Table 1

ILAR Classicfication Criteria for juvenile idiopathic arthritis

ILAR categoryFrequencyDefinition
Systemic JIA5%–15%Arthritis in 1 or more joints with or preceded by fever of at least 2-week duration, documented to be daily for at least 3 days, and accompanied by 1 or more of the following:

  • Evanescent erythematous rash

  • Generalised lymphadenopathy

  • Hepatomegaly and/or splenomegaly

  • Serositis

Oligoarticular JIA30%–60%Arthritis affecting 1–4 joints during the first 6 months of the disease
2 subcategories recognised:

  1. Persistent oligoarthritis: affecting not more than 4 joints throughout the disease course

  2. Extended oligoarthritis: affecting a total of more than 4 joints after the first 6 months of the disease

Rheumatoid factor positive polyarticular JIA3%–7%Arthritis affecting 5 or more joints during the first 6 months of disease with 2 or more positive tests for rheumatoid factor at least 3 months apart during the first 6 months of the disease
Rheumatoid factor negative polyarticular JIA10%–25%Arthritis affecting 5 or more joints during the first 6 months of disease with a negative rheumatoid factor test
Enthesitis-related JIA5%–10%Arthritis and/or enthesitis (sites where tendons or ligaments insert into the bone) with at least 2 of the following:

  • The presence or history of sacroiliac joint tenderness and/or inflammatory lumbosacral pain

  • HLA-B27 antigen positive

  • Onset in a boy over the age of 6 years

  • Acute (symptomatic) anterior uveitis

  • History of ankylosing spondylitis, enthesitis-related arthritis, sacroiliitis with inflammatory bowel disease, Reiter’s syndrome or acute anterior uveitis in a first-degree relative

Psoriatic JIA3%–10%Arthritis and psoriasis or arthritis and at least 2 of the following:

  • Dactylitis

  • Nail pitting/onycholysis

  • Psoriasis in a first-degree relative

Undifferentiated JIA10%–20%Arthritis that fulfils criteria in no category or in 2 or more of the above categories

  • HLA, human leucocyte antigen; ILAR, International League Against Rheumatism; JIA, juvenile idiopathic arthritis.