A 30-year-old woman of African descent has chronic hemolytic anemia with splenomegaly. Her peripheral smear shows spherocytes and osmotic fragility is increased. Eosin-5-maleimide (EMA) binding test is markedly reduced. The most likely protein deficient is:

• A Band 3 (anion exchanger 1), leading to hereditary spherocytosis
• B Spectrin-ankyrin complex deficiency in hereditary spherocytosis ✓
• C Pyruvate kinase deficiency causing hemolysis
• D G6PD deficiency causing oxidant-induced hemolysis

Explanation

The EMA binding test measures binding to Band 3 and Rh-related proteins on red cell membranes; reduced EMA binding confirms hereditary spherocytosis (HS), with the most common underlying defects being spectrin (alpha or beta), ankyrin, or Band 3 mutations disrupting vertical protein-lipid bilayer interactions. While Band 3 loss also reduces EMA binding (option A), spectrin-ankyrin defects are the most common molecular basis worldwide. Pyruvate kinase and G6PD deficiencies cause hemolysis by different mechanisms and do not affect EMA binding.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.