Juvenile idiopathic arthritis — overview

Juvenile idiopathic arthritis (JIA) is the most common chronic inflammatory arthritis of childhood, defined as arthritis of unknown aetiology persisting for at least 6 weeks in a patient under 16 years of age. JIA is not a single disease but an umbrella term encompassing seven distinct subtypes classified by the International League of Associations for Rheumatology (ILAR), each with unique clinical features, genetic associations, disease course, and therapeutic implications. JIA is a leading cause of childhood disability and a major cause of preventable blindness (from uveitis). Early diagnosis and specialist-led management are essential to prevent joint damage, preserve function, and maintain quality of life.

JIA pathogenesis is heterogeneous across subtypes, reflecting distinct immunological mechanisms. Common to most subtypes is synovial inflammation driven by dysregulated innate and/or adaptive immunity, ultimately leading to joint damage if untreated.

Adaptive Immune-Driven Subtypes (Oligoarticular, RF-negative and RF-positive Polyarticular, Psoriatic)

• T cell dysregulation — CD4+ T helper cells (Th1 and Th17) drive synovial inflammation; regulatory T cell deficiency allows unchecked activation
• B cell involvement — autoantibody production (RF, anti-CCP in RF-positive polyarticular) promotes immune complex deposition and synovitis
• TNF-α, IL-6, IL-17 — key cytokines driving synovial proliferation and joint damage; targets for biologic therapy (TNF inhibitors, IL-6 blockade, IL-17 inhibition)
• ANA positivity — associated with uveitis risk (particularly in oligoarticular and psoriatic JIA); mechanism not fully elucidated

Innate Immune-Driven Subtypes (Systemic JIA)

• IL-1β and IL-18 — primary drivers of systemic JIA; autoinflammatory mechanism with macrophage and neutrophil activation; responds to IL-1 and IL-6 blockade
• Macrophage Activation Syndrome (MAS) — life-threatening complication of sJIA; uncontrolled macrophage and T cell activation leading to haemophagocytosis, cytopenias, coagulopathy, and multi-organ failure; IL-18 is markedly elevated
• Lung disease — a significant emerging complication of sJIA on IL-1/IL-6 inhibitors; mechanism under investigation (possibly drug-induced or disease-related eosinophilic/PAP-like lung disease)

Enthesitis-Related Arthritis (Spondyloarthropathy)

• HLA-B27 association — ~80% HLA-B27 positive; strong genetic predisposition shared with adult ankylosing spondylitis
• IL-17/IL-23 axis — key pathway for entheseal inflammation; rationale for IL-17 inhibitors (secukinumab)
• Anterior uveitis — acute, symptomatic (unlike the chronic asymptomatic uveitis of oligoarticular JIA)

The hallmark of JIA is persistent synovitis in a child under 16 years for at least 6 weeks. Clinical features vary substantially by subtype. Constitutional symptoms, fever, and rash suggest sJIA. Enthesitis and sacroiliac tenderness suggest ERA. Psoriasis or its stigmata suggest psoriatic JIA.

Core Features of Arthritis in Children

• Morning stiffness — often present as gelling (stiffness after inactivity); younger children may limp in the morning or refuse to walk; older children describe stiffness lasting >30 minutes
• Joint swelling — warm, swollen joints without erythema (erythema suggests septic arthritis); knee most commonly involved in oligoarticular JIA
• Pain — variable; younger children may not complain of pain but show functional limitation (refusing to use a limb, altered gait)
• Growth disturbance — local overgrowth (leg length discrepancy, macromelia) from hyperaemia; micrognathia from temporomandibular joint (TMJ) disease

Systemic JIA (sJIA) — Specific Features

• Quotidian (daily spiking) fever — characteristically spikes once or twice daily to >39°C, returns to baseline between spikes; fever may precede arthritis by weeks to months
• Evanescent salmon-pink rash — macular or maculopapular rash that appears with fever and fades; linear Koebner-type lesions possible
• Serositis — pericarditis, pleuritis; hepatosplenomegaly; lymphadenopathy
• MAS warning signs — sustained fever replacing quotidian pattern, falling ESR despite clinical deterioration, falling platelets, rising ferritin, liver dysfunction; urgent ICU review required

JIA is a clinical diagnosis. No laboratory test is pathognomonic. Investigations serve to exclude mimics (infection, malignancy, reactive arthritis), classify subtype, and assess inflammation.

