Juvenile Idiopathic Arthritis

General features:

• •Joint swelling - the defining sign. Soft, boggy synovial swelling (NOT bony) that may be subtle early. Children often do NOT complain of pain - they accommodate. Parents may notice limp, reluctance to use a limb, avoidance of PE, or motor milestone regression (a toddler stops walking or insists on being carried).
• •Morning stiffness over 30 minutes and gelling after inactivity (sitting in class, car journeys). Younger children may not articulate stiffness; parents report the child is 'slow' or 'grumpy' in the morning, improving with movement.
• •Rapid muscle wasting (especially quadriceps around a swollen knee); joint contracture if untreated; growth disturbance (leg length discrepancy, micrognathia).

ILAR subtypes:

• •Oligoarticular JIA (most common, ~50-60%): 4 joints or fewer in the first 6 months. Knee is the single most commonly affected joint, then ankle. Persistent (remains 4 or fewer) vs extended (expands to 5 or more after 6 months - worse prognosis). ANA positive in ~70-80%. Peak onset 2-4 years; girls greater than boys (around 3:1). Classic presentation: a single swollen knee in a young girl. Highest chronic uveitis risk; asymptomatic anterior uveitis in up to 30%.

• •Polyarticular RF-negative (~20%): 5 or more joints, symmetric, RF negative. Any age. Moderate prognosis.

• •Polyarticular RF-positive (~5%): 5 or more joints, symmetric, RF positive (and often anti-CCP positive). Mirrors adult RA. Older adolescent girls. Aggressive and erosive - the WORST joint prognosis if not treated aggressively.

• •Systemic JIA (~10%, historically Still''s disease): quotidian (spiking daily) fever, classically late-afternoon/evening with return to normal between; evanescent salmon-pink macular rash (non-pruritic, appearing with fever and fading); lymphadenopathy; hepatosplenomegaly; serositis (pericarditis, pleuritis). Arthritis may develop weeks to months after systemic features. Very high CRP/ESR, leucocytosis, thrombocytosis, anaemia, and raised ferritin; ANA and RF typically negative. IL-1 and IL-6 driven. Macrophage activation syndrome (MAS) is the life-threatening complication: persistent non-remitting fever, FALLING WCC, platelets, and fibrinogen with RISING ferritin (often over 10,000 microg/L), coagulopathy, liver dysfunction, encephalopathy - emergency high-dose steroids, ciclosporin, anakinra.

• •Enthesitis-related arthritis (ERA, ~10%): older boys (onset over 6); HLA-B27 positive ~70-80%; enthesitis (Achilles, plantar fascia, tibial tuberosity, iliac crest) plus arthritis. Lower limb predominant and often asymmetric. Axial disease risk - sacroiliitis or spondylitis may develop and ERA may evolve into adult ankylosing spondylitis. Acute anterior uveitis may occur (symptomatic painful red eye).

• •Psoriatic JIA (~5%): arthritis with psoriasis, OR arthritis plus 2 of: dactylitis, nail pitting, first-degree relative with psoriasis. Arthritis may precede psoriasis by years; check nails and hidden skin areas.

• •Undifferentiated: does not fit, or fits more than one, category.

Common misdiagnoses to actively challenge: 'growing pains' (bilateral, nocturnal, no joint swelling - joint swelling is NEVER growing pains); hypermobility (does not produce persistent objective synovitis); trauma (a swollen joint attributed to trauma that does not resolve in 2 weeks needs re-evaluation); viral arthritis (self-limits within 6 weeks - persistence beyond meets the JIA definition).

JIA is a clinical diagnosis supported by investigations. There is no single diagnostic test. Normal inflammatory markers or absence of imaging confirmation do NOT exclude JIA - referral should not be delayed.

