Fever of unknown origin: a challenging case.

We report a case of Cogan's syndrome presenting as fever of unknown origin in a 31-year-old woman who was admitted to the hospital with a 7-week history of fever, night sweats and other constitutional symptoms. The diagnosis remained elusive despite numerous investigations, and the patient subsequently developed rash, episcleritis, dizziness and sensorineural hearing loss. While initially thought to be a postinflammatory response to a previous infection, confirmation of the rash as a vasculitis together with the audiovestibular and ocular involvement led to a clinical diagnosis of Cogan's syndrome. This was further corroborated by resolution of her symptoms once immunosuppressive therapy was instituted. Early recognition of Cogan's syndrome is crucial to reducing the risk of serious complications through the timely initiation of treatment.