RESUMO
Infectious mononucleosis (IM) is a viral illness caused by the Epstein-Barr virus that typically manifests with pharyngitis, lymphadenopathy, and fatigue. In rare cases, IM can cause acute appendicitis. We present the case of an 18-year-old female who arrived at the emergency department with worsening abdominal pain and an ongoing cough. Initial imaging showed a questionably dilated appendix, and a follow-up examination revealed cervical lymphadenopathy. She later returned to the ED with severe abdominal pain, clinical signs of acute appendicitis, and a positive monospot test, which led to an appendectomy. This case illustrates the need for complete history taking and thorough physical examination in patients with acute appendicitis, as their condition may be due to an atypical underlying cause.