Juvenile Idiopathic Arthritis (JIA) in Infants: Subtypes, Complications, and Management
Juvenile Idiopathic Arthritis (JIA) is the most common chronic rheumatic disease of childhood (<16 yr). Infant onset (<2 yr) is rare but distinct.
JIA Subtypes Relevant to Infants
| Subtype | Features | Infant Presentation |
|---|
| Systemic JIA (sJIA) | Quotidian fever, evanescent rash, hepatosplenomegaly, lymphadenopathy, serositis. Autoinflammatory (IL-1/IL-6 driven). | Most common in infancy. May lack arthritis initially. High macrophage activation syndrome (MAS) risk. |
| Oligoarticular JIA | ≤4 joints first 6 mo. High ANA+. ↑ Uveitis risk. | Knee/ankle swelling; often late walker. Uveitis screening critical. |
| Polyarticular JIA (RF−) | ≥5 joints. Symmetric small + large joints. | Diffuse swelling, irritability, failure to thrive. |
| Enthesitis-related (ERA) | Enthesitis + arthritis. HLA-B27+. Axial involvement later. | Rare <2 yr; presents as heel pain, refusal to bear weight. |
Infant-Specific Complications
- Growth disturbance: Chronic synovitis → epiphyseal overgrowth (leg length discrepancy) or growth arrest.
- Developmental delay: Pain → reduced mobility → motor/social delays.
- Uveitis: Asymptomatic; screen q3–4 mo (slit lamp) if ANA+ oligoarticular; q6–12 mo others.
- Macrophage Activation Syndrome (MAS): Life-threatening cytokine storm (sJIA). Ferritin >10,000, triglycerides ↑, fibrinogen ↓, cytopenias. ICU emergency.
Multidisciplinary Management
- Pediatric Rheumatologist – leads immunosuppression.
- Physical/Occupational Therapy – joint ROM, splinting, developmental support.
- Ophthalmology – uveitis screening/treatment.
- Orthopedics – leg length, contractures, joint injections.
- Psychosocial – family support, school liaison.
Medication Ladder (JIA)
- NSAIDs (naproxen) – symptom control only.
- Intra-articular glucocorticoids – bridge/oligoarticular.
- Conventional DMARD: Methotrexate (anchor drug; folate supplement).
- Biologics: TNFi (etanercept, adalimumab), IL-6R (tocilizumab) for sJIA/poly, IL-1 (anakinra, canakinumab) for sJIA/MAS.
- JAK inhibitors (tofacitinib) – newer option.
Early aggressive treatment → remission → normal development. Delayed diagnosis = irreversible joint damage.
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