Hyperkalemic renal tubular acidosis induced by trimethoprim/sulfamethoxazole in an AIDS patient

A patient with the acquired immunodeficiency syndrome (AIDS) and sickle cell anemia presented to the University of Wisconsin Hospital on two separate occasions with pneumocystis carinii pneumonia (PCP). On both occasions he was treated with high-dose intravenous trimethoprim/sulfamethoxazole (TMP/SMX). Several days into each treatment course he developed hyper kalemia and systemic acidosis consistent with hyperkalemic renal tubular acidosis (RTA). The abnormalities resolved in the first instance with the addition of amphotericin B while continuing TMP/SMX, and in the second upon discontinuation of the TMP/SMX. While an increasing number of cases with TMP/SMX-induced hyperkalemia have been reported, hyperkalemic RTA is an uncommon complication of TMP/SMX therapy, occurring in patients with predisposing factors or acidosis such as aldosterone defects, medullary dysfunction and renal insufficiency.