Whereas the subtypes HLA-B*27:05, -:04, and -:02 are associated with ankylosing spondylitis, HLA-B*27:06 and HLA-B*27:09 are not, despite HLA-B*27:05 and 27:09 differing by one amino acid (26). The gene discussed is HLA-B; the disease is ankylosing spondylitis.