Background Genome-wide association studies (GWASs) have revealed a large number of genetic risk loci for many autoimmune diseases. One clear finding emerging from the published genetic studies of autoimmunity is that different autoimmune diseases, such as psoriasis and systemic lupus erythematosus (SLE), share susceptibility loci. Our study explores additional susceptibility loci shared by psoriasis and SLE in the Chinese Han population.

Methods In total, 20 single nucleotide polymorphisms (SNPs) in 17 previously reported psoriasis susceptibility loci and 34 SNPs from 24 previously reported SLE susceptibility loci were investigated in our initial psoriasis and SLE GWAS dataset. Among these SNPs, we selected two SNPs (rs8016947 and rs4649203) with association values of p<5×10⁻² for both diseases in the GWAS data for further investigation in psoriasis (7260 cases and 9842 controls) and SLE (2207 cases and 9842 controls) using a Sequenom MassARRAY system.

Results We found that these two SNPs (rs8016947 and rs4649203) in two loci (NFKBIA and IL28RA) were associated with psoriasis and SLE with genome-wide significance (P_combined<5×10⁻⁸ in psoriasis and P_combined<5×10⁻⁸ in SLE): rs8016947 at NFKBIA (P_combined-psoriasis=3.90×10⁻¹⁰, P_combined-SLE=1.08×10⁻¹³) and rs4649203 at IL28RA (P_combined-psoriasis=3.91×10⁻¹², P_combined-SLE=9.90×10⁻⁹).

Conclusions These results showed that two common susceptibility loci (NFKBIA and IL28RA) are shared by psoriasis and SLE in the Chinese Han population.