• Essential
  FBC, ESR, CRP, ferritin

  FBC: normocytic anaemia of chronic disease; thrombocytosis in active JIA; cytopenias suggest MAS (falling platelets is an early MAS warning sign). ESR/CRP: elevated in active disease; in sJIA, ESR may be markedly elevated during fever but paradoxically falls in MAS. Ferritin >500 μg/L suggests sJIA; >10,000 μg/L strongly suggests MAS.
• Essential
  ANA (antinuclear antibody)

  ANA positivity (titre ≥1:40) is not diagnostic but stratifies uveitis risk. ANA+ oligoarticular JIA has highest uveitis risk and requires 3-monthly ophthalmology. ANA titre does NOT correlate with disease activity.
• Essential
  RF (rheumatoid factor) and anti-CCP

  Required for classification. RF-positive polyarticular JIA: RF positive on 2 occasions ≥3 months apart. Anti-CCP is more specific; combined RF+anti-CCP is equivalent to adult seropositive RA. Essential to obtain before biologic commencement.
• Essential
  HLA-B27

  Required for ERA classification and sacroiliitis risk stratification. Positive in ~80% of ERA; also in ~8% of general Australian population (background rate). Not diagnostic alone.
• Essential
  Joint X-rays

  Baseline for affected joints; assess for erosions, growth disturbance, joint space narrowing. Early disease may be normal. Periarticular osteopaenia and soft-tissue swelling are early signs. MRI superior for early erosions and sacroiliitis.
• Recommended
  Joint ultrasound

  Detects synovial hypertrophy and effusion; guides arthrocentesis. Particularly useful for hip involvement (difficult to assess clinically). Power Doppler detects active synovitis.
• Recommended
  MRI pelvis/sacroiliac joints

  Required in suspected ERA with sacroiliac involvement. Bone marrow oedema on STIR sequences confirms active sacroiliitis before structural changes are visible on plain films.
• Recommended
  Synovial fluid analysis

  Recommended for first presentation of monoarthritis to exclude septic arthritis (WBC >50,000/μL, positive culture). JIA: inflammatory fluid, WBC 5,000–50,000/μL, negative culture.

Risk stratification in JIA guides treatment intensity and monitoring frequency. Key stratification factors include disease subtype, joint count, inflammatory markers, ANA status, and presence of uveitis or MAS.

Uveitis Risk Stratification

• Highest uveitis risk — oligoarticular or psoriatic JIA + ANA positive + age at onset <6 years: slit-lamp examination every 3 months
• Moderate uveitis risk — oligoarticular or polyarticular JIA + ANA positive + age at onset 6–10 years: every 6 months
• Lower uveitis risk — ANA negative, or ERA (symptomatic acute uveitis), or age at onset >10 years: every 6–12 months
• Duration — continue ophthalmology surveillance for at least 5–7 years after diagnosis and until 5 years after disease remission

JIA management follows a treat-to-target approach with the goal of clinical remission (absence of active arthritis, uveitis, and systemic features). Treatment is subtype-specific. NSAIDs provide symptom relief but do not prevent joint damage. DMARDs (conventional and biologic) are the cornerstone of disease-modifying therapy.

Treatment should be tailored to JIA subtype given distinct pathophysiology and biologic targets.

Oligoarticular JIA

• NSAIDs (naproxen 10–15 mg/kg/day or ibuprofen 30–40 mg/kg/day) — first-line for mild disease; pseudo-porphyria with naproxen (photo-distributed blistering rash) requires cessation
• Intra-articular triamcinolone hexacetonide — highly effective for oligoarticular disease; response can last months to years; preferred over oral steroids; performed under GA in young children
• Methotrexate — for extended oligoarticular (≥5 joints by 6 months from onset) or NSAID/steroid-refractory disease

Polyarticular JIA (RF-positive and RF-negative)

• MTX first-line — 10–15 mg/m²/week; assess response at 3–6 months; combination with biologic if inadequate response
• TNF inhibitors (etanercept or adalimumab) — add if MTX fails; use adalimumab if uveitis present
• Abatacept — particularly for RF-positive polyarticular JIA; can be used as second biologic after TNF inhibitor failure

Systemic JIA (sJIA)

• NSAIDs — initial symptom management; insufficient for most; avoid NSAIDs as sole therapy in systemic JIA with macrophage activation syndrome risk
• IL-1 inhibition (anakinra, canakinumab) — first-line biologic; highly effective for fever and systemic features; often produces dramatic response within days
• IL-6 inhibition (tocilizumab) — alternative to IL-1 inhibition; particularly effective for arthritis component; monitor CRP carefully (suppressed by tocilizumab)
• MAS management — high-dose IV methylprednisolone (30 mg/kg/day ×3, max 1000 mg); high-dose anakinra (2–10 mg/kg/day); cyclosporin A (3–5 mg/kg/day); paediatric intensivist and haematology co-management

Enthesitis-Related Arthritis (ERA)

• NSAIDs — particularly effective for enthesitis and axial symptoms (indomethacin, naproxen)
• Sulfasalazine — first-line DMARD for peripheral joint disease in ERA; 30–50 mg/kg/day (max 2 g/day)
• TNF inhibitors — highly effective for refractory ERA and axial involvement; etanercept or adalimumab
• IL-17 inhibitors (secukinumab) — PBS-listed for ERA in Australia; particularly effective for axial involvement and enthesitis

JIA-Associated Uveitis

• Topical corticosteroids + mydriatics — initial management of active uveitis; taper by ophthalmologist
• MTX — systemic steroid-sparing agent for chronic uveitis; start early to prevent chronicity
• Adalimumab — PBS-listed for refractory JIA uveitis; superior to etanercept for ocular disease; continue for minimum 2 years after uveitis remission

Non-pharmacological management is integral to JIA care and should be provided alongside medications from diagnosis.

