Juvenile Idiopathic Arthritis
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Direct answer
Arthritis for more than six weeks in a child under sixteen is juvenile idiopathic arthritis, classified into seven ILAR categories whose management differs sharply: oligoarticular disease (the commonest — young girls, antinuclear-antibody positive, silent uveitis risk) is treated with intra-articular triamcinolone hexacetonide and methotrexate; systemic JIA (quotidian fever, salmon-pink evanescent rash, serositis) responds to IL-1 and IL-6 blockade (anakinra, canakinumab, tocilizumab) rather than TNF inhibitors; enthesitis-related arthritis (older boys, HLA-B27) behaves like spondyloarthritis. The two sight- and life-threatening pieces of the topic are asymptomatic anterior uveitis, caught only by scheduled slit-lamp screening, and macrophage activation syndrome.
What you must remember
- Seven ILAR categories: systemic, oligoarticular (persistent and extended), polyarticular RF-negative, polyarticular RF-positive, psoriatic, enthesitis-related and undifferentiated.
- Systemic JIA: quotidian fever spiking to 39°C or more, with an evanescent salmon-pink rash that appears with the spike; arthritis may lag weeks behind; ferritin and ESR high, ANA and RF negative.
- MAS (2016 criteria): ferritin above 684 ng/mL plus any two of platelets 181 × 10⁹/L or below, AST above 48 U/L, triglycerides above 156 mg/dL, fibrinogen 360 mg/dL or below — a soaring ferritin with falling platelets is the bedside alarm; treat with anakinra and glucocorticoids in hospital.
- Uveitis risk pyramid: ANA-positive oligoarticular girls, onset under seven, disease duration under four years are highest risk — slit-lamp examination every three to four months; the eye is white and the child asymptomatic.
- Uveitis ladder: topical steroids with mydriatics, methotrexate, then adalimumab — etanercept is ineffective for uveitis, a recurrent exam point.
- Joint injection: triamcinolone hexacetonide is the preferred intra-articular steroid and often produces prolonged remission of an oligoarticular knee.
- Methotrexate 15 mg/m² weekly (oral or subcutaneous) with folic acid is the standard conventional DMARD; biologics follow category — IL-1 or IL-6 for systemic disease, anti-TNF or abatacept for polyarticular.
- Indian practice points: tuberculosis screening under NTEP before every biologic; older Indian textbooks and exams still use "juvenile rheumatoid arthritis" and "juvenile chronic arthritis", which mapped categories differently — expect viva questions on nomenclature.
Worked example: fever, rash and arthritis in a five-year-old
A five-year-old girl has daily fevers to 39.5°C for three weeks, spiking each evening, with a pink rash that appears with the spike and vanishes by morning; knees and wrists are now swollen, yet she is remarkably well between spikes. Build the differential first: leukaemia and other malignancies (night bone pain, cytopenias, blasts on the smear), infection including tuberculosis, Kawasaki disease (under five, five days of fever, conjunctival and mucosal changes, coronary aneurysms — treated with IV immunoglobulin 2 g/kg) and reactive arthritis.
The laboratory pattern settles it: neutrophil leucocytosis, high ESR and CRP, markedly raised ferritin, ANA and RF negative — systemic JIA. Management opens with an NSAID (naproxen or indometacin); if fever and arthritis persist beyond days to weeks, IL-1 blockade with anakinra is first-line and steroid-sparing, with canakinumab or tocilizumab as maintenance biologics. Throughout, watch for macrophage activation syndrome: a ferritin spike with falling platelets, rising triglycerides, transaminitis and a dropping fibrinogen — admit, treat with anakinra and glucocorticoids, and involve intensive care early. Growth, nutrition, physiotherapy and school reintegration are the long game, which is exactly why chronic steroids are avoided: they stunt the very child they are meant to protect.
Where students slip
Etanercept chosen for uveitis is the perennial wrong answer. Forgetting the slit lamp is the second — the eye is white, the child complains of nothing, and only the screening schedule protects sight. Escalating blanket immunosuppression for MAS without recognising it as hyperinflammation needing anakinra is the third. And the child with a single hot joint still needs an aspiration: septic arthritis happens in JIA patients too, and a flare and an infection look identical from the bedside.
Frequently asked questions
What age and duration define juvenile idiopathic arthritis?
Onset before the sixteenth birthday with objective arthritis lasting more than six weeks.
Which children need slit-lamp screening every three to four months?
ANA-positive girls with oligoarticular JIA, onset under seven and disease duration under four years — the highest-risk group for chronic anterior uveitis.
What are the 2016 criteria for macrophage activation syndrome?
Ferritin above 684 ng/mL plus any two of platelets 181 × 10⁹/L or below, AST above 48 U/L, triglycerides above 156 mg/dL and fibrinogen 360 mg/dL or below.
Which biologic is first-line in systemic JIA?
IL-1 blockade with anakinra, with canakinumab or tocilizumab for maintenance; TNF inhibitors underperform in this category.
Why does etanercept fail in JIA uveitis?
It does not control intraocular inflammation — adalimumab after methotrexate is the standard escalation pathway.
Which steroid is preferred for intra-articular injection in JIA?
Triamcinolone hexacetonide, long-acting, often producing prolonged remission of the injected joint.