Paediatrics chapters
Juvenile idiopathic arthritis
The commonest chronic arthritis of childhood: how it is defined, the oligoarticular, polyarticular and systemic-onset types, the silent uveitis that needs eye screening, the tests that help and the drugs used from NSAIDs to methotrexate and biologics.
- JIA is arthritis in at least one joint for 6 weeks or more, starting before 16 years, after other causes are excluded; it is the commonest chronic rheumatic disease of childhood (about 1 in 1,000).
- Types by joints in the first 6 months: oligoarticular (4 or fewer joints, about half, young girls, ANA positive, highest uveitis risk), polyarticular (5 or more) and systemic onset (quotidian fever, salmon-pink rash, organomegaly, serositis).
- There is no diagnostic test: do a blood count to exclude leukaemia, ANA for uveitis risk, RF in older children; treat with NSAIDs, then methotrexate, biologics, joint injections and physiotherapy, with regular slit-lamp eye checks.
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Overview
Juvenile idiopathic arthritis (JIA) (the older name was juvenile rheumatoid arthritis, JRA) is a group of chronic arthritides of unknown cause that begin in childhood. Their shared feature is chronic synovitis. JIA is the most common chronic rheumatic disease of children.
It matters because untreated synovitis destroys joints and disturbs growth, and because the associated uveitis can cause blindness without any symptoms. Exams test the definition, the types, the uveitis risk, the investigations (and the need to exclude leukaemia), and the order of treatment.
Diagnostic criteria
JIA is a clinical diagnosis of exclusion. All of these are needed:
| Criterion | Detail |
|---|---|
| Age at onset | Under 16 years (the label stays even when the child becomes an adult) |
| Arthritis | In one or more joints: swelling or effusion, or at least two of: limited movement, pain or tenderness on movement, increased heat |
| Duration | At least 6 weeks |
| Exclusion | Other causes of arthritis actively excluded |
Joint pain alone (arthralgia) is not arthritis. And arthritis lasting only a few days or weeks suggests a reactive, viral or septic cause rather than JIA.
Classification
The type is decided by the pattern in the first 6 months of illness.
| Feature | Oligoarticular | Polyarticular | Systemic onset | Spondyloarthropathy (enthesitis-related) |
|---|---|---|---|---|
| Joints | Fewer than 5 (4 or fewer) | 5 or more | Varies, usually 5 or more | Varies |
| Joint type | Medium to large: knee, ankle, wrist | Small and medium, symmetric | Small and medium | Large lower limb joints, sacroiliac, spine |
| Share of cases | About 50% | About 40% | About 10% | Smaller group |
| Sex | Girls, especially young | Girls | Equal | Boys |
| Systemic features | None | Some (low fever, malaise) | Prominent | Some |
| Eye disease | +++ chronic uveitis | ++ uveitis | + (rare) | Acute iritis |
| ANA | Often positive | Sometimes | Negative | Negative |
| RF | Negative | Positive in an adolescent subgroup | Negative | Negative |
| Outcome | Excellent (over 90% remission) | Good, some disability | Variable, worst joints | Variable |
Other groups in the modern classification include psoriatic arthritis and enthesitis-related arthritis.
Oligoarticular JIA
- The commonest form; peaks at 1-3 years (and a second peak around 8-12 years).
- Knee most often, then ankle and wrist; small joints, neck and hip are unusual.
- The child is well: no fever, no weight loss, normal blood count and ESR.
- Positive ANA