The occurrence of systemic lupus erythematosus in two kindreds in association with selective IGA deficiency.

The families of two patients with SLE and IgA deficiency were examined. A study of the first patient's family revealed that IgA deficiency was determined by an incompletely penetrant autosomal dominant gene not linked to the HLA locus. Antinuclear antibodies, found in consanguineous and nonconsanguineous relatives were not related to the presence of IgA deficiency or any HLA haplotype. The second patient and his father with antinuclear, anti RBC, and antithyroid auto-antibodies shared an HLA haplotype not present in other sibs. IgA deficiency was not inherited in this family but may have influenced the expression of disease in the propositus or could have resulted from the disease itself.