25th February 2025

Overview of spondyloarthropathies

These are a heterogeneous group of seronegative inflammatory conditions, with common features including inflammation of the axial (spine) and peripheral joints, enthesitis (inflammation of tissue attaching ligaments and tendons to bone), a link to HLA-B27 and responsiveness to NSAIDs.

They include:

• Axial spondyloarthritis – ankylosing spondylitis (AS) when there is radiographic ankylosis (joint fusion)
• Psoriatic arthritis (PsA)
• Reactive arthritis 
• Enteropathic (inflammatory bowel disease) arthritis

They typically affect patients under 45, often with a delay in diagnosis. AS affects men twice as often, while the others have equal sex distribution. The prevalence of AS may be up to 0.23% in Caucasian populations, PsA in up to 10% with psoriasis and enteropathic arthritis in up to 15% with IBD. Some with PsA never get psoriasis.

Reactive arthritis occurs in up to 4% 1-4 weeks after certain gastrointestinal and genitourinary infections, including Chlamydia, Campylobacter, Salmonella, Shigella and Yersinia. The synovitis is sterile, so distinct from septic arthritis.

Up to 95% with AS and 30% with enteropathic arthritis have HLA-B27, which carries a 5 times higher risk of reactive arthritis. It may cause abnormal T-cell responses, interplaying with abnormal environmental exposure to microorganisms (through the skin in psoriasis and bowel in IBD).

AS and PsA are progressive, though can be relapsing and remitting. Reactive arthritis is of acute onset, with 70% recovering in 6 months. Enteropathic arthritis can improve with IBD remission.