Seronegative spondyloarthropathies

Seronegative spondyloarthropathies include several chronic inflammatory arthritic diseases that affect the vertebral column. The most important diseases in this group are ankylosing spondylitis, reactive arthritis, and psoriatic arthritis. Common features include the absence of rheumatoid factor (RF) and a strong genetic association with HLA-B27. Spondyloarthropathies disproportionately affect men, with symptom onset generally occurring before the age of 45. The cardinal sign is slowly progressive pain in the lower back and sacroiliac joints (especially at night). Asymmetrical oligoarthritis and enthesopathy are also common. The diseases differ in the involvement of other organs, such as the eyes, the genitourinary tract (particularly in reactive arthritis) or the skin (particularly in psoriatic arthritis). Seronegative spondyloarthropathies usually respond well to NSAID therapy.

The different types of seronegative spondyloarthropathy do not necessarily represent distinct diseases but may overlap significantly in etiology, pathology, clinical features, and treatment.

• Ankylosing spondylitis (most common)
• Reactive arthritis
• Psoriatic arthritis
• Spondyloarthritis associated with inflammatory bowel disease (IBD)
• Undifferentiated spondyloarthropathy
• Peripheral spondyloarthritis
• Non-radiographic axial spondyloarthritis
• Juvenile spondyloarthritis

• Associations ^[1]
  • Negative for rheumatoid factor
  • Genetic association with HLA-B27
• Epidemiology
  • Generally more commonly affect men
  • Age of onset: typically between 20–40 years of age
• Clinical features ^[1]
  • Non-specific symptoms (fever, fatigue, weight loss)
  • Arthritis
    • Insidious, often unilateral onset
    • Particularly of the sacroiliac joints (especially for ankylosing spondylitis)
    • Asymmetrical peripheral oligoarthritis
    • Stiffness and pain is worse in the morning (typically > 30 minutes) and improves with movement
    • Usually responds well to NSAID therapy
  • Enthesitis or insertional tendinopathy (e.g., achillodynia)
  • Dactylitis: fingers have a sausage-like appearance
  • Extra-articular manifestations vary according to type, but involvement of the eye is common (e.g., iritis, iridocyclitis, uveitis)

• HLA-B27 is a surface antigen that belongs to the class I major histocompatibility complex (MHC class I). ^[2]
• HLA-B27 is strongly associated with seronegative spondyloarthropathies and other autoimmune conditions:
  • Ankylosing spondylitis: ∼ 90% ^[3]
  • Psoriatic arthritis: 10–25% ^[3][4]
  • Acute anterior uveitis: ∼ 50% ^[5][6]
  • IBD-associated ankylosing spondylitis: 25–78% ^[7]
  • Reactive arthritis 50–80% ^[8][9]

A-PAIR of conditions is commonly associated with HLA-B27: Ankylosing spondylitis, Psoriasis, Acute anterior uveitis, Inflammatory bowel disease, Reactive arthritis.