Azathioprine-associated pure red cell aplasia.

Azathioprine-associated pure red cell aplasia in patients with a renal allograft is a rare complication. Although immunological inhibition of erythroid progenitor cell has been suggested, the cause of this phenomenon remains unclear. The patient we describe showed a decrease in the number of erythroid progenitor cells and no evidence for the presence of a serum inhibitor of these precursor cells. Discontinuation of azathioprine was associated with a complete recovery from anaemia as well, with an increase in the number of erythroid progenitor cells.