ILAR Classification of Juvenile Idiopathic Arthritis

Juvenile idiopathic arthritis (JIA) is an umbrella term for a group of abnormalities characterized by chronic articular inflammation and association with HLA alleles. The International League Against Rheumatism (ILAR) has classified JIA into seven subtypes, including an unclassifiable group. These include:

• Systemic arthritis: Arthritis in one or more joints with or preceded by fever of at least 2 weeks' duration documented to be daily for at least 3 days, and accompanied by one or more of: evanescent erythematous rash, lymphadenopathy, hepatomegalyor splenomegaly, or both, serositis
• Oligoarthritis: Arthritis in 4 or fewer joints in the first 6 months. Subtypes include persistent (no more than 4 joints throughout the course of the disease) and extended (more than 4 joints after the first 6 months).
• Polyarthritis, RF negative: Arthritis affecting 5 or more joints in the first 6 months of disease. RF is negative
• Polyarthritis, RF positive: Arthritis affecting 5 or more joints in the first 6 months of disease. Two or more tests for RF, conducted at least 3 months apart during the first 6 months, are positive. Considered the pediatric version of adult rheumatoid arthritis.
• Psoriatic: Arthritis plus psoriasis OR Arthritis plus at least two of the following: dactylitis, nail pitting or onycholysis, psoriasis in a first-degree relative.
• Enthesis-related: Arthritis plus enthesitis OR Arthritis or enthesitis, plus at least two of the following: presence of or a history of sacroiliac joint tenderness and/or 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 AS, ERA, sacroiliitis with IBD, reactive arthritis, or acute anterior uveitis in a first-degree relative
• Unclassified: Arthritis that fulfills criteria in none of the above categories, or fulfills criteria in two or more of the above categories

References

Petty RE, Southwood TR, Baum J, Bhettay E, Glass DN, Manners P, Maldonado-Cocco J, Suarez-Almazor M, Orozco-Alcala J, Prieur AM. Revision of the proposed classification criteria for juvenile idiopathic arthritis: Durban, 1997. J Rheumatol. 1998 Oct;25(10):1991-4.