Criteria

Category	Primary clinical criteria	Diagnostic exclusions
Systemic arthritis	Arthritis in one or more joints. Fever duration at least two weeks, quotidian pattern for three days. Requires one additional feature: Evanescent erythematous rash Generalized lymphadenopathy Hepatosplenomegaly Serositis	Psoriasis history. Human leukocyte antigen B27 positive male older than six years. Rheumatoid factor positivity.
Oligoarthritis	Affects one to four joints during first six months. Persistent subtype remains four or fewer joints. Extended subtype involves five or more joints after six months.	Psoriasis history. Human leukocyte antigen B27 positivity. Rheumatoid factor positivity. Systemic disease.
Polyarthritis (Rheumatoid factor negative)	Involves five or more joints during first six months. Rheumatoid factor tests negative.	Psoriasis history. Human leukocyte antigen B27 positivity. Systemic disease.
Polyarthritis (Rheumatoid factor positive)	Involves five or more joints during first six months. Two positive rheumatoid factor tests required. Tests performed at least three months apart.	Psoriasis history. Human leukocyte antigen B27 positivity. Systemic disease.
Psoriatic arthritis	Arthritis and psoriasis present. Alternatively, arthritis plus two features: Dactylitis Nail pitting or onycholysis Psoriasis in first-degree relative	Human leukocyte antigen B27 positivity. Rheumatoid factor positivity. Systemic disease.
Enthesitis-related arthritis	Arthritis and enthesitis present. Alternatively, arthritis or enthesitis plus two features: Sacroiliac joint tenderness Inflammatory lumbosacral pain Human leukocyte antigen B27 antigen Onset in male older than six years Acute anterior uveitis Relevant family history	Psoriasis history. Rheumatoid factor positivity. Systemic disease.
Undifferentiated arthritis	Fulfills criteria for no single category. Alternatively fulfills criteria for two or more categories.	None