A 28-year-old woman from West Africa presents with fatigue and jaundice. Her CBC reveals Hb 8.2 g/dL, MCV 75 fL, reticulocyte count 9%, and the peripheral smear shows target cells, sickle-shaped cells, and Howell-Jolly bodies. Hemoglobin electrophoresis shows HbS 92%, HbF 6%, HbA2 2%, HbA 0%. What is the mechanism of her anemia?

• A Hemolysis due to polymerization of deoxygenated HbS ✓
• B Impaired heme synthesis due to iron deficiency
• C Bone marrow failure from repeated vaso-occlusive infarcts
• D Autoimmune destruction of RBCs by warm IgG antibodies

Explanation

Sickle cell disease (HbSS) results from a point mutation (Glu→Val at position 6 of the beta-globin chain), causing deoxygenated HbS to polymerize into rigid tactoids that distort the red cell into the sickle shape. This leads to chronic hemolysis (elevated reticulocytes, jaundice) and vaso-occlusion. Howell-Jolly bodies indicate functional asplenia from repeated splenic infarcts. Iron deficiency causes microcytosis without hemolysis or sickle forms; bone marrow failure would suppress reticulocytes.

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

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Written and medically reviewed by the StethoPrep medical team.