HLA-B27

Key points

• HLA-B27 is a class I HLA surface antigen strongly associated with the seronegative spondyloarthropathies
• Conditions associated with HLA-B27: ankylosing spondylitis (~90% positive), reactive arthritis (~60–80% positive), psoriatic arthropathy, enteropathic arthritis (IBD-associated), acute anterior uveitis
• HLA-B27 positivity alone is not diagnostic — it is also found in ~10% of the general population — and is used to support, not confirm, a clinical diagnosis