Autoimmune diseases and autoantibodies in the first degree relatives of patients with systemic sclerosis.

OBJECTIVE: To determine aggregation of autoimmune diseases in the first degree relatives (FDR) of patients with systemic sclerosis (SSc) and to investigate frequencies of antinuclear antibodies (ANA) and other autoantibodies in the FDRs and spouses of patients with SSc. METHODS: Information on FDRs including history of autoimmune disease was obtained from unrelated SSc probands in the Scleroderma Family Registry and DNA Repository. FDRs were contacted to verify any reported autoimmune diseases. The prevalence of autoimmune disease in probands' families was compared with the corresponding prevalence in controls' families as reported in the literature. Furthermore, sera from probands' FDRs and spouses in addition to unrelated controls were investigated for the presence of autoantibodies (ANA). RESULTS: We investigated 4612 FDRs of 1071 SSc probands. SSc probands with anti-centromere antibodies (ACA) and limited disease type were more likely to report familial autoimmunity (p=0.022 and p=0.041, respectively). The four most prevalent autoimmune diseases among SSc probands' FDRs were hypothyroidism (4%), Rheumatoid arthritis (1.5%), hyperthyroidism (1.3%) and systemic lupus erythematosus-SLE (0.4%). Compared to control families, SLE, hypothyroidism and hyperthyroidism were more common in SSc probands' families. The most striking increase for familial prevalence was observed in SLE (OR=16.98, 95% CI=1.02-227.82, p=0.004). ANA was present in 14.2% of probands' FDR's and 8.6% of spouses and did not differ from the prevalence of ANA among controls (p=0.124 and p=0.477, respectively). Only two FDRs of probands had ACA while none had anti-topoisomerase antibodies. CONCLUSION: Our study implies varying degrees of risk for familial autoimmunity among subtypes of SSc and provides further support for common genetic and potentially environmental factors leading to SSc and SLE.

Polymorphisms in TBX21 and STAT4 increase the risk of systemic sclerosis: evidence of possible gene-gene interaction and alterations in Th1/Th2 cytokines.

OBJECTIVE: Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. Dysregulation of the immune system, including the Th1/Th2 cytokine balance, is central to the pathogenesis of SSc. This study was undertaken to investigate the hypothesis that single-nucleotide polymorphisms (SNPs) in TBX21 and STAT4, both of which are critical transcription factors that regulate the Th1/Th2 balance, are associated with SSc susceptibility. METHODS: We tested SNPs in TBX21 and STAT4 for association with SSc in 2 independent cohorts, the SSc Registry cohort (880 SSc cases and 507 controls) and the University of Texas SSc cohort (522 cases and 531 controls). Additional white control genotypes were obtained from public repositories. We also investigated for gene-gene interactions. Plasma cytokines and whole blood gene expression profiles were examined to determine functional effects of these SNPs. RESULTS: Multiple SNPs in TBX21 and STAT4 were found to be associated with SSc. In a combined analysis of 902 SSc patients and 4,745 controls, TT genotyping of the TBX21 rs11650354 variant revealed a recessive pattern for disease susceptibility (Pcorr=1.4x10(-15), odds ratio 3.37, 95% confidence interval 2.4-4.6). In an analysis of 1,039 SSc patients and 3,322 controls, the A allele of the STAT4 variant rs11889341 was associated with increased SSc susceptibility in a dominant pattern (Pcorr=2.4x10(-5), odds ratio 1.29, 95% confidence interval 1.2-1.5). Furthermore, we identified gene-gene interaction among the TBX21 and STAT4 variants, such that the STAT4 genotype increased the risk of SSc only in the TBX21 CC genotype group. SSc patients carrying the TBX21 CC genotype had higher interleukin-6 (IL-6) and tumor necrosis factor alpha levels, and those with the TT genotype had elevated IL-2, IL-5, IL-4, and IL-13 (Th2) levels, compared with controls. Whole blood expression profiles revealed dysregulation of type I interferon pathways in the CC group and T cell pathways in the TT group of the TBX21 SNP. CONCLUSION: The present results, from studies of 2 independent cohorts, indicate that SNPs in TBX21 and STAT4 contribute uniquely and interactively to SSc susceptibility, leading to altered cytokine balance and immune dysregulation.