Splenic, Nonhairy, B-Cell Lymphoma Presenting as Fever of Unknown Origin.

Fever of unknown origin (FUO) is a common diagnostic dilemma faced by internists on a fairly regular basis. A wide variety of infectious, autoimmune, and neoplastic conditions can present with FUO. Splenic B-cell lymphoma/leukemia with prominent nucleolus (SBLPN), formerly known as hairy cell leukemia-variant, is a hematologic malignancy that often presents with massive splenomegaly and pancytopenia. Initial presentation of SBLPN as FUO is exceedingly rare. Here, we present the case of an elderly gentleman in his 80s who presented with fever, night sweats, weight loss, and recurrent falls. He was subsequently diagnosed with SBLPN after 6 weeks of extensive diagnostic evaluation. The practicing internist needs to be aware of this initial presentation of SBLPN as FUO and have a low suspicion to proceed with a bone marrow aspiration and biopsy to clench the diagnosis in the right clinical context.