Malakoplakia: evidence for an acquired disease secondary to immunosuppression.

A 44-year-old man was maintained on prednisone and azathioprine after renal transplantation. One and a half years after transplantation, he developed multiple perianal Escherichia coli abscesses. These became chronic and resisted antibiotic therapy. Histologically, the lesions were typical of malakoplakia. Peripheral blood neutrophils and monocytes had impaired killing of Staphylococcus aureus and E. coli in vitro. No abnormality of hexose monophosphate pathway activity, tetrazolium dye reduction, lysosomal degranulation, or cyclic nucleotides could be demonstrated in either neutrophils or monocytes. Cholinergic agonists in vitro and in vivo did not improve bacterial killing by these cells. The infection resolved rapidly and bacterial killing returned to normal when the dose of azathioprine was reduced. Our findings, when considered with previous reports, suggest that there are different causes of malakoplakia and malakoplakia may be more common than previously thought. The etiology of malakoplakia should be identified for each patient if appropriate treatment is to be given.