Polyarticular onset juvenile idiopathic arthritis

Polyarticular JIA (poly-JIA) is defined as arthritis of five joints or more during the first 6 months of the disease.

• is the second most common JIA and accounts for 25% to 40% cases.
• prevalence is estimated to be
  • 40 per 100,000 children for RF-negative subtype
  • 10 per 100,000 children for RF-positive subtype
• more common among girls (1,2)

The condition is further divided into

• rheumatoid factor (RF) positive -
  • approximate frequency is between 2-10 %
  • more common in later childhood and adolescence
  • resembles the adult RF-positive rheumatoid arthritis
    • many paediatric rheumatologists consider this JIA subtype to be earlier-onset RA
• RF negative
  • approximate frequency is between 11-30 %
  • displays a biphasic trend with peaks of onset between 2 and 4 years and 6 and 12 years
  • several subgroups have been identified e.g. - resembling early-onset oligoarticular juvenile idiopathic arthritis, resembling adult-onset RF-negative rheumatoid arthritis etc (1,2,3)

The disease is characterised by the insidious (sometimes acute), onset of symmetric arthritis in five or more joints

• involve
  • both large and small joints
  • cervical spine - frequently
  • temparomandibular joints
• mild systemic features e.g. - low-grade fever, lymphadenopathy, and hepatosplenomegaly
• uveitis - an increased incidence is seen in RF-negative subgroup
• RF positive subtype patients are more likely to have symmetric small-joint arthritis, rheumatoid nodules, and early erosive synovitis with a chronic course (1,2,3)

Reference:

• (1) Barut K, Adrovic A, Şahin S, Kasapçopur Ö. Juvenile Idiopathic Arthritis. Balkan Medical Journal. 2017;34(2):90-101.
• (2) Kahn P.Juvenile idiopathic arthritis - an update on pharmacotherapy. Bull NYU Hosp Jt Dis. 2011;69(3):264-76.
• (3) Weinstein SL, Flynn JM. (2013). Juvenile Idiopathic Arthritis. Lovell and Winter’s Pediatric Orthopaedics (7th ed., pp. 348-368)