Azathioprine-induced pure red cell aplasia: case report and review.

The major adverse effect of azathioprine is its myelotoxicity, with leukocytes being affected more commonly than the other bone marrow elements. Although megaloblastic change is frequent, reportedly seen in 16% to 82% of bone marrow aspirates, long-term use of azathioprine rarely causes severe anemia. We report a case of refractory pure red cell aplasia resulting from long-term use of azathioprine in a renal transplant recipient and examine the possible underlying mechanisms. There was no response to dose reduction or to erythropoietin administration. However, there was immediate recovery after complete drug withdrawal. A review of the literature revealed that only ten cases of azathioprine-induced red cell aplasia have so far been described, all in transplant recipients.