Follow-Up Study of the First Genome-Wide Association Scan in Alopecia Areata: IL13 and KIAA0350 as Susceptibility Loci Supported with Genome-Wide Significance

Recently, the first genome-wide association study (GWAS) of alopecia areata (AA) was conducted in a North-American sample, and this identified eight susceptibility loci surpassing genome-wide significance. The aim of the present follow-up association analysis was to confirm five of these eight loci (single-nucleotide polymorphisms (SNPs) from the CTLA4, IL-2RA, and HLA regions were not included due to previous own findings) and test 12 other loci from the GWAS, which did not surpass the threshold for genome-wide significance. Twenty-three SNPs from the 17 loci were investigated using a sample of 1,702 Central European AA patients and 1,723 controls. Of the five loci with previously reported genome-wide significance, association was confirmed for all of these: ULBP3/ULBP6, PRDX5, IL-2/IL-21, STX17, and IKZF4/ERBB3 (P-value <0.05). To detect robust evidence for association among the 12 other loci, a meta-analysis of the present association data and the data of the recent GWAS was performed. Genome-wide significant association was found for rs20541 (P-comb = 7.52 x 10(-10); odds ratio (OR) = 1.30 (1.23-1.38)) and rs998592 (P-comb = 1.11 x 10(-11); OR = 1.28 (1.21-1.36)), thus establishing IL-13 and KIAA0350/CLEC16A as susceptibility loci for AA. Interestingly, IL-13 and KIAA0350/CLEC16A are susceptibility loci for other autoimmune diseases, supporting the hypothesis of shared pathways of autoimmune susceptibility.