Chronic active mononucleosis.

A 16-year-old girl with 3 clinical episodes of mononucleosis during a period of more than 2 year is presented. The patient had persistently elevated VCA-IgM antibodies during follow-up for 15 months until she became EBNA-positive. This is a case of prolonged primary EBV infection and late seroconversion as clinical restitution and development of EBNA antibodies occurred 2 year after the onset of clinical illness.