PERIPHERAL-BLOOD LYMPHOCYTE APOPTOSIS - A CLUE TO THE DIAGNOSIS OF ACUTE INFECTIOUS-MONONUCLEOSIS

Objective.-To describe the morphology and significance of apoptotic ly mphocytes in peripheral blood smears of patients with acute infectious mononucleosis. To our knowledge this has not been previously reported . Design.-Peripheral blood smears from 27 patients with a positive het erophile antibody test were collected and reviewed for the presence of apoptotic lymphocytes. Flow cytometry was performed on three cases to document the previously described low expression of bcl-2 in lymphocy tes in infectious mononucleosis. Four control patient populations comp rising 80 cases were similarly screened for the presence of apoptotic lymphocytes. Setting.-The specimens were collected over a 3-month peri od in two laboratories at our tertiary care hospital; all specimens we re processed according to a standard protocol. Patients.-Young adult m ilitary recruits and their spouses, military dependent adolescents, an d retired military personnel. Results.-Twenty-four (88.9%) of 27 perip heral blood smears of patients with acute infectious mononucleosis con tained readily identifiable apoptotic lymphocytes. Three (3.75%) of 80 control peripheral blood smears were identified with rare apoptotic l ymphocytes, all occurring in patients with viral upper respiratory inf ections. Conclusions.-The finding of apoptotic lymphocytes in a periph eral blood smear is useful in the differential diagnosis of infectious mononucleosis and neoplastic hematolymphoid processes.