Blood tests:

• •FBC: anaemia, leucocytosis, thrombocytosis (systemic JIA). Pancytopenia with very high ferritin = MAS emergency. Leucopenia or blast cells suggest leukaemia - urgent blood film and haematology referral.
• •CRP and ESR: often raised in polyarticular and systemic JIA; may be NORMAL in oligoarticular JIA (a common clinical pitfall).
• •ANA: positive in ~70-80% of oligoarticular JIA. Stratifies uveitis risk. Does NOT diagnose JIA.
• •RF: positive in polyarticular RF-positive JIA - identifies the subtype with the worst joint prognosis.
• •Anti-CCP: may be positive in RF-positive polyarticular JIA; supports an erosive trajectory.
• •HLA-B27: positive in ~70-80% of ERA.
• •Ferritin: markedly elevated in systemic JIA; very high ferritin with falling WCC, platelets, and fibrinogen = MAS.
• •Blood film and LDH if leukaemia is suspected; renal and liver function as baseline; vitamin D for bone health.

Imaging:

• •Ultrasound: confirms synovitis (effusion, synovial thickening, power Doppler), guides aspiration, and monitors response. More sensitive than clinical examination for small effusions. JIA remains a clinical diagnosis and imaging should not delay referral.
• •Plain X-ray: may be normal early. Later shows periarticular osteopenia, joint space narrowing, erosions, and growth disturbance (epiphyseal overgrowth).
• •MRI: most comprehensive - synovitis, bone marrow oedema, cartilage damage, erosions, tenosynovitis, and growth plate changes. TMJ MRI with contrast is the gold standard for TMJ involvement (often clinically silent early).

Joint aspiration: essential to exclude septic arthritis in any child with an acutely hot, swollen joint - particularly with fever. Send for Gram stain, microscopy/cell count, and culture. Fever plus a hot swollen joint requires urgent aspiration, not routine JIA workup.

Other: bone marrow aspirate if leukaemia is suspected (must exclude leukaemia before systemic corticosteroids - steroids mask leukaemia). Echocardiography if pericarditis is suspected in systemic JIA. Risk-stratified slit-lamp ophthalmological surveillance is mandatory for all JIA patients per BSPAR/RCOphth guidelines - the schedule is determined by subtype, ANA status, age at onset, and disease duration; highest-risk children (oligoarticular, ANA-positive, onset under 7, first 4 years) are typically screened every 3-4 months initially.

Early aggressive treatment targeting remission. The 'window of opportunity' - intensive therapy before joint damage occurs - produces the best outcomes. UK practice follows BSR/BSPAR standards; key NICE technology appraisals are TA373 and TA238. Treatment is subtype-driven.

General principles:

• •Multidisciplinary team: paediatric rheumatologist (lead), specialist nurse, physiotherapy, OT, ophthalmology, psychology, podiatry, and school liaison.
• •Treat-to-target: aim for inactive disease or clinical remission; escalate if not achieved. Do NOT delay referral or treatment.

Pharmacological management by subtype:

Oligoarticular JIA:

• •Intra-articular corticosteroid injection - first-line; triamcinolone hexacetonide is preferred (longer-acting), often under image guidance with sedation or general anaesthesia in young children. Can induce remission lasting months to years.
• •Methotrexate if injections are insufficient (frequent relapses, extension to polyarticular pattern). Subcutaneous preferred in children (better bioavailability and less GI nausea). Once weekly with folic acid.

Polyarticular JIA:

• •Methotrexate is the first-line systemic DMARD; subcutaneous preferred. Start early.
• •Biologic therapy if methotrexate is inadequate (around 3-6 months): anti-TNF (etanercept, adalimumab) is the usual first-line biologic (NICE TA373); anti-IL-6 (tocilizumab) is an alternative; abatacept (T-cell co-stimulation blockade) is used after biologic failure (NICE TA373). RF-positive polyarticular JIA often requires early biologic escalation.

