The association with HLA-C*06:02 in psoriasis is particularly intriguing because only 3 of more than 12,000 different HLA-class I alleles show a strong disease linkage: HLA-B*27 with ankylosing spondylitis, HLA-B*51 with Behçet’s disease, and HLA-C*06:02 with psoriasis. This evidence concerns the gene HLA-B and ankylosing spondylitis.