An investigation of rheumatoid arthritis loci in patients with early-onset psoriasis validates association of the REL gene

Background Phenotypically diverse autoimmune conditions share common genetic susceptibility loci and underlying molecular pathways. Objectives By systematically searching for single nucleotide polymorphisms (SNPs) associated with another autoimmune disease, rheumatoid arthritis (RA), we aimed to elucidate novel genetic markers of psoriasis. Methods We investigated 18 SNPs, previously confirmed as being associated with RA, in a U. K. cohort of 623 patients with early-onset psoriasis (presenting before age 40 years), comparing them with 2662 control subjects. Results Our findings confirm the association of early-onset psoriasis with REL (rs13031237, P = 0.0027). The minor allele of REL had opposing effects upon susceptibility to disease in patients with psoriasis and RA. Conclusion Similar exploration of additional autoimmune loci and fine mapping of such regions may provide further insight into the genetics and molecular pathophysiology of psoriasis.