Beta-Thalassemia Minor: The Daily PANCE Blueprint

The answer is C. Beta-thalassemia minor

A profoundly microcytic anemia that is far milder than the MCV suggests, with a high red cell count, normal iron studies, and an elevated hemoglobin A2, is beta-thalassemia minor — thalassemia trait. The defect is reduced synthesis of beta-globin chains; alpha chains are produced normally and accumulate in relative excess, so red cells are small and pale but are made in large numbers. That last point generates the most useful clue on the panel. In iron deficiency the marrow cannot build red cells, so both the MCV and the red cell count fall together. In thalassemia trait the marrow builds plenty of cells that are simply small, so the MCV is very low while the RBC count is normal or high. Formalize it as the Mentzer index — MCV divided by RBC count — where a value under 13 favors thalassemia and over 13 favors iron deficiency. Here 65 divided by 6.1 is about 10.7. Two more discriminators are doing work in this stem. The RDW is normal, because in thalassemia every cell is uniformly small, whereas iron deficiency produces a mixed population and a high RDW. And the iron studies are normal, which by itself excludes iron deficiency and makes the failed iron trial expected rather than puzzling. That failed trial matters clinically: these patients are frequently misdiagnosed and given iron for years, and unnecessary iron supplementation risks iron overload. Confirm with hemoglobin electrophoresis, where an elevated hemoglobin A2 above roughly 3.5% is diagnostic of beta-thalassemia trait. Note the contrast with alpha-thalassemia trait, in which electrophoresis is typically normal in adults and the diagnosis is one of exclusion confirmed by genetic testing. Management of beta-thalassemia minor is largely reassurance: no transfusions, no chelation, and no iron unless deficiency is separately proven. The essential intervention is genetic counseling, because two carriers can produce a child with beta-thalassemia major (Cooley anemia) — a transfusion-dependent disease presenting after six months of age as fetal hemoglobin declines, with growth failure, hepatosplenomegaly, extramedullary hematopoiesis producing frontal bossing and a “crew-cut” skull film, and death from iron-overload cardiomyopathy without chelation. Sorting the distractors: iron deficiency anemia is the main mimic but shows a low ferritin, low serum iron, high TIBC, high RDW, a low-to-normal RBC count, and it responds to iron; anemia of chronic disease is usually normocytic and only mildly microcytic, with a low serum iron but high or normal ferritin and a low TIBC in a patient with inflammatory illness; sideroblastic anemia shows ringed sideroblasts on iron-stained marrow with a high ferritin and high transferrin saturation, and is associated with alcohol, isoniazid, and copper deficiency; and lead poisoning produces basophilic stippling with abdominal pain, neuropathy, and an elevated blood lead level, none of which is present here.