency from thalassemia trait?

A) Low MCV with relatively high red blood count
B) Mild anemia
C) Increased osmotic fragility
D) Increased ferritin

Question 9

A patient with $\beta$ ⁺-thalassemia has, from that gene locus:

A) Variable but decreased $\beta$ globin chain synthesis
B) No $\beta$ globin chain synthesis
C) Variable but decreased $\gamma$ chain synthesis
D) No gamma chain synthesis

Question 10

Which of the following is the primary mechanism for anemia in the thalassemias?

A) An imbalance in the rate of globin chain synthesis
B) Impaired iron incorporation into the protoporphyrin ring
C) Erythroid hypoplasia in the bone marrow
D) Abnormal amino acid structure of a globin chain

Question 11

Which of the following is or are expected findings in $\beta$ -thalassemia minor?

A) Basophilic stippling
B) Normal levels of Hb F and Hb A₂
C) Normocytic normochromic red cells
D) Hemoglobin levels in the 4- to 6-g/dL range

Question 12

Why are infants with $\beta$ -thalassemia major not ill until approximately 6 months of age?

A) Infants are protected by their high concentration of Hb F.
B) Infants have less need for hemoglobin because of their small body size.
C) Infants have less need for hemoglobin because of their smaller lung capacity.
D) Infants have a high red count and thus higher hemoglobin from a higher than normal concentration of erythropoietin.

Question 13

Hemoglobin E (Hb E) is primarily found in individuals of which ethnic origin?

A) Mediterranean
B) African
C) Southeast Asian
D) Northern European

Question 14

Hb Barts is composed of:

A) ( $\alpha$ ₄)
B) ( $\gamma$ ₄)
C) ( $\beta$ ₄)
D) (₄)

Question 15

Which of the following is least useful in diagnosing and differentiating the thalassemias from each other?

A) Complete blood count (CBC) results
B) Hemoglobin electrophoresis
C) Osmotic fragility
D) Clinical findings

Question 16

What finding is present in all types of $\alpha$ -thalassemias?

A) Hemoglobin H (Hb H) inclusions seen with Brilliant cresyl blue
B) Anemia
C) Microcytic hypochromic red cells
D) Barts hemoglobin present at birth

Question 17

Which of the following is true of patients with Hb H disease?

A) Have a severe anemia
B) Have three missing genes for $\alpha$ chain production
C) Have excess unpaired $\beta$ chains present
D) Are of Northern European ethnicity

Question 18

All of the following can distinguish $\beta$ -thalassemia minor from major except:

A) Clinical findings
B) Hemoglobin concentration
C) Presence of microcytosis, hypochromasia, and target cells
D) Presence of Hb A

Question 19

Which of the following can help distinguish the combination Hemoglobin S (Hb S) $\beta$ ⁰-thalassemia from sickle cell anemia?

A) Hematocrit
B) Hemoglobin electrophoresis
C) Ethnic background
D) Mean cell volume (MCV)

Question 20

Which of the following is true regarding the clinical features of thalassemias?

A) Are mild conditions rarely requiring treatment
B) Are serious conditions requiring frequent blood transfusions
C) Have abnormal red cells but little clinical implications for patients
D) Vary from benign forms to those incompatible with life

Question 21

Hb A₂ and Hb F can be quantified by:

A) Performing a Brilliant cresyl blue stain and counting the number of positive cells
B) Performing high-performance liquid chromatography
C) Performing cellulose acetate hemoglobin electrophoresis
D) Performing citrate agar hemoglobin electrophoresis