Reversible pure red cell aplasia associated with diphenylhydantoin therapy

Pure red cell aplasia (PRCA) is characterised by an anaemia with reticulocytopenia but with normal leukocyte and platelet counts, and a bone marrow with the selective absence of erythroid precursor cells. Drug-induced PRCA is a rare cause of secondary erythroid aplasia, but distinct from the primary and most secondary forms, it is usually acute and fully reversible upon withdrawal of the causative drug. We report a 36 year-old Chinese man who developed diphenylhydantoin associated PRCA two months after commencing the treatment. Reappearance of reticulocytes was observed six days following the cessation of diphenylhydantoin therapy and the haemoglobin level rose to normal one month later. The extreme rarity of this adverse reaction to a drug used so widely strongly suggests an individual predisposition.