Expanded Genome-Wide Association Study Meta-Analysis of Psoriasis Expands the Catalog of Common Psoriasis-Associated Variants.

Psoriasis is a complex immune-mediated disease of skin and joints with a prevalence of about 2%. Previous genetic association studies have identified more than 60 psoriasis susceptibility loci, 47 of which were identified in Caucasians. To further understand the genetic architecture of this disease, we conducted the largest meta-analysis of genome-wide association studies (GWAS) for psoriasis to date, including data from eight different Caucasian cohorts (seven GWAS and one Immunochip dataset), with a combined effective sample size of more than 39,000 individuals. Approximately half (n = 22) of the 47 European-origin loci were identified in cohorts containing a large proportion (≥50%) of samples genotyped using the Immunochip (Bowes et al., 2015; Stuart et al., 2015; Tsoi et al., 2012a, 2015), a platform that focuses on genetic variants from promising signals identified in previous association studies of autoimmune diseases (Stuart et al., 2015). However, restricting analysis to markers genotyped (∼110,000) (Tsoi et al., 2012b) or well-imputed (∼700,000) (Tsoi et al., 2015) on the Immunochip limits exploration of the full genome for susceptibility loci.