A 22-year-old man with beta-thalassemia intermedia has splenomegaly and gallstones. Splenectomy specimen shows RBC precursors filled with precipitated globin inclusions. Electrophoresis of his hemoglobin reveals a fast-moving fraction accounting for about 5 percent of total hemoglobin. This fraction is composed of:

• A Gamma chain tetramers
• B Beta2 gamma2 tetramers
• C Alpha2 delta2 tetramers
• D Beta chain tetramers ✓

Explanation

Excess unmatched beta chains in beta-thalassemia self-associate into beta4 tetramers called hemoglobin H, which migrates rapidly on electrophoresis and forms inclusion bodies damaging erythrocyte membranes. Gamma4 is hemoglobin Bart's, seen in alpha-thalassemia and hydrops fetalis. Alpha2delta2 is hemoglobin A2, a normal minor component. No physiological beta2gamma2 hybrid exists since alpha-like and beta-like chains pair one of each, never two beta-like chains together.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.