AKT · Musculoskeletal/Inflammatory arthritislow yield

Juvenile idiopathic arthritis

Chronic arthritis with onset 6 weeks, of unknown cause

Overview

Arthritis beginning before age 16 and lasting more than 6 weeks, with several subtypes (oligoarticular — the commonest, polyarticular, systemic/Still's disease, enthesitis-related, psoriatic). Systemic JIA (Still's) presents with quotidian fever, a salmon-pink rash and arthritis. The major sight-threatening complication is chronic anterior uveitis, which is often asymptomatic and needs screening. Detailed paediatric management is on the child_health page.

Recognise

Oligoarticular (≤4 joints, young girls, ANA-positive) — highest uveitis risk; polyarticular (RF-negative or RF-positive RA-like)
Systemic JIA (Still's): daily spiking fever, evanescent salmon-pink rash, arthritis, lymphadenopathy, serositis; risk of macrophage activation syndrome
Chronic anterior uveitis is frequently ASYMPTOMATIC → mandatory slit-lamp screening

Red flags

Macrophage activation syndrome in systemic JIA (cytopenias, very high ferritin, coagulopathy) → emergency
Untreated uveitis → cataract, glaucoma, blindness — screen even when the eye looks normal

Differentials & how to tell them apart

Septic arthritis / osteomyelitisacute, febrile, single joint — exclude

Leukaemiabone pain, cytopenias, blasts — a key mimic of systemic/joint symptoms in children

Reactive arthritis / HSPpost-infectious; HSP has purpura

Investigations

Clinical diagnosis of exclusion; ANA (uveitis risk), RF, HLA-B27 by subtype; inflammatory markers and ferritin (systemic JIA/MAS); slit-lamp screening for uveitis; exclude infection/malignancy (leukaemia can mimic).

Management

NSAIDs + intra-articular steroid → methotrexate → biologics; mandatory uveitis screening

1Diagnose by exclusion and subtype. Oligoarticular disease → NSAIDs and intra-articular corticosteroids; arrange mandatory slit-lamp uveitis screening regardless of eye symptoms.Gate: Systemic JIA with cytopenias + very high ferritin + coagulopathy → macrophage activation syndrome, a haematological emergency.
2Polyarticular/persistent → methotrexate; refractory or systemic disease → biologics (IL-1/IL-6 for systemic JIA). Full paediatric management on the child_health page.

NSAIDs + intra-articular corticosteroid — first-line for oligoarticular disease

Methotrexate — for polyarticular/persistent disease

Biologics (anti-TNF, IL-1/IL-6 inhibitors) — refractory or systemic JIA (IL-1/IL-6 for systemic disease)

Uveitis screening + treatment — regular slit-lamp; topical steroids/methotrexate for eye disease

Key points

Arthritis 6 weeks = JIA. Oligoarticular ANA-positive girls have the highest uveitis risk — screen the asymptomatic eye. Systemic JIA = daily fever + salmon-pink rash + arthritis; watch for macrophage activation syndrome. Exclude leukaemia.

Monitor & prognosis

Joint activity, growth, slit-lamp uveitis screening, MAS markers in systemic disease.

Many remit; uveitis and systemic complications drive morbidity if missed.

Source: Cross-ref child_health; BSPAR/NICE