A 5-year-old boy is brought to the office by his parents to establish medical care. The family recently immigrated to the United States from Nigeria. Both parents have sickle cell trait, and the patient was diagnosed with homozygous sickle cell disease (HbSS) at the age of 6 months. He has had several prior vasoocclusive crises and takes folic acid and hydroxyurea. Physical examination shows no abnormalities. Hemoglobin electrophoresis in this patient is most likely to reveal which of the following predominant hemoglobin patterns?

Question

A 5-year-old boy is brought to the office by his parents to establish medical care.  The family recently immigrated to the United States from Nigeria.  Both parents have sickle cell trait, and the patient was diagnosed with homozygous sickle cell disease (HbSS) at the age of 6 months.  He has had several prior vasoocclusive crises and takes folic acid and hydroxyurea.  Physical examination shows no abnormalities.  Hemoglobin electrophoresis in this patient is most likely to reveal which of the following predominant hemoglobin patterns?

Quizplus · Accepted Answer

11ec160b_36ea_787a_9249_39fdf8263424_MD0001_00 In healthy children and adults, the predominant hemoglobin is hemoglobin A (HbA), which contains a pair of alpha and beta globulins. However, small quantities of other hemoglobin types are also present; these include hemoglobin A2 (HbA2), which contains a pair of alpha and delta globulins, and hemoglobin F (HbF), which contains a pair of alpha and gamma globulins. In homozygous sickle cell disease (sickle cell anemia), there are point mutations in both beta globulin genes that substitute valine for glutamate at position 6. This generates a new type of hemoglobin called hemoglobin S (HbS), which is composed of a pair of alpha and a pair of beta sickle globulins. HbS polymerizes when deoxygenated, reducing erythrocyte deformability and promoting painful vasoocclusion and chronic hemolysis. Because patients with sickle cell anemia have mutations in both beta globulin genes, they are unable to produce HbA (Choices B, C, and D). However, forms of normal hemoglobin that do not contain beta globulin (eg, HbF, HbA2) are present at normal or mildly increased levels. Raising the concentration of these normal hemoglobins is particularly helpful because it dilutes HbS, preventing it from polymerizing. Therefore, hydroxyurea, which increases HbF production, is often administered to limit symptoms and complications of the disease. (Choice E) Patients with hemoglobin SC disease have 1 beta globulin with the sickle mutation and 1 beta globulin with a mutation that substitutes lysine for glutamate at position 6. They produce two predominant hemoglobins: HbS and Hemoglobin C, the latter of which is not seen in sickle cell anemia as there is no hemoglobin C mutation. Educational objective: Homozygous sickle cell disease is marked by a point mutation in both beta globulin genes. This leads to the generation of a new predominant hemoglobin called hemoglobin S (HbS), which polymerizes when deoxygenated. Because hemoglobin F (HbF) prevents HbS polymerization, hydroxyurea is often administered to increase HbF levels and reduce complications of the disease.

A 5-Year-Old Boy Is Brought to the Office by His