Persistent megaloblastic anemia: a diagnostic dilemma.

A patient with sickle cell trait and pernicious anemia in relapse may appear to have sickle thalassemia because HbA2 levels can be elevated and the peripheral blood smear may contain target cells, teardrop cells, and eliptocytes. A normal hemoglobin alpha:beta chain ratio, a megaloblastic bone marrow, and correction of the abnormal hematologic morphology after administration of vitamin B12 will establish the correct diagnosis.