Primary Infectious Mononucleosis Masquerading as Post-operative Fever in a Young Patient with Cemento-ossifying Fibroma of the Skull Base.

The typical presentation of infectious mononucleosis (IM) is characterized by a triad of fever, pharyngitis, and lymphadenopathy. Epstein-Barr virus (EBV) is the most common etiologic agent for IM. Humans are the reservoir for EBV, and it is transmitted via intimate contact between individuals. This case presents a 19-year-old male with recurrent cemento-ossifying fibroma of the skull base with a complicated post-operative course including bacterial meningitis, cerebrospinal fluid (CSF) leak, and intermittent fevers despite treatment with intravenous cefepime. Head computed tomography (CT) revealed a nonspecific subdural collection that could represent an empyema. However, exploratory craniotomy revealed no empyema. CT chest demonstrated bilateral hilar mediastinal lymphadenopathy and splenomegaly. Blood work for fever of unknown origin was positive for EBV immunoglobulin M, and EBV deoxyribonucleic acid 180,565 IU/mL. The diagnosis of EBV IM in this case was elusive because it presented post-operatively, symptoms aligned with the patient's CSF leak, and he reported no sexual or sick contacts. For post-operative young patients with recurrent fevers of unknown origin, it is important to consider EBV IM in the differential. Earlier diagnosis could have saved the patient unneeded tests, prevented surgical re-exploration, and resulted in a shorter hospital stay.