A syndrome marked by gross functional impairment of both humoral and cell-mediated immunity and by susceptibility to fungal, bacterial, and viral infections. Although the disorder may occur sporadically, most commonly it is inherited and transmitted as an X-linked or autosomal recessive trait. If untreated, infants rarely survive beyond 1 year. It is important that the disease be recognized early and that patients not be given live viral vaccines or blood transfusions. The immunologic defects may be repaired by stem cell transplantation. The optimal donor is an HLA-identical family member of the patient.