Adult-Onset Still Disease (AOSD).

Adult-onset Still disease (AOSD) is an uncommon clinical entity that predominantly affects young adults. One of the most common presentations of the disease is fever of unknown origin. Early diagnosis can be difficult because fever of unknown origin is more commonly seen with other conditions such as malignancy or infection. Ambiguity in presentation and lack of serologic markers make diagnosis difficult. We describe here an 18-year-old African-American man who presented with fever, sore throat, and arthritis at initial admission, with serology positive for both Mycoplasma pneumonia and Epstein-Barr infection. The patient was discharged without improvement. He was then readmitted with persistence of initial symptoms and, at that stage, he fulfilled the proposed diagnostic criteria of AOSD. The purpose of this case report is to describe the triggering infections that can initially mislead diagnosis and to review the literature about AOSD from a primary care perspective.