Which HLA type is commonly associated with ankylosing spondylitis?

• A. HLA-B27
• B. HLA-DR4
• C. HLA-B8
• D. HLA-DR2

Answer: (A)

Genetic involvement is the key idea here: ankylosing spondylitis has a strong association with HLA-B27, a specific molecule in the immune system’s MHC class I group. Having HLA-B27 greatly increases the risk of developing the condition, and in many patients with ankylosing spondylitis this marker is present. It helps explain why the disease tends to run in families and why certain patterns of inflammation in the spine and sacroiliac joints occur. The presence of HLA-B27 is not absolute—not everyone with it will develop the disease, and some people with the disease may be HLA-B27 negative—yet it remains the most notable genetic association.

The other HLA types are linked with different autoimmune diseases, not the classic presentation of ankylosing spondylitis, so they are not the best clue for this condition.