Pseudoappendicitis preceding infectious mononucleosis.

In patients with infectious mononucleosis, abdominal pain is usually attributed to visceral enlargement. A teenage girl with symptoms of appendicitis was found at laparotomy to have mesenteric adenitis. Postoperatively, she developed classic features of Epstein-Barr virus (EBV)-induced mononucleosis. The lymphoproliferation characteristic of EBV infection can cause severe localized abdominal pain that predates the onset of mononucleosis.