Disseminated Histoplasmosis After Ustekinumab Treatment: Safe, But Is It the Safest?

ABSTRACT Ustekinumab (UST), an interleukin-12/23 inhibitor, is used in moderate-to-severe Crohn's disease. It is generally considered safer than tumour necrosis factor-α inhibitors. We report a case of a 62 year-old male patient with Crohn's disease who developed disseminated histoplasmosis after UST treatment, presenting with cholestatic jaundice, lymphadenopathy, and hepatomegaly. Endoscopic ultrasound guided biopsy revealed granulomatous hepatitis and lymphadenitis. Colonoscopy showed ileocolonic ulcerations with histopathology confirming noncaseating granuloma, Grocott-Gomori methenamine silver revealed yeast forms of histoplasmosis. This case highlights the need for high clinical suspicion of opportunistic even with UST, especially in tuberculosis endemic regions like India, where histoplasmosis may be under-recognized.