Fine Mapping of Eight Psoriasis Susceptibility Loci

Psoriasis is a common immune-mediate disease identified through scaly patches of the skin. In this study we collected genotype information on 5,067 samples of European ancestry as a follow-up study of our initial GWAS (Nair et al. 2009). We designed an Illumina iSelect custom genotyping array with 2,269 tagging SNPs in the eight known psoriasis susceptibility regions (MHC, IL12B, IL23R, IL23A, TNFAIP3, IL13, RNF114, and TNIP1). The custom array also included 5,463 SNPs outside the eight known susceptibility regions, which were selected based on their association p-values in a meta-analysis of HapMap-imputed genotypes of two published GWAS-CASP (Nair et al. 2009) and (Ellinghaus et al. 2010). After quality control we analyzed 4,806 samples (2,699 cases and 2,107 controls). Please note: The accession number for this dbGaP study was incorrectly listed in the relevant publication (Das et al., 2015, Eur. J. Hum. Genet 23:844-853) as phs000019.v1.p1.]]> We applied usual quality controls measures for inclusion/exclusion criterion for our cases/controls. We removed samples with less than 95% genotyping rate or with extreme heterozygosity. We also removed samples that were duplicates or close relatives of other samples in the study (identified using the program relativeFinder) or with evidence of non-European ancestry (identified using principal component analysis).]]>