A familial syndrome of susceptibility to chronic active Epstein-Barr virus infection.

In two members of a family (daughter and father) active Epstein-Barr virus (EBV) infections persisted over periods of 4 and 3 years respectively (possibly 10 years in the father). Both had persistent splenomegaly and occasional bouts of unexplained fever but lived otherwise normal lives. The other members of the family (mother and son) were healthy. The titres of antibody to the EBV viral capsid antigen (VCA) and early antigen (EA) were extremely high in the daughter's blood, whereas the titres of antibody to the Epstein-Barr nuclear antigen were low in the daughter's blood and undetectable in the father's. Target cells of the EBV infection that were obtained from the daughter's blood were established in culture with great difficulty and showed increased expression of VCA and EA. Other immunologic investigations in the two patients revealed that the ratio of helper to suppressor T lymphocytes was inverted, natural killer-cell activity was abnormally low, lymphocyte responses to certain mitogens were depressed and there was a serum factor blocking mitogen-induced transformation. The possibility that the patients' unusual susceptibility to EBV infection represented an inherited syndrome (perhaps X-linked) is discussed.