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Juvenile idiopathic arthritis

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"juvenile idiopathic arthritis"[MeSH Terms]

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"juvenile idiopathic arthritis" treatment

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juvenile idiopathic arthritis joint swelling rash

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Juvenile Idiopathic Arthritis (JIA)

JIA is the most common rheumatologic condition in children and serves as an umbrella term replacing the older "juvenile rheumatoid arthritis." It encompasses a heterogeneous group of arthritides of unknown cause — likely autoimmune — that present before age 16 with arthritis persisting ≥6 weeks after other causes are excluded.

Classification Criteria (ILAR)

CriterionRequirement
Age of onset< 16 years
Duration≥ 6 weeks
DefinitionJoint swelling, limitation in ROM, and/or tenderness

Subtypes (ILAR Classification)

1. Oligoarticular JIA (40–50% — most common)

  • Demographics: F > M; peak onset 2–4 years
  • Joints: 1–4 joints in first 6 months; lower extremity large joints (knees, ankles)
  • Subtypes: Persistent (<4 joints throughout) vs. Extended (>4 joints after 6 months)
  • Key features: 60–70% ANA positive; uveitis in ~30% (16% persistent, 25% extended)

2. Polyarticular RF-negative (20–35%)

  • Demographics: F > M; bimodal peak 2–4 and 10–14 years
  • Joints: ≥5 joints (first 6 months); small and large, symmetric or asymmetric
  • Key features: 50% ANA positive; uveitis prevalence 4%

3. Polyarticular RF-positive (<10%)

  • Demographics: F > M; peak onset 9–12 years
  • Joints: ≥5 joints; symmetric polyarthritis
  • Key features: 40% ANA positive; rheumatoid nodules; uveitis 2%
  • Closest analog to adult RA

4. Systemic JIA / Still Disease (5–15%)

  • Demographics: M = F; peak 1–5 years
  • Definition: Arthritis + quotidian (daily spiking) fevers ≥2 weeks, plus ≥1 of:
    • Evanescent salmon-pink macular rash (non-pruritic, on trunk, extremities, palms/soles)
    • Generalized lymphadenopathy
    • Hepatosplenomegaly
    • Serositis (pleuritis, pericarditis)
  • Labs: Anemia, leukocytosis, thrombocytosis, elevated ESR/CRP/ferritin; ANA 20%; HLA-B27 5–10%
  • Fevers characteristically spike to ≥39°C in a "rabbit-ear" diurnal pattern
  • Uveitis rare (1%)

5. Enthesitis-Related Arthritis (10–15%)

  • Demographics: M > F; peak 9–16 years
  • Peripheral arthritis + enthesitis; sacroiliac involvement common
  • Strongly HLA-B27 associated; overlaps with spondyloarthropathy spectrum

6. Psoriatic JIA

  • Arthritis + psoriasis, or arthritis + ≥2 of: dactylitis, nail pitting/onycholysis, first-degree relative with psoriasis

7. Undifferentiated (5%)

  • Does not fit any subtype, or meets criteria for ≥2 subtypes

Clinical Features

Joints: Knee most commonly affected; wrist (flexed/ulnar deviated), hands (radially deviated), cervical spine, and TMJ can all be involved.
Extra-articular:
  • Uveitis — most common in oligoarticular ANA-positive girls; often asymptomatic → requires routine slit-lamp exam every 3–6 months
  • Cervical spine involvement → facet ankylosis, atlantoaxial subluxation, kyphosis
  • Lower extremity: flexion contractures (hip, knee), subluxation, equinovarus feet, valgus knees
Radiology: Early — soft tissue swelling and effusion; Late — bone and cartilage destruction

Macrophage Activation Syndrome (MAS)

A life-threatening complication occurring in 7–17% of systemic JIA patients (can also complicate SLE, Kawasaki disease).
FeatureDescription
MechanismUncontrolled T-lymphocyte and macrophage proliferation → cytokine storm → multiorgan failure
ClinicalPersistent fever, altered mental status, lymphadenopathy, hepatosplenomegaly, purpura, mucosal bleeding
LabsPancytopenia, liver dysfunction, DIC, hyperferritinemia, hypertriglyceridemia, low fibrinogen, paradoxical drop in ESR (despite active inflammation)
TreatmentPulse IV corticosteroids + IL-1 or IL-6 blockade; cyclosporine A or JAK inhibitors for refractory disease

Treatment

Treatment is subtype- and severity-dependent, with a step-up approach:
CategoryAgents
NSAIDsNaproxen, ibuprofen — first-line for mild disease
CorticosteroidsIntra-articular injections preferred; systemic for severe/systemic disease
DMARDs (non-biologic)Methotrexate (current first-line DMARD), leflunomide, azathioprine
Biologic — anti-TNFEtanercept, infliximab, adalimumab
Biologic — anti-IL-1Anakinra, canakinumab (especially for systemic JIA)
Biologic — anti-IL-6Tocilizumab (systemic and polyarticular JIA)
T-cell costimulation inhibitorAbatacept
Anti-CD20Rituximab
JAK inhibitorsTofacitinib, baricitinib (newer option)
SurgicalSynovectomy (refractory), arthrodesis, arthroplasty (severe disease)
Methotrexate is the standard first-line DMARD; biologics are added for inadequate response. Systemic JIA is increasingly managed with early IL-1 or IL-6 blockade.

Prognosis

  • ~50% achieve remission without sequelae
  • ~25% have mild disability
  • ~20–25% develop crippling arthritis, blindness, or both
  • Oligoarticular persistent form carries the best prognosis; RF-positive polyarticular and systemic JIA have higher morbidity

Key Images

Systemic JIA — salmon-pink rash and ankle swelling, with resolution after canakinumab
Systemic JIA: ankle periarticular swelling (A), characteristic salmon-pink maculopapular rash (B), pre-treatment rash on trunk/limbs (C), and complete resolution 3 months after canakinumab (D).
Polyarticular JIA — bilateral symmetric deformities
Polyarticular JIA with symmetric multi-joint deformities including wrist/MCP/ankle involvement and contractures.
Oligoarticular JIA — asymmetric knee swelling
Bilateral knee effusions with synovial hypertrophy characteristic of JIA.
Sources: The Harriet Lane Handbook (23rd ed.); Miller's Review of Orthopaedics (9th ed.); Tintinalli's Emergency Medicine; Robbins & Kumar Basic Pathology
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