Fever of unknown origin and pharyngitis as harbingers of natural killer/T-cell lymphoma: A case report highlighting diagnostic challenges.

Fever of unknown origin is one of the most challenging clinical symptoms, with complex etiologies including infections, malignancies, and rheumatic immune diseases. Lymphoma is a common malignant tumor associated with fever of unknown origin, and its early diagnosis is often difficult because routine laboratory tests and imaging manifestations may fail to provide a definitive diagnosis. Here, we report the case of a patient with natural killer/T-cell lymphoma who primarily presented with long-term fever and pharyngodynia. The patient sought medical care at several hospitals and underwent multiple laryngoscopies and a biopsy of the tongue base. After >3 months from the time of initial presentation, the diagnosis was ultimately confirmed through the second biopsy of the tongue base. The case highlights the diagnostic challenges of lymphoma with atypical symptoms in the context of fever of unknown origin and underscores the role of infectious disease physicians in diagnosing noninfectious diseases related to fever of unknown origin.