What HLA type is associated with ankylosing spondylitis?

Ankylosing spondylitis is a type of inflammatory arthritis that primarily affects the spine and the sacroiliac joints. It is known to have a strong genetic component, and the HLA-B27 antigen is notably associated with the disease. More than 90% of individuals with ankylosing spondylitis express the HLA-B27 antigen, making it a key marker in the diagnosis and understanding of the condition.

The presence of HLA-B27 suggests an increased risk of developing ankylosing spondylitis but does not necessarily mean that someone with this antigen will develop the disease, as not everyone who is HLA-B27 positive has ankylosing spondylitis. Its role in the pathogenesis is believed to be related to how the immune system responds to certain triggers, which may include bacterial infections or other environmental factors.

In contrast, HLA-DR4, HLA-A1, and HLA-Cw6 are associated with other autoimmune conditions but not specifically linked to ankylosing spondylitis. HLA-DR4 is often associated with rheumatoid arthritis, HLA-A1 is linked to other types of spondyloarthropathies, and HLA-Cw6 is associated