The Onset, Evolution and Final Stages of Juvenile Ankylosing Spondylitis are Different from those of Adult Ankylosing Spondylitis

Juvenile-onset ankylosing spondylitis is a disease of unknown aetiology that affects primarily males under 16 years of age. It is characterized by early peripheral arthritis of the lower extremities and late onset inflammatory lumbar pain1–5. Of reported cases, 90% are B27 +1,5 and 20% have acute iridocyclitis3,4. These children are negative for rheumatoid factor and ANA. While sacroiliitis may be found as early as the first year, it may evolve as late as 12 years after onset of peripheral arthritis. Additional features include low-grade fever, family aggregation, and a benign evolution on long-term follow-up1,5–11.