ANA, Antinuclear antibody; RA, rheumatoid arthritis; RF, rheumatoid factor.
Figure 89-1 An affected knee in a patient with oligoarticular juve-nile idiopathic arthritis. Note sizeable effusion, bony proliferation, and flexion contracture.
presence of an active growth plate, it may be possible to findbony abnormalities of the surrounding bone, causing bonyproliferation and localized growth disturbance. In a lowerextremity joint, a leg length discrepancy may be appreciable ifthe arthritis is asymmetric.
All children with chronic arthritis are at risk for chronic iridocyclitis or uveitis. There is an association between human leukocyte antigens (HLAs) (HLA-DR5, HLA-DR6, and HLA-DR8) and uveitis. The presence of a positive antinuclear antibody identifies children with arthritis who are at higher risk for chronic uveitis. Although all children with JIA are at increased risk, the subgroup of children, particularly young girls, with oligoarticular (less than five affected joints) JIA and a positive antinuclear antibody are at highest risk, with an incidence of uveitis of 80%. The uveitis associated with JIA can be asymptomatic until the point of visual loss, making it a primary treatable cause of blindness in children. It is crucial for children with JIA to undergo regular ophthalmologic screening with a slit-lamp examination to identify anterior chamber inflammation and to initiate prompt treatment of any active disease.
Oligoarticular JIA is defined as the presence of arthritis in fewer than five joints within 6 months of diagnosis. This is the most common form of JIA, accounting for approximately 50% of cases.
Oligoarticular JIA presents in young children, with a peak at 1 to 3 years and another peak at 8 to 12 years. The arthritis is found in medium-sized to large joints; the knee is the most common joint involved, followed by the ankle and the wrist. It is unusual for small joints, such as the fingers or toes, to be involved, although this may occur. Neck and hip involvement also is uncommon. Children with oligoarticular JIA may be otherwise well without any evidence of systemic inflammation (fever, weight loss, or failure to thrive) or any laboratory evidence of systemic inflammation (elevated white blood cell count or erythrocyte sedimentation rate). A subset of these children later develops polyarticular disease (called extended oligoarthritis).
Polyarticular JIA describes children with arthritis in five or more joints within the first 6 months of diagnosis and accounts for about 40% of cases. Children with polyarticular JIA tend to have symmetric arthritis, which can affect any joint but typically involves the small joints of the hands, feet, ankles, wrists, and knees. The cervical spine can be involved, leading
Extra-articular manifestations Systemic symptoms Enthesopathy Psoriasis, nail Bowel symptoms (systemic-onset JRA)
ANA, Antinuclear antibody; IBD, inflammatory bowel disease; JAS, juvenile ankylosing spondylitis; JIA, juvenile idiopathic arthritis;
PSA, poststreptococcal arthritis; RF, rheumatoid factor.
to fusion of the spine over time. In contrast to oligoarticular JIA, children with polyarticular disease can present with evidence of systemic inflammation, including malaise, low-grade fever, growth retardation, anemia of chronic disease, and elevated markers of inflammation. Polyarticular JIA can present at any age, although there is a peak in early childhood. There is a second peak in adolescence, but these children differ by the presence of a positive rheumatoid factor (and anti-CCP antibody) and most likely represent a subgroup with true adult rheumatoid arthritis; the clinical course and prognosis are similar to the adult entity.