Juvenile Chronic Arthritis

Definition/diagnostic criteria Juvenile chronic arthritis, also known as juvenile idiopathic arthritis (JIA), is a condition characterised by persistent arthritis in one or more joints for at least six weeks, in children under the age of 16, with no identifiable cause. Diagnosis is largely clinical and requires exclusion of other conditions.

Epidemiology JIA is the most common type of arthritis in children, with an estimated incidence of around 1 in 10,000 children annually in the UK. The prevalence varies with the subtype of JIA and is more common in females, with a peak age of onset between 1-3 years for oligoarticular JIA, the most common subtype, and late childhood for polyarticular JIA and systemic JIA.

Diagnosis
Clinical features: Diagnosis of JIA is challenging due to the broad spectrum of symptoms and overlap with other paediatric conditions. Key clinical features include:

• Persistent joint swelling, pain and stiffness, particularly in the morning or after periods of inactivity.
• Systemic symptoms like fever, rash and lymphadenopathy may be present, especially in systemic JIA.

Investigations: No specific test confirms JIA, but investigations are crucial to exclude other conditions and assess disease severity. Typical investigations include:

• Full blood count, ESR and CRP to assess inflammation.
• Autoantibody tests (e.g. ANA, RF) to help subtype classification and predict prognosis.
• Imaging (X-ray, MRI, or ultrasound) to assess joint damage and inflammation.

Typical abnormalities might include elevated inflammatory markers, positive ANA in oligoarticular JIA, and evidence of joint effusion or synovitis on imaging.

Treatment Treatment aims to control symptoms, prevent joint damage and maintain function. It typically involves a combination of medication, physical therapy and, in some cases, surgery.

• Medication: NSAIDs are often first-line for mild symptoms, followed by disease-modifying anti-rheumatic drugs (DMARDs) like methotrexate for more severe cases. Biological agents (e.g. TNF inhibitors) are considered for refractory cases.
• Physical therapy: Essential for maintaining joint function and muscle strength.
• Surgical intervention: Required in cases with severe joint damage or deformities.

Prognosis The prognosis varies widely depending on the JIA subtype, disease severity at onset, and response to treatment. Oligoarticular JIA generally has a better prognosis, while polyarticular and systemic JIA can lead to significant disability. Early intervention and aggressive treatment are key to improving outcomes and preventing long-term disability.