Cumulative association of eight susceptibility genes with systemic lupus erythematosus in a Japanese female population.

Although large-scale studies established many susceptibility genes to systemic lupus erythematosus (SLE), effect of each gene is not sufficiently large to be used alone to identify individuals with strong genetic predisposition. In this study, we analyzed the cumulative number of risk alleles at eight established susceptibility loci, HLA-DRB1, IRF5, STAT4, BLK, TNFAIP3, TNIP1, FCGR2B and TNFSF13, in 282 Japanese female SLE and 222 healthy female controls. The average number of risk alleles was significantly increased in SLE (8.07±1.60) than healthy controls (7.02±1.64) (P=1.63 × 10(-12)). Significant gene-gene interaction was not detected. When the subjects carrying seven risk alleles were used as a reference, the odds ratio (OR) for individuals carrying 10 and 11-13 risk alleles were 4.17 (95% confidence interval (CI) 1.89-9.19, P=0.0002) and 8.77 (95% CI 1.92-40.0, P=0.0016), respectively. In contrast, subjects with ≤4 risk alleles were significantly decreased in SLE (OR 0.15, CI 0.03-0.67, P=0.007). The proportion of the patients with neurologic disorder was significantly increased in those carrying ≥10 risk alleles than those with <10 (OR 2.30, CI 1.09-4.83, P=0.025). This study suggested that the cumulative number of risk alleles may efficiently distinguish groups with high and low genetic predisposition to SLE and its severe manifestation.