Physiotherapy and Occupational Therapy

• Physiotherapy — joint protection; range of motion exercises; hydrotherapy; muscle strengthening; gait re-education; foot orthotics for lower limb involvement
• Occupational therapy — splinting for wrist/hand involvement; adaptive equipment; school participation assessment; fatigue management
• Swimming and low-impact exercise — encouraged; contact sports should be individually assessed (risk of joint trauma)

Ophthalmology

• Regular slit-lamp examination — mandatory for ALL JIA patients; frequency determined by uveitis risk category (see Risk Stratification)
• Uveitis management — paediatric ophthalmologist with experience in JIA uveitis; topical and systemic therapy coordination with rheumatologist
• Band keratopathy, cataracts, glaucoma — late complications of uncontrolled uveitis requiring surgical management

Dental and Growth Monitoring

• Temporomandibular joint (TMJ) disease — common and under-recognised; referral to paediatric dental/maxillofacial if micrognathia or trismus; MRI of TMJ if clinically suspected
• Growth monitoring — corticosteroids and chronic inflammation impair linear growth; monitor height velocity 6-monthly; consider growth hormone consultation if growth failure
• Bone health — calcium and vitamin D supplementation for all children on chronic steroids; DEXA scan if prolonged steroid use; bisphosphonates in severe cases

School and Psychosocial Support

• School participation — school liaison letters; modified physical education; adjustments during flares (seating, writing aids, rest breaks)
• Psychological support — chronic disease in childhood affects mental health; screen for anxiety and depression; refer to psychologist or social worker as needed
• Family education — Arthritis Australia patient support resources; self-management programs

Monitoring in JIA must cover disease activity, treatment toxicity, growth, and uveitis surveillance. Frequency varies by disease activity, treatment, and subtype.

When to Refer Urgently

• MAS: Sustained fever replacing quotidian pattern + falling ESR + falling platelets + rising ferritin + liver dysfunction in sJIA patient — urgent PICU/paediatric rheumatology
• Septic arthritis: Hot, exquisitely tender single joint — exclude before commencing immunosuppression; orthopaedic and paediatric urgent review
• Active uveitis complications: Visual acuity change, photophobia, band keratopathy — urgent ophthalmology

Specific patient groups with JIA require tailored management strategies.

Adolescent Transition

• JIA persisting into adulthood — approximately 50–60% of JIA patients have active disease at age 18; transition to adult rheumatology services is a high-risk period for disease flare and loss to follow-up
• Transition planning — begin from age 14–16; education about self-management, medication, and adherence; joint paediatric/adult rheumatology clinics where available
• Contraception counselling — MTX is teratogenic; ensure adolescent females are aware of contraception requirements; adalimumab and biologics in pregnancy require specialist advice

Very Young Children (Toddlers <2 Years)

• JIA in toddlers is challenging — limping, refusing to walk, irritability, and refusal of use of a limb may be presenting features; high index of suspicion required
• Exclude malignancy (leukaemia) before confirming JIA — bone pain at night, cytopenias, and constitutional symptoms warrant bone marrow evaluation
• Intra-articular corticosteroids under GA — standard for oligo-articular disease in this age group

sJIA with Lung Disease

• Emerging concern — a subset of sJIA patients on IL-1/IL-6 inhibitors develop pulmonary alveolar proteinosis (PAP)-like lung disease or pulmonary hypertension; mechanism not fully understood
• Warning signs — persistent cough, desaturation, clubbing, peripheral eosinophilia in an sJIA patient on biologic therapy; chest CT and pulmonology referral

Stewardship in JIA focuses on appropriate use of biologics, steroid minimisation, vaccination management, and infection screening before immunosuppression.

GP Role in JIA Management

• Early recognition — persistent joint swelling or morning stiffness in a child for >6 weeks; refer urgently to paediatric rheumatology; do not initiate systemic corticosteroids without specialist review
• Monitoring — FBC and LFTs for MTX; blood pressure, glucose, growth for steroids; infection surveillance during biologics
• Vaccinations — annual influenza vaccine for all JIA patients; pneumococcal vaccine; avoid live vaccines if on biologics; coordinate with specialist team before any vaccination
• School liaison — GP can provide letters to support school accommodation (modified PE, rest breaks, seating adjustments) during active disease

JIA requires long-term multidisciplinary follow-up. Remission is possible but relapse is common; approximately 50% of patients have active disease into adulthood. A treat-to-target approach aiming for clinical remission (JADAS ≤ 1) optimises long-term outcomes.

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