A 28-year-old woman with sickle cell disease is found to have a concurrent alpha thalassemia trait (two alpha gene deletions). Which clinical outcome would you expect compared to a patient with sickle cell disease alone?

• A Milder disease with fewer vaso-occlusive episodes due to lower MCHC and HbS concentration ✓
• B More severe vaso-occlusive crises due to higher hemoglobin S polymerization
• C Development of hemoglobin H disease in addition to sickling
• D Increased risk of splenic sequestration due to reduced red cell deformability

Explanation

Co-inheritance of alpha thalassemia trait (2-gene deletion) with sickle cell disease reduces the mean corpuscular hemoglobin concentration (MCHC) and intracellular HbS concentration, which reduces the tendency for HbS polymerization. This results in fewer vaso-occlusive crises and a milder clinical course, though it does not prevent all complications. Alpha thalassemia trait does not produce HbH disease in combination with SCD, as only 2 (not 3) alpha genes are deleted.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.