HLA-B27 is a major histocompatibility class I (MHC-I) molecule that plays a role in antigen presentation. It is well known for its strong association with ankylosing spondylitis (AS), a link discovered more than 40 years ago. HLA-B27 positivity in the white population carries a 20-fold increased risk of developing spondyloarthritis (SpA)1. Prevalence of AS mirrors the HLA-B27 prevalence across the world, with the highest prevalence of HLA-B27 reported in Haida Indians at 50% to Japan at 0.1%. At the time of this publication at least 132 subtypes of HLA-B27 have been identified according to the Immuno Polymorphism Database2. The prevalence of HLA-B27 in the white population is around 6% to 8%, with HLA-B*2705 being the predominant subtype.
HLA-B27 is present in 85% of white patients with AS. However, less than 5% of HLA-B27–positive people ever develop AS. Apart from AS, other diseases associated with HLA-B27 are uveitis, psoriatic arthritis, and lone aortic regurgitation. Patients with HLA-B27 have a survival advantage with human immunodeficiency virus (HIV) and hepatitis C virus infection. It is thought to be due to the presence of virus-specific peptides on HLA-B27 that are recognized by protective CD8+ T cells3. There is a latitude-dependent difference in the distribution of HLA-B27, with higher latitudes including the …
Address correspondence to Dr. N. Haroon, 1E-425, 399 Bathurst St., Toronto Western Hospital, Toronto M5T 2S8, Ontario, Canada. E-mail: nigil.haroon{at}uhn.ca