a description of jra (from NYU)

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Juvenile rheumatoid arthritis, known as juvenile chronic arthritis in Europe, is the most common rheumatic disease in children. Criteria for diagnosis include age of onset less than 16 years, disease duration greater than six weeks, arthritis, and exclusion of other forms of juvenile arthritis. Juvenile rheumatoid arthritis is subdivided into pauciarticular (less than five joints involved), polyarticular (five or greater joints involved), and systemic (arthritis, fever and rash) forms.

Skin manifestations of juvenile rheumatoid arthritis include amyloiosis which occurs in one to ten percent of all subtypes. Ninety percent of systemic-onset juvenile rheumatoid arthritis is characterized by an evanescent salmon-covered eruption that occurs on the trunk and thighs and which is concurrent with fever. The eruption may be elicited by scratching, ie, the Koebner phenomenon. A variant of juvenile rheumatoid arthritis with onset in young adulthood is adult Still's disease, which occurs at ages 16 to 35, is characterized by multi-system involvement and an evanescent, salmon-pink, macular and papular eruption, and is accompanied by fever. The eruption occurs on the trunk and proximal extremities and may be elicited by the Koebner phenomenon.

The skin manifestations of rheumatoid arthritis include rheumatoid nodules, rheumatoid papules, rheumatoid neutrophilic dermatitis, and vasculitis. Rheumatoid nodules are subcutaneous nodules that occur in 20 percent of rheumatoid patients with positive rheumatoid factors, and rarely in seronegative patients. The nodules generally correlate with disease activity. Rheumatoid nodulosis (multiple, widespread nodules) is a separate entity that occurs mostly in men with a low-grade fever and mild synovitis. Nodules develop most commonly on pressure areas, such as the elbows, joints, ischial and sacral prominences, along tendons, and the occiput. In general, nodules regress with treatment as the rheumatoid arthritis improves. Rheumatoid nodules in rheumatoid factor-negative patients have been reported but appear to be rare.

References:

Kaye BR, et al. Rheumatoid nodules: review of the spectrum of associated conditions and proposal of a new classification, with a report of four seronegative cases. Am J Med 76:279, 1984

Yamamoto T, et al. Skin manifestations associated with rheumatoid arthritis. J Dermatol 22:324, 1995

JL, Ostensen M. Pregnancy and rheumatoid arthritis. Rheum Dis Clin North Am 23:195, 1997

White PH. Juvenile chronic arthritis: clinical features. In: Klippel JH, Dieppe PA, eds. Rheumatology, 2nd Ed. Mosby, London, 1998 http://www.med.nyu.edu/Derm/conf/022001-7.html