Macrocytosis and pure RBC anemia caused by azathioprine.

Red blood cell macrocytosis is a wellknown complication of azathioprine therapy. In a group of 91 patients receiving azathioprine immunosuppressive therapy for renal graft, the mean corpuscular volume determined by an electronic cell counter was substantially higher than in the normal population. Selective erythroid hypoplasia is another known but much less frequent complication of azathioprine use. The case of a child who had a selective erythroid hypoplasia while receiving azathioprine immunosuppressive therapy for renal graft is reported. The patient recovered as the drug therapy was discontinued. With progressive reintroduction of the drug, a second decrease in the hemoglobin was seen when a dose of 2 mg/kg was reached although with a smaller dose, no recurrence of anemia was observed.