Oligoarthritis
|
27%–60% of children with JIA. One to four joints are affected within 6 months of onset. The most commonly affected joint is the knee, followed by the ankle. ANA antibodies are identified in most patients and uveitis in approx. 20% of children |
Systemic arthritis
|
4%–20% of children with JIA. One or more joints are affected along with or preceded by at least 2 weeks of fever occurring daily for at least 3 days and with at least one of the following: transitional rash, generalized lymphadenopathy, hepato- or splenomegaly or serositis |
Polyarthritis (RF positive)
|
2%–7% of children with JIA. Five or more joints are affected within 6 months of onset, usually symmetric, small joints of the hands and feet, and with a positive RF test result. Large joints, like the knee, ankle, hip and shoulder, may also be inflamed at the beginning of the disease (approx. one third of patients) but alongside the inflammation of small joints. In approx. one third of patients, rheumatoid nodules are present. In this subtype, erosions are most frequent, seen in almost all children within the first 5 years of the disease |
Polyarthritis (RF negative)
|
11%–28% of children with JIA. Five or more joints, both small and large, can be affected within 6 months of onset, with two negative RF test results at least 3 months apart within 6 months of disease onset |
Psoriatic arthritis
|
2%–11% of children with JIA. Arthritis and psoriasis, or arthritis and two or more of the following features are present: dactylitis, nail pitting, oil drop sign or onycholysis, or psoriasis in a first-degree relative. In the first stage of the disease, synovitis usually occurs in the knee, ankle, and metatarsophalangeal joints. Initially, only few joints are affected (oligoarthritis) and later, more joints may be involved (asymmetric polyarthritis). There are very characteristic changes of the hand and foot joints (as in adults with PsA) |
Enthesitis-related arthritis (ERA)
|
5%–10% of children with JIA. Arthritis and enthesitis, or arthritis or enthesitis with two or more of the following features: the presence or a history of SIJ tenderness or IBP; a positive HLA-B27 antigen; male over 6 years of age at onset; acute anterior uveitis or a family history of ankylosing spondylitis, ERA, sacroiliitis with IBD, reactive spondyloarthritis, or acute anterior uveitis in a first degree relative. Mostly affects boys. The most typical sign is enthesitis. Often, there are also traits of oligo- or polyarthritis, including the hip and other lower limb joints. The disease may have a mild course, affecting ≤4 joints, but in 30%–40%, progression of the disease occurs to sacroiliitis and spondylitis |
Undifferentiated
|
Around 11%–21% of children with JIA that does not fit the criteria of any of the other categories |