Acute appendicitis complicating infectious mononucleosis: case report and review.

Acute appendicitis is an uncommon complication of infectious mononucleosis (IM) and can readily be misdiagnosed because of the acute abdominal pain with which patients with IM occasionally present. A case report is presented of a patient with IM who developed acute appendicitis during the acute phase of the illness. The appendicitis progressed to the formation of an abscess, which was evacuated at surgery. Histologic examination of the appendix showed absence of lymphoid follicles in the mucosal layer and intense lymphoid infiltration of the mucosa and submucosa by a mixed diffuse proliferation of lymphoid cells with groups of immunoblasts scattered among them. The lymphoid infiltrate was mainly composed of T lymphocytes; the anticomplementary immunofluorescent staining of the appendix for EBNA (Epstein-Barr nuclear antigen) was negative. Three cases of appendicitis complicating IM published in the literature are reviewed. All had clinical and histopathologic features similar to those of our patient and were cured after surgery. Our case report together with the literature review confirms that appendicitis in the acute phase of IM has distinct clinical and histopathologic features and thus has to be considered a true complication of IM rather than merely a simultaneous disease.