[Pure red cell aplasia induced by erythromycin and furosemide effects on in vitro erythroid colony forming unit (CFU-E)].

A 84-year-old man was treated with antibiotics including erythromycin and a diuretic (furosemide) because of acute heart failure and pneumonia. During the treatment, he developed moderate anemia (Hb 8.7g/dl). His anemia improved after the treatment. He again developed marked anemia (Hb 6.3g/dl) during the second treatment with erythromycin and furosemide and received blood transfusions. Bone marrow aspiration study revealed severe erythroid hypoplasia (0.2%). He was referred to our hospital, but he was not treated because his hemoglobin levels and reticulocyte count increased (80%) and his bone marrow showed increased erythroblasts (41.5%). His anemia gradually improved without any treatment. We diagnosed the case as drug-induced pure red cell aplasia (PRCA). We cultured bone marrow cells obtained from the present case and four normal healthy volunteers by a plasma clot method to determine the effects of two drugs on the number of erythroid colony forming unit (CFU-E). Furosemide strongly inhibited the CFU-E colony formation in the patient, but the inhibition effect of erythromycin was moderate. Furthermore, CFU-E was markedly suppressed by a combination of erythromycin and furosemide in both patient and control materials. These results indicate that both furosemide and erythromycin were related to the occurrence of PRCA in this patient.