Histoplasmosis in an off-trail Hiker receiving ustekinumab: Implications for Preventive and diagnostic strategies for patients receiving anti-IL-12/23 therapy.

Ustekinumab, an IL-12/23 inhibitor, is an important agent in treatment of inflammatory bowel disease and psoriasis. Clinical trials have not demonstrated significantly increased infection risk with ustekinumab. We report a case of disseminated histoplasmosis in the setting of ustekinumab and methotrexate following a hike in the Catskill Mountains, a region not commonly associated with Histoplasma encapsulatum. To our knowledge, this is the first reported case of newly acquired histoplasmosis complicating treatment with ustekinumab.