Introduction
A child with a swollen, painful or stiff joint has a wide list of causes, from harmless to urgent. Juvenile idiopathic arthritis (JIA) is the commonest chronic rheumatic disease of childhood; reactive arthritis follows an infection; spondyloarthritis affects entheses and the spine and is linked to HLA-B27.
Juvenile idiopathic arthritis
Arthritis starting before 16 years, lasting at least 6 weeks, with other causes excluded. About 1 in 1000 children. Morning stiffness, swelling, limping, reduced range, less playing; pain is often mild.
Macrophage activation syndrome complicates systemic JIA: persistent fever, falling ESR and platelets, very high ferritin, high triglycerides, low fibrinogen, liver dysfunction, bleeding. It is life-threatening: high-dose steroids, ciclosporin, anakinra.
Tests
JIA is a clinical diagnosis; tests exclude others and classify: blood count and film (exclude leukaemia), CRP/ESR, ANA, rheumatoid factor, anti-CCP, HLA-B27; ultrasound or MRI of joints; joint aspiration if infection is possible. Eye screening by slit lamp every 3–6 months in oligo- and polyarticular JIA (uveitis has no symptoms and can blind).
Treatment
- NSAIDs (naproxen, ibuprofen) for symptoms.
- Intra-articular steroid (triamcinolone hexacetonide): first choice for oligoarthritis.
- Methotrexate weekly (with folic acid) for polyarthritis and resistant disease.
- Biologics: anti-TNF (etanercept, adalimumab, the latter also for uveitis), abatacept, tocilizumab; IL-1 or IL-6 blockade (anakinra, canakinumab, tocilizumab) for systemic JIA; JAK inhibitors.
- Physiotherapy, splints, exercise, school support, psychological help.