Mononucleosis-associated subacute sclerosing panencephalitis.

Three cases of coincidental infectious mononucleosis (I.M.) and subacute sclerosing panencephalitis (S.S.P.E.) in children are reported. In two of the cases, I.M. preceded the appearance of S.S.P.E. symptoms. The other case of S.S.P.E. was associated with apparent mononucleosis encephalitis. All three patients died within 3 months of S.S.P.E. being diagnosed and had pathological changes characteristic of that disease and raised levels of measles antibody. Two of the patients had apparent T-cell-associated abnormalities which suggested a degree of I.M.-associated immunosuppression. The relation between the two conditions remains obscure.