Hemoglobinopathies Practice Questions Flashcards
What is the best approach to an otherwise healthy, asymptomatic 12 month old female with the hemoglobin of 9.1 g/dL (MCV 58) on routine CBC screen and the presence of Hemoglobin Barts on her newborn screen?
A. Explain to the parents that the baby may have thalassemia and obtain an electrophoresis
B. Start the baby on Fe supplements and order an electrophoresis
C. Start the baby on Fe supplements, recheck in a month, and if the hemoglobin is not improved then, assume the baby has thalassemia
D. Counsel the family that the baby has a form of alpha thalassemia, and that no immediate other tests or Fe supplements are needed
D. Counsel the family that the baby has a form of alpha thalassemia, and that no immediate other tests or Fe supplements are needed
Presence of HbBarts protein at the time of newborn is enough to indicate alpha thalassemia (HbH disease). Anemia increases iron uptake from the GI tract, so any option including iron supplements would be wrong. There is no reason to repeat a test already done that was diagnostic, so no further electrophoresis (and the insurance company would refuse to pay for such worthless testing). For completeness: a person with this hemoglobin concentration would usually not have clinical signs necessitating a blood transfusion.
Which of the following neurological complications is most commonly experienced by adults with sickle cell anemia?
A. Intracranial hemorrhage
B. Cerebral infarction
C. Seizures
D. Visual changes
E. Ataxia
B. Cerebral infarction
Sickling RBC can cause infarction in any tissue including brain.
Which would NOT be an effective way to diagnose sickle cell anemia?
A. Hemoglobin electrophoresis
B. PCR exon 1 of the B-globin gene, followed by allele specific hybridization specific for normal and betaS alleles
C. Enzymatic assay for hemoglobin activity
D. PCR exon 1 of the B-globin gene, followed by restriction digest with MstII
E. Restriction digest of genomic DNA with MstII, followed by Southern blot, using a B-globin gene product as probe
C. Enzymatic assay for hemoglobin activity
HbS does have Hb activity (taking up and releasing oxygen), so that method (C) would be ineffective. And yes, this question is not quite NBME style.
In the following table, match each protein name with the components of that protein
α2β2 α2γ2 α2δ2 α2βs2 γ4 β4
HbA
HbA2
HbF
HbH
HbBarts
HbSS
HbA: α2β2
HbA2: α2δ2
HbF: α2γ2
HbH: β4
HbBarts: γ4
HbSS: α2βs2
This is obviously not in exam format, but it underlines that some relationships just must be memorized. Additionally, this question also stresses the fact that there is a protein called HbH and one called HbBarts – these designations are not only used for a disease. The correctly filled out table is shown below.
Hemoglobin C and E are two different variant hemoglobin subunits. They are variants of which and which hemoglobin forms, respectively:
A. alpha, beta
B. beta, alpha
C. gamma, alpha
D. beta, gamma
E. beta, beta
F. alpha, alpha
G. gamma, gamma
E. beta, beta
Both HbC and HbE are results of point mutations in the beta-Hb chain
After an upper respiratory tract infection, a 10-year-old girl with sickle cell disease suddenly falls very ill. A blood test shows a hemoglobin concentration of 4 g/dL. The most likely problem is:
A. Lack of erythropoietin
B. Excessive formation of fibrin clots caused by excessive sickling
C. Acute iron deficiency
D. Trapping of erythrocytes in the spleen
E. Internal bleeding
D. Trapping of erythrocytes in the spleen
Infection may lower the oxygen content of peripheral blood and thereby induce increased sickling. Those sickled cells then can become trapped in the spleen.
A cystic fibrosis mutation screen of an affected child reveals that he carries the Delta F508 mutation on one chromosome and the G551D mutation on the other chromosome. Which term describes this situation?
A. Locus heterogeneity
B. Compound heterozygosity
C. Locus heterogeneity
D. Lyonization
E. Pleiotropy
B.Compound heterozygosity
This is an example of compound heterozygote and shows that designation is not exclusive to hemoglobin diseases.
Hemoglobin S can be separated from normal hemoglobin A by electrophoresis on paper or cellulose acetate foil. The best explanation for why this is possible is because hemoglobin S:
A. Is more hydrophilic than hemoglobin A
B. Is more hydrophobic than hemoglobin A
C. Has a different number of electrical charges than hemoglobin A
D. Has a more compact shape than hemoglobin A
E. Has a different molecular weight than hemoglobin A
C. Has a different number of electrical charges than hemoglobin A
A girl had developed repeated attacks of pneumonia almost immediately after birth. A blood test taken 3 weeks after birth showed a blood hemoglobin concentration of 4.5% (normal at that age: 15-19%). This could possibly be a serious case of:
A. Sickle cell disease or α-thalassemia but not β-thalassemia
B. α-thalassemia but not sickle cell disease or β-thalassemia
C. Sickle cell disease or β-thalassemia but not α-thalassemia
D. Sickle cell disease but not α-thalassemia or β-thalassemia
E. α-thalassemia or β-thalassemia but not sickle cell disease
B. α-thalassemia but not sickle cell disease or β-thalassemia
This question is all about the switch in expression and which effects that has on when the earliest time each disease can be causing symptoms.
