The HLA region is highly polymorphic and individual SNPs at the HLA region are commonly part of more than one HLA allele and haplotype. The GWAS analysis of the associating locus (6p21.32) at the HLA region showed multiple SNPs associating with ASPD and the LD was carried over from BTNL2 gene to as far as the HLA-DQB1 gene region (Figure 3b). We observed that there were no directly genotyped SNPs at the HLA-DRB1 locus that would conceivably have depicted whether the highest association was indeed over HLA-DRA or perhaps over the HLA-DRB1 locus. It was also possible that some of the associating SNPs tagged an independent HLA allele, or that specific HLA alleles or their coding polymorphisms, rather than single SNPs, would drive the association with ASPD. The HLA region is also known to be difficult for probe designing or to impute with SNPs, therefore, we imputed the GWAS genotype data with the classical HLA alleles (Supplementary Information), and studied whether specific HLA alleles would associate with ASPD. We detected four HLA alleles at HLA-DRB1 and HLA-DQA1 genes with similar
