Different familial association patterns of autoimmune diseases between juvenile-onset systemic lupus erythematosus and juvenile rheumatoid arthritis.

The aim of this study was to determine if the prevalence of autoimmune disorders in the relatives of patients with systemic lupus erythematosus (SLE) is greater than that of relatives of patients with juvenile rheumatoid arthritis (JRA). Interviews were used to obtain histories of the following autoimmune disorders among living or deceased first-, second-, and third-degree relatives of 91 SLE and 110 JRA families: ankylosing spondylitis, SLE, rheumatoid arthritis (RA), JRA, multiple sclerosis, juvenile dermatomyositis, Sjögren's syndrome, myasthenia gravis, psoriasis, and thyroid diseases. There were statistically significant differences between the SLE and JRA probands in mean age and gender ratio (19.1 +/- 4.8 vs 14.0 +/- 5.5 years; M (male)/F (female): 17/74 vs 62/48, p<0.005). The prevalence rate of autoimmune diseases in relatives of SLE families (20.9%) was greater than in JRA families (11.8%), but not statistically significantly so. The mean age (18.0 +/- 5.3 vs 14.0 +/- 4.3 years), mean age at diagnosis (13.4 +/- 4.3 vs 7.9 +/- 3.9 years) and gender ratio (F/M, 16/3 vs 5/8) of the patients with affected relatives between these 2 groups all had statistically significant differences. A higher prevalence of SLE in relatives was found in SLE families than in JRA cases. Furthermore, this study revealed a higher incidence of autoimmune disorders among second- and third-degree relatives of SLE or JRA probands versus first-degree ones, especially sisters (including 1 pair of twins) and the maternal aunt in SLE families. These data demonstrate that the prevalence of autoimmune disorders in the relatives of patients with SLE is greater than those of relatives of patients with JRA. This suggests that clinically different autoimmune phenotypes may share common susceptibility genes, which may act as risk factors for autoimmunity.