['Phenotypically diverse autoimmune conditions share common genetic susceptibility loci and underlying molecular pathways.', '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.', '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.', '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.'] Does an investigation of rheumatoid arthritis loci in patients with early-onset psoriasis validate association of the REL gene?