An adult found to have mild anemia with MCV 64 fL undergoes hemoglobin analysis. Results show 8% HbH, normal amounts of HbA2, and no increase in HbF. Red cell inclusions are seen on supravital staining. This pattern results from:

• A Deletion of three of the four alpha globin genes ✓
• B Deletion of all four alpha globin genes
• C Deletion of both beta globin genes
• D Deletion of one of the four alpha globin genes

Explanation

Alpha thalassemia involves four gene loci. Deleting three leaves such severe alpha chain deficit that excess beta chains pair into tetramers forming HbH, which precipitates as inclusions and shortens red cell survival, producing hemolytic microcytic anemia. One gene deletion gives a silent carrier state, two give alpha thalassemia trait, and all four cause Hb Bart hydrops fetalis, lethal in utero. Beta gene deletions raise HbA2 and HbF, which are normal here.

Reference: Williams Hematology, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.