Chronic infectious mononucleosis syndrome, pancytopenia, and polyclonal B-lymphoproliferation terminating in acute lymphoblastic leukemia.

A 17-year-old previously healthy girl is reported who developed acute infectious mononucleosis followed by progressive ill health over 20 months, associated with pancytopenia and a polyclonal B-lymphoproliferation, terminating in acute lymphoblastic leukemia (ALL). Epstein-Barr virus (EBV) was recovered from the patient's nasopharyngeal secretions; serologic titers of antibodies to EBV-associated antigens were compatible with a chronic persistent EBV infection. Plasma interferon levels were markedly elevated. EBV-specific cell-mediated immunity, as well as Natural killer (NK) cell activity were markedly deficient. Other studies of cell-mediated immunity revealed notable abnormalities, including abnormalities in T-cell subset ratios, and a serum blocker of autologous mitogen-induced lymphoproliferation. Humoral (plasma)-mediated, but not cell-mediated, suppression of hemopoiesis was demonstrated using in vitro erythroid and myeloid colony culture techniques. Immunophenotyping of the patient's bone marrow cells preterminally was consistent with ALL. Autopsy revealed pathologic changes of ALL in marrow and multiple organs. We conclude that our patient developed an EBV-driven lymphoproliferative disorder, with associated defective cell-mediated immunity and hemopoiesis. Ultimately, the patient's documented polyclonal lymphoproliferative state was superimposed by acute lymphoblastic leukemia.