JIA classification
Juvenile Idiopathic Arthritis (JIA) is a diagnosis of exclusion. It describes a group of conditions characterised by persistent arthritis lasting at least 6 weeks, with onset before 16 years of age, and no identifiable cause. The underlying cause is likely to involve a combination of genetic and environmental factors, although JIA is rarely familial.
JIA is classified according to the pattern of disease at onset, particularly the number of joints involved in the first 6 months, and the presence or absence of rheumatoid factor. Understanding the subtype is important, as it guides monitoring and management.
|
Subtype |
Key Features |
|
Systemic JIA |
Arthritis with systemic features such as fever, rash, lymphadenopathy and serositis. |
|
Oligoarthritis |
1–4 joints in first 6 months. |
|
Polyarthritis |
≥5 joints in first 6 months. |
|
Enthesitis-related arthritis (ERA) |
Arthritis and enthesitis, or arthritis/enthesitis plus ≥2 of: |
|
Psoriatic arthritis |
Arthritis with psoriasis, or arthritis plus ≥2 of: |
|
Undifferentiated arthritis |
Does not meet criteria for a single category or meets criteria for more than one subtype. |
