Acquired hypogammaglobulinemia following infectious mononucleosis.

The case of a 17-year-old male who developed hypogammaglobulinemia following infectious mononucleosis is presented. The family history revealed that a male sibling had died some years earlier with encephalitis also following infectious mononucleosis. Laboratory investigations revealed adequate numbers of T and B cells and normal proportions of helper and suppressor T lymphocytes but poor in vitro responses to mitogens and an absence of hypersensitivity to skin test antigens. Serial serological examinations for Epstein-Barr virus antibodies indicated a primary immune response to this virus in a hypogammaglobulinemic individual. The patient probably represents a case of the X-linked lymphoproliferative syndrome. The unique feature of the present case is the demonstration of Epstein-Barr virus-specific T-cell memory. The significance of this finding and the variable expression of this syndrome in two members of the same family are discussed.