Juvenile idiopathic arthritis !

Long-lasting joint inflammation in children under 16 with no other cause. It can also inflame the eye silently, so regular eye checks are vital.

Updated 2026-11-01

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Why it happens

What it is

An umbrella term for chronic arthritis of unknown cause that begins before age 16 and lasts at least 6 weeks, after other causes have been excluded. It includes several subtypes with different patterns, from a few large joints to many small joints or a systemic form with fever and rash.

Who gets it

The most common chronic rheumatic disease of childhood. Oligoarticular disease predominates in young girls; polyarticular rheumatoid factor–positive disease resembles adult rheumatoid arthritis in adolescent girls; enthesitis-related arthritis is more common in older boys. Access to paediatric rheumatology and eye screening is uneven across Colombia and Latin America, which delays diagnosis.

Causes

Autoimmune and autoinflammatory mechanisms; cause unknown
Genetic susceptibility (HLA associations, such as HLA-B27 in enthesitis-related arthritis)
Possible environmental triggers such as infections

Risk factors

Female sex (oligoarticular and polyarticular types)
Early childhood onset (oligoarticular)
Positive ANA: higher risk of uveitis
HLA-B27 and family history of spondyloarthritis (enthesitis-related)
Personal or family history of psoriasis (psoriatic JIA)

Pathophysiology

Immune activation causes synovial inflammation with thickening (pannus), effusion and, if uncontrolled, erosion of cartilage and bone. Inflammation near growth plates can speed or slow growth, causing leg-length difference or a small jaw. In systemic JIA innate immune cytokines (IL-1, IL-6) drive fever, rash and serositis. Chronic anterior uveitis develops silently, especially in young ANA-positive girls.

Classification

Oligoarticular (1–4 joints in the first 6 months; persistent or extended)
Polyarticular rheumatoid factor–negative (5 or more joints)
Polyarticular rheumatoid factor–positive
Systemic JIA (quotidian fever, evanescent salmon rash, arthritis)
Enthesitis-related arthritis
Psoriatic arthritis and undifferentiated arthritis (ILAR classification)

Symptoms and signs

Joint swelling, warmth and reduced movement, often of the knee, ankle or wrist
Morning stiffness, limp or reluctance to walk after rest, rather than severe pain
Fever spiking once or twice a day with a salmon-pink rash that comes and goes (systemic form)
Enlarged lymph nodes, liver or spleen, or chest pain from serositis (systemic form)
Heel pain or low back pain from enthesitis (enthesitis-related)
Usually no eye symptoms despite uveitis; sometimes red eye or blurred vision

Diagnosis

Clinical: Diagnosis of exclusion: arthritis lasting at least 6 weeks with onset before 16 years and no other cause. The pattern and number of joints in the first 6 months define the subtype.
Tests: No single test confirms it. CBC, ESR/CRP, ANA (uveitis risk), rheumatoid factor and anti-CCP (prognosis), HLA-B27 when relevant; ferritin and clotting tests in systemic JIA. Joint fluid analysis when infection is suspected. Regular slit-lamp eye examinations screen for uveitis.
Imaging: Ultrasound and MRI show synovitis and effusion; plain radiographs exclude fractures and tumours and follow joint damage.

Differential diagnosis

Septic arthritis and osteomyelitis
Reactive arthritis and post-viral arthritis; Lyme disease where it occurs
Acute leukaemia and bone tumours
Systemic lupus erythematosus and other connective tissue diseases
Kawasaki disease and other causes of prolonged fever in children (for systemic JIA)
Trauma and orthopaedic conditions

Goal of treatment

Achieve inactive disease, protect joints and growth, prevent eye damage from uveitis, and allow normal school, play and development.

Treatment

Medical: NSAIDs for symptoms and intra-articular glucocorticoid injections for affected joints, especially in oligoarticular disease.
Medical: Methotrexate as the main conventional disease-modifying drug for persistent or polyarticular disease.
Medical: Biologics for disease not controlled or severe forms: TNF inhibitors, or IL-1 and IL-6 blockers for systemic JIA; systemic glucocorticoids short-term for severe systemic features.
Rehabilitation: Physiotherapy and occupational therapy to keep range of motion, strength and function; splints when needed; school and psychosocial support.
Follow-up: Ophthalmological screening with slit-lamp examination at intervals set by subtype and ANA status; monitoring of growth, blood counts, liver tests and infection risk on treatment; vaccinations updated before immunosuppression.

Drugs for this condition

Complications

Chronic anterior uveitis leading to cataract, glaucoma, band keratopathy and vision loss
Joint damage, contractures and disability
Growth disturbance: leg-length difference, small jaw (micrognathia), short stature
Macrophage activation syndrome in systemic JIA
Osteoporosis and infections related to treatment

Prognosis

Modern treatment allows most children to reach inactive disease, though many still have active arthritis into adulthood. Oligoarticular persistent disease has the best outlook; rheumatoid factor–positive polyarticular and systemic forms carry more risk of damage.

Test yourself

Think of the answer, then tap the question to see it.

What defines juvenile idiopathic arthritis?

Arthritis of unknown cause beginning before age 16 and lasting at least 6 weeks, after excluding other causes.

Which JIA patients have the highest risk of uveitis?

Young girls with oligoarticular disease and positive ANA.

Why do children with JIA need regular slit-lamp eye examinations?

Because chronic anterior uveitis is often painless and silent but can cause blindness if not detected.

What are the classic features of systemic JIA?

Daily spiking fever, an evanescent salmon-pink rash, arthritis, lymphadenopathy, organomegaly and serositis.

Which life-threatening complication can occur in systemic JIA?

Macrophage activation syndrome.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Juvenile idiopathic arthritis (MedlinePlus (U.S. National Library of Medicine), 2025).

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Representative model, for educational purposes only.

Joint capsule highlighted on the Durgical 3D model