Table 1.

International League of Associations for Rheumatology (ILAR) classification for Juvenile Idiopathic Arthritis (JIA)

Classification	Characteristics
Systemic arthritis	Arthritis in one or more joints, onset with fever, rash, or other systemic symptoms
Oligoarthritis	Arthritis affecting 1 to 4 joints for the first months of disease
Persistent oligoarthritis
Extended polyarticular
Polyarthritis	Arthritis affecting 5 or more joints in the first 6 months of disease; negative rheumatoid factor
Rheumatoid factor negative
Polyarthritis	Arthritis affecting 5 or more joints in the first 6 months of disease; positive rheumatoid factor
Rheumatoid factor positive
Psoriatic arthritis	Psoriasis in child or first degree relative, or dactylitis, nail pitting, oncholysis
Enthesitis-related arthritis	HLA-B27 related; formerly called spondylarthropathy
Undifferentiated arthritis	Arthritis that fulfills criteria in no categories or in 2 or more of the above categories

Derived from Petty 2004.