Fever of Unknown Origin in a 17-Year-Old Girl.

Fever of unknown origin (FUO) is defined as fever (>101°F) that lasts more than three weeks and for which a cause is not found within seven days of hospital evaluation. FUO has a broad list of differentials - infection, inflammatory diseases, and malignancy. A detailed history and meticulous clinical examination with thorough and stepwise investigations lead to a diagnosis in only two-thirds of cases. In this article, we present a 17-year-old adolescent girl, with no significant past medical history, who presented with FUO during the COVID pandemic. A high index of suspicion and extensive investigations revealed the final diagnosis.