A 25-year-old male of African descent presents with chronic hemolytic anemia, spherocytes on peripheral smear, and negative Coombs test. His father has the same condition. Red cell osmotic fragility is increased. Eosin-5-maleimide (EMA) binding test shows reduced fluorescence. The most likely deficient protein is:

• A Spectrin (alpha or beta)
• B Glycophorin C
• C Protein 4.2
• D Band 3 (anion exchanger 1) ✓

Explanation

The EMA (eosin-5-maleimide) binding test primarily measures Band 3 protein expression on the red cell surface; reduced fluorescence indicates Band 3 deficiency. Band 3 mutations causing hereditary spherocytosis (HS) are the most common cause of HS in Southeast Asia and sub-Saharan Africa, in contrast to spectrin/ankyrin defects that predominate in northern Europeans. Band 3 (SLC4A1 gene) anchors the lipid bilayer to the cytoskeleton through ankyrin and protein 4.2; its deficiency leads to membrane vesiculation, spherocyte formation, and splenic trapping.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.