Fever of unknown origin: Chronic lymphatic leukemia versus lymphoma (Richter’s transformation)

Currently, malignancies are more common than infections as a cause of fever of unknown origin (FUO) in adults. Many malignant disorders are associated with fever, which may either be of the hectic–septic variety resembling an infectious disease or prolonged and low-grade. Neoplasms with either kind of fever may present as an FUO. The malignancies usually associated with fever are lymphoreticular malignancies involving the blood, liver, spleen, or bone marrow. Most malignancies do not have fever, e.g., chronic lymphatic leukemia (CLL), as part of their clinical presentation. We present a case of long-standing CLL in an elderly woman who presented with an FUO. Initially, it was thought that her FUO was caused by CLL or a CLL-related opportunistic infection. The naprosyn test was used in this patient with CLL and FUO to differentiate a malignant from an infectious etiology. Her response to naprosyn indicated that the etiology of her FUO was neoplastic rather than infectious. The absence of tonsillar enlargement and peripheral adenopathy, as well as the presence of fever, argued against CLL as the cause of her fever. Computed axial tomography scans showed central adenopathy in addition to splenomegaly. The presence of fever, splenomegaly, and central adenopathy indicated that the cause of her FUO was a lymphoma (Richter’s transformation) and not CLL.