Fever of unknown origin (FUO) caused by Kikuchi's disease mimicking lymphoma.

Fever of unknown origin (FUO) refers to infectious, neoplastic, or rheumatic/inflammatory disorders that present with fevers of 101 degrees F or greater for 3 weeks and that remain undiagnosed after an intensive in-hospital or outpatient workup. The noninfectious causes of FUO in adults are most often lymphomas or rheumatic/inflammatory disorders. Among the rare causes of rheumatic/inflammatory FUOs is Kikuchi's disease. Kikuchi's disease (Kikuchi-Fujimoto disease) is also known as histiocytic necrotizing lymphadenitis, a benign, self-limited disorder usually in middle-aged women of Asian descent. Cervical adenopathy is typical and often accompanied by leukopenia. In middle-aged adults patients presenting with an FUO, the presence of otherwise unexplained cervical adenopathy should suggest the possibility of lymphoma or, rarely, Kikuchi's disease.