Systemic JIA (IL-1/IL-6 driven, NOT primarily TNF):

• •NSAIDs for mild initial symptoms; corticosteroids short-term for moderate-severe systemic features (exclude leukaemia first).
• •Anti-IL-1 (anakinra daily subcutaneously, canakinumab monthly) and anti-IL-6 (tocilizumab; NICE TA238) - the targeted biologics for systemic JIA. Anti-TNF agents are generally LESS effective.
• •MAS: high-dose IV methylprednisolone, ciclosporin, anakinra; haematology input; ICU may be needed.

Enthesitis-related arthritis: NSAIDs may help symptoms; conventional DMARDs (sulfasalazine, methotrexate) may help peripheral arthritis but do NOT treat axial disease; anti-TNF (etanercept, adalimumab) for persistent disease, especially with sacroiliitis or axial involvement (NICE TA373).

Psoriatic JIA: methotrexate (also treats skin); anti-TNF biologics for inadequate response.

Uveitis: topical corticosteroid eye drops first-line for active disease; methotrexate as steroid-sparing for chronic or recurrent uveitis; adalimumab is the biologic of choice for refractory JIA-associated uveitis (NICE TA373; supported by the SYCAMORE trial). More effective for uveitis than etanercept.

Prescribing considerations: live vaccines are CONTRAINDICATED in children on methotrexate or biologic therapy (MMR, BCG, yellow fever, oral polio, live attenuated intranasal influenza). Inactivated vaccines are safe and encouraged. Methotrexate monitoring requires regular FBC, LFTs, and U&Es.

Rehabilitation is essential alongside pharmacological therapy. Goals: maintain joint function, prevent contracture, optimise physical development, support school participation, and promote wellbeing.

Physiotherapy: maintain and restore range of motion - particularly joints prone to contracture (knee, wrist); active and active-assisted exercises (do NOT immobilise, which causes contracture and wasting). Progressive strengthening once acute inflammation is controlled; rapid muscle wasting occurs around inflamed joints. Hydrotherapy is excellent - warm water reduces stiffness, buoyancy reduces loading, and engagement is high in children. Exercise and sport are SAFE and BENEFICIAL - PE and sport with appropriate modifications during flares. Swimming, cycling, and walking are well tolerated.

Occupational therapy: hand and wrist function, splinting, school adaptations (pen grips, IT access), joint protection, energy conservation.

Podiatry, psychological support, and school liaison are essential. The Children''s Chronic Arthritis Association (CCAA) and Versus Arthritis provide peer support.

Transition to adult services: structured transition from paediatric to adult rheumatology per NICE NG43 - typically begins at 14-16 and completes by 18-19, with a designated coordinator and developmentally appropriate planning.

• •ILAR JIA classification (2001 Edmonton revision) - the 7-subtype framework that continues to dominate UK clinical and exam usage; PRINTO-led re-classification work is evolving.
• •NICE TA373 - abatacept, adalimumab, etanercept, and tocilizumab for polyarticular JIA.
• •NICE TA238 - tocilizumab for systemic JIA.
• •BSPAR/RCOphth uveitis screening guidelines - risk-stratified slit-lamp surveillance schedule by subtype, ANA, age at onset, and disease duration.
• •SYCAMORE trial - adalimumab for refractory JIA-associated uveitis; underpins NICE TA373 uveitis recommendations.
• •NICE NG43 - transition from children''s to adults'' services.

• •JIA: chronic arthritis 6+ weeks, onset under 16, no other cause; ILAR 7-subtype classification.
• •Oligoarticular is most common (~50%); ANA+ identifies highest chronic uveitis risk.
• •Polyarticular RF-positive carries the worst joint prognosis; mirrors adult RA.
• •Systemic JIA: quotidian fever + salmon-pink rash; IL-1/IL-6 driven; MAS is the emergency complication.
• •Adalimumab is the biologic of choice for refractory JIA-associated uveitis (SYCAMORE; NICE TA373).
• •Live vaccines are contraindicated on methotrexate or biologic therapy; inactivated vaccines are safe.