Genome-wide association study of psoriasis in an Egyptian population

Psoriasis is a chronic inflammatory disorder of the skin, with genetic factors reportedly involved in the disease pathogenesis. Numerous studies reported psoriasis candidate genes. However, these tend to involve mostly in the European and Asian populations. Here, we report the first genome-wide association study (GWAS) in an Egyptian population, identifying susceptibility variants for psoriasis using a two-stage case-control design. In the first discovery stage, we carried out a genome-wide association analysis using the Infinium^® Global Screening Array-24 v1.0, on 253 cases and 449 control samples of Egyptian descent. In the second replication stage, 26 single-nucleotide polymorphisms (SNPs) were selected for replication in additional 321 cases and 253 controls. In concordance with the findings from previous studies on other populations, we found a genome-wide significant association between the MHC locus and the disease at rs12199223 (P_comb  = 6.57 × 10^-18 ) and rs1265181 (P_comb  = 1.03 × 10^-10 ). Additionally, we identified a novel significant association with the disease at locus, 4q32.1 (rs12650590, P_comb  = 4.49 × 10^-08 ) in the vicinity of gene GUCY1A3, and multiple suggestive associations, for example rs10832027 (P_comb  = 7.28 × 10^-06 ) and rs3770019 (P_comb  = 1.02 × 10^-05 ). This proposes the existence of important interethnic genetic differences in psoriasis susceptibility. Further studies are necessary to elucidate the downstream pathways of the new candidate loci.