ILAR Classification Criteria for Juvenile Idiopathic Arthritis (JIA)

Juvenile idiopathic arthritis is a heterogeneous group of diseases characterised by arthritis of unknown origin with onset before age of 16 years.

International League of Associations for Rheumatology (ILAR) classification of juvenile idiopathic arthritis (JIA)

JIA can be diagnosed if age at onset is under 16 years, disease duration is 6 weeks or greater, and other known conditions are excluded.

• Systemic-onset JIA: Systemic arthritis is diagnosed if there is arthritis in 1 or more joints with, or preceded by, fever of at least 2 weeks' duration. Signs or symptoms must have been documented daily for at least 3 days and accompanied by 1 or more of the following: evanescent rash, generalised lymphadenopathy, hepato/splenomegaly, serositis. (Exclusions are A, B, C, and D from the exclusion list below.)
• Persistent or extended oligoarthritis: Oligoarthritis is diagnosed if there is arthritis affecting 1 to 4 joints during the first 6 months. Persistent oligoarthritis affects up to 4 joints throughout the course of the disease, and extended oligoarthritis affects more than 4 joints after the first 6 months of disease. (Exclusions are A, B, C, D, and E from the exclusion list below.)
• RF-negative polyarthritis: Polyarthritis (RF-negative) is diagnosed if there is rheumatoid factor (RF)-negative arthritis affecting 5 or more joints during the first 6 months of disease. (Exclusions are A, B, C, D, and E from the exclusion list below.)
• RF–positive polyarthritis: Polyarthritis (RF-positive) is diagnosed if there is RF-positive arthritis affecting 5 or more joints during the first 6 months of disease. Two or more RF tests (taken at least 3 months apart) are positive during the first 6 months of disease. (Exclusions are A, B, C, and E from the exclusion list below.)
• Psoriatic JIA: Psoriatic arthritis is diagnosed if there is arthritis and psoriasis, or arthritis and at least 2 of the following: dactylitis, nail pitting, onycholysis, and/or family history of psoriasis (in a first-degree relative). (Exclusions are B, C, D, and E from the exclusion list below.)
• Enthesitis-related arthritis: Enthesitis-related arthritis is diagnosed if there is arthritis and/or enthesitis with at least 2 of the following: presence or history of sacroiliac joint tenderness with or without inflammatory lumbosacral pain; presence of HLA B27 antigen; onset of arthritis in a male over 6 years of age; 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. (Exclusions are A, D, and E from the exclusion list below.)
• Undifferentiated: Undifferentiated arthritis is diagnosed if there is arthritis that does not fulfil criteria in any of the above categories or that fulfils criteria for 2 or more of the above categories.

Exclusions:

A. Psoriasis or history of psoriasis in patients or first-degree relatives.
B. Arthritis in HLA B27 positive males beginning after the age of 6 years.
C. Ankylosing spondylitis, enthesitis-related arthritis, sacroiliitis with inflammatory bowel disease, Reiter's syndrome, acute anterior uveitis, or history of  1 of these disorders in first-degree relatives.
D. Presence of IgM rheumatoid factor on at least 2 occasions at least 3 months apart.
E. Presence of systemic JIA in patients.

References:

1. Merino R, de Inocencio J, Garcia-Consuegra J. Evaluation of Revised International League of Associations for Rheumatology Classification Criteria for Juvenile Idiopathic Arthritis in Spanish Children (Edmonton 2001). J Rheumatol 2005;32:559-61. [Medline]
2. Petty RE, Southwood TR, Manners P, et al. International League of Associations for Rheumatology. International League of Associations for Rheumatology classification of juvenile idiopathic arthritis: second revision, Edmonton, 2001. J Rheumatol. 2004;31:390-392. [Medline]
3. Prakken B, Albani S, Martini A. Juvenile idiopathic arthritis. Lancet. 2011;377(9783):2138-2149. [Medline]