Family studies in common variable immunodeficiency.

The occurrence of cancer, immunodeficiency, and diseases with possible autoimmune aetiology were studied in 355 blood relatives of 12 patients with common variable immunodeficiency (CVID). The family members were identified through the patients and interviewed after completing a questionnaire, their diseases were medically confirmed by local general practitioners. In two families consanguineous marriages were identified with the coefficients of inbreeding of 0.03125 and 0.01563, respectively: one patient, a dizygotic twin of an unaffected sister, was a granddaughter of first cousins, the second patient was the third daughter of second cousins. These cases of CVID strongly support the autosomal recessivity of the underlying genes. One male patient with CVID was shown to be related to a patient with X-linked hypogammaglobulinaemia, both sharing a common carrier. The different clinical courses of their diseases suggest two genetically determined immunodeficiencies and genetic heterogeneity. No family had an unusual clustering of cancer. The occurrence of tumours in the blood relatives of CVID patients was not significantly higher than in the relatives of spouse controls. Immunological examination of 30 first degree relatives of the CVID patients revealed three children (2 males and 1 female) with selective IgA deficiency, in one boy combined with elevated serum IgE level. Four relatives with rheumatoid heart disease, 12 cases of gastric or duodenal ulcer, and 14 relatives with thyroid disease represented the most often encountered diagnoses with a possible autoimmune component in their aetiology.