100% N4-acetyl-sulfamethoxazole stone induced by Trimethoprim-Sulfamethoxazole in an HIV patient being treated for toxoplasmosis.

Trimethoprim-Sulfamethoxazole is a common antibiotic used to treat urinary tract infections, as well as a prophylactic agent in HIV patients with low CD4 counts. Exceedingly rare are stones consisting purely of its metabolite, N4-acetyl-sulfamethoxazole, and management strategies are not well documented in the literature. We present a case of a patient with HIV who was found to have obstructing ureteral calculi composed of 100% N4-acetyl-sulfamethoxazole. Our report contributes a unique case of a Bactrim-induced stone in an immunocompromised patient. Similar patients can be prophylactically treated with diuresis and urinary alkalinization, as well as consideration for alternative medication use.