HLA-B27

A class I human leukocyte antigen encoded within the major histocompatibility complex (MHC) on chromosome 6, associated with an increased genetic susceptibility to several autoimmune and inflammatory disorders, particularly those affecting the joints, spine, and eyes.

Causes of a positive test

• Autoimmune and inflammatory disorders

  • Ankylosing spondylitis

  • Reactive arthritis

  • Acute anterior uveitis (iritis)

  • Psoriatic arthritis

  • Enteropathic arthritis associated with inflammatory bowel disease

• Other associated conditions

  • Undifferentiated spondyloarthritis

  • Juvenile idiopathic arthritis (enthesitis-related subtype)

• Healthy individuals without autoimmune disease (genetic carrier state)