Occurrence of autoimmune diseases and autoantibodies in multicase rheumatoid arthritis families.

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Abstract
The presence of autoimmune diseases and autoantibodies has been studied in 237 individuals from 17 families with two or more members affected by rheumatoid arthritis (RA). Hyperthyroidism occurred significantly more frequently than in a local control population (p less than 0.05), but if the RA cases were excluded this significance was lost. Thyroid cytoplasmic and microsomal antibodies were significantly more common (p less than 0.001), and this remained true if RA sufferers were excluded (p less than 0.01). The prevalence of both clinical thyroid disease and circulating thyroid autoantibodies was similar in the families where RA was associated with HLA-DR4 and in those where no DR4 association was observed. RA and immune thyroid disease may, therefore, share a common inherited factor, but this is unlikely to be at the HLA-DR locus. Antinuclear factor (ANF) was found in association with RA and with HLA-DR3 within the RA group (p less than 0.02). Relatives of RA sufferers did not show any excess of ANF positivity. The prevalence of pernicious anaemia (PA) and gastric parietal cell antibody did not differ from the expected.