How is the HLA-B27 gene variation associated with ankylosing spondylitis and Reiter syndrome?

The HLA-B27 gene variation is a significant genetic factor associated with a group of conditions known as spondyloarthropathies, including ankylosing spondylitis and Reiter syndrome (also known as reactive arthritis).1

• Ankylosing Spondylitis: This condition shows a very strong genetic link, with more than 90 percent of white patients of western European descent who have the disease testing positive for the HLA-B27 gene variant.1
• Reiter Syndrome: This disorder is also strongly associated with the HLA-B27 variant, which is present in 65 to 96 percent of symptomatic individuals. In those who carry this gene, symptoms of reactive arthritis may appear more suddenly and tend to be more severe than in individuals who are HLA-B27-negative.12

While the exact mechanisms remain under study, these conditions are thought to involve an aberrant immune response, often triggered by infections outside the joint, such as gastrointestinal or sexually transmitted diseases. The presence of HLA-B27 serves as a key predisposing factor for these inflammatory joint diseases.12