HLA-C and psoriasis: One example is the KIR, polymorphisms of which were found to be associated with PsA in case-control studies [43] but not identified as a genetic risk region in large-scale GWAS [13,14] although a functional consequence is likely since class I MHC molecules (including HLA-C*06:02 and -B*27) are ligands for these receptors [39–42] but not demonstrated in PsA or psoriasis to date.