Spondyloarthropathy

Spondyloarthropathies are a group of related inflammatory joint disease associated with the MHC class I molecule HLA-B27. Subgroups (with increased HLA-B27 frequency) are:

• ankylosing spondylitis (AS, 90%),
• reactive arthritis (ReA)/Reiter's syndrome (RS, 80%),
• enteropathic arthritis associated with inflammatory bowel disease (IBD, 70%),
• Psoriatic arthritis (60%),
• isolated acute anterior uveitis (AAU, iritis or iridocyclitis, 50%), and
• undifferentiated SpA (USpA, 20–25%).

Whipple disease and Behçet disease may also be linked to HLA-B27, as may undifferentiated spondyloarthropathy.