Transient erythroid hypoplasia in a patient on long-term co-trimoxazole therapy.

Introduction Although co-trimoxazole ('Septrin', 'Bactrim') is in common use, the incidence of associated erythropoietic disturbance is low. This is surprising, since the trimethoprim component has been shown to have some action on human dihydrofolate reductase (Hitchings, 1969) and the sulphamethoxazole might be expected to cause haematological complications as do other sulphonamides (Laurence, 1966). It therefore seemed of interest to report this case of red cell hypoplasia, probably attributable to an immunological reaction to the sulphamethoxazole.