In sickle cell disease, hydroxyurea is used to reduce the frequency of which complication?

• A. Hemophilia
• B. Lymphoma
• C. Leukemia
• D. Vaso-occlusive crises

Answer: (D)

The key idea is that hydroxyurea helps prevent painful complications in sickle cell disease by increasing fetal hemoglobin (HbF) production. HbF does not participate in the abnormal polymerization of HbS, so with more HbF the red cells are less likely to polymerize and sickle under low oxygen. This makes the red blood cells more flexible and reduces themselves from sticking in small vessels, leading to fewer vaso-occlusive events. The other conditions listed are not the targeted complication addressed by hydroxyurea in this disease context, and thus the reduction in vaso-occlusive crises is the most direct and meaningful clinical benefit. In practice, hydroxyurea therapy requires monitoring for cytopenias and other potential effects, but its main impact here is lowering the frequency of vaso-occlusive crises.