Familial Burkitt's lymphoma. Association with altered lymphocyte subsets in family members.

Two sisters in a white American family died of Burkitt's lymphoma at ages 11 and 22 years, after dramatic but transient responses to chemotherapy. Studies of peripheral blood from two healthy brothers and the mother showed an increased percentage of polyclonal B cells (13 to 28 percent; normal, less than 10 percent), and a decreased helper:suppressor T cell ratio (1.0 to 1.5; normal, 1.5 to 2.5). The mother and one brother also had a low fraction of total circulating T cells (24 to 45 percent; normal, 60 to 75 percent). An inherited disturbance of the lymphocytes in family members may have predisposed the sisters to Burkitt's lymphoma; no environmental carcinogens were identified.