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Polyarticular JRA

- See: juvenile RA menu

- Discussion:
    - definition: > 5 involved joints;
    - large and small joint may be affected;
    - accounts for about 50% of patients w/ JRA;
    - may occur at 1-3 yrs or during early adolescence (after age 10);
    - children w/ seronegative arthritis usually present before age 5 years and have iridocyclitis if fewer than five joints are involved;
    - destruction of joints is less severe than that of seropositive pts, who present after age 10 and have adult-like disease progression;
    - differential dx
    - prognosis:
           - generally good: 60% of pts in remission after 15 yrs, however, large subset will develop cripling arthritis;
           - severe hip disease is a major late disability.
           - leg length inequality may occur (either larger or smaller)
           - usually occurs w/ knee involvment;

- Labs:
    - ANA: positive in 30%;
    - RF is usually negative in child, but may be pos. in adolescent;
         - w/ positive RF, more likely to have rheumatoid nodules, joint erosions, & Felty's syndrome (RA, splenomegaly, & leukopenia);

- Radiographs:
    - osteopenia and early ossification of carpal bones visible on radiographs;
    - distal ulnar physis matures early, & short ulna leads to ulnar translocation;

- Clinical Presentation:
    - frequently, there is symmetric involvement of knees, wrists, & ankles;
    - may also have involvment of cervical spine (60 %), hips, shoulder & TMJ.
    - cervial spine Involvement: common at C2-3;
    - constitutional symptoms:
    - growth retardation, low grade fever, mild organomegaly, adenopathy, and anemia;
    - chronic iridocyclitis is less common than in pauciarticular JRA;
    - Upper Extremity- Hands and Wrist:
         - hands:
                - PIP and MP joints are involved in approx. 20% of pts;
                - swan neck deformity: responds to use of a splint;
                - boutonniere deformity:
         - wrist:
                - forces of usage are contributory, accounting for fact that children, w/ no work demands, have less ulnar drift than do adults;

- Treatment:
    - in the study by Lovell DJ, et al (2000), the authors evaluated the safety and efficacy of etanercept, a soluble tumor necrosis factor  receptor (p75):Fc fusion
            protein, in children with polyarticular juvenile rheumatoid arthritis who did not tolerate or had an inadequate response to methotrexate;
            - patients 4-17 years received 0.4 mg of etanercept per kg of body wt subQ twice weekly for up to 3 months in the initial, open-label part of a multicenter trial;
            - at the end of the open-label study, 51 of the 69 patients (74 %) had had responses to etanercept treatment;
            - in the double-blind study, 21 of the 26 patients who received placebo (81 percent) withdrew because of disease flare, as compared
                    with 7 of the 25 patients who received etanercept (28 percent) (P=0.003).
             - Etanercept in children with polyarticular juvenile rheumatoid arthritis. Pediatric Rheumatology Collaborative Study Group. 

Radiographic changes in juvenile chronic polyarthritis.