A Case of Infectious Mononucleosis With Peritonsillar Abscess in a Middle-Aged Patient.

Infectious mononucleosis (IM) is common among young adults but often presents with nonspecific symptoms in middle-aged and older individuals. Cases of IM complicated by peritonsillar abscess (PTA) are uncommon. We report the case of a 41-year-old woman who presented to a local clinic with a sore throat and was initially diagnosed with acute tonsillitis. She was referred to our department after unsuccessful antibiotic and steroid therapy. Because of progressive difficulty with oral intake and laryngeal edema observed on flexible laryngoscopy, she was admitted for close monitoring and supportive care. Epstein-Barr virus (EBV) serology confirmed primary EBV-related IM. On the third hospital day, contrast-enhanced computed tomography (CT) was performed owing to a marked increase in C-reactive protein (CRP) levels, revealing a right-sided PTA. Aspiration drainage yielded oral commensal flora, and the patient responded favorably to antibiotic therapy. The patient improved clinically following drainage and antibiotic therapy and was discharged without recurrence. Even after a diagnosis of IM is established, secondary bacterial infection may occur, leading to PTA; therefore, vigilant clinical monitoring throughout the disease course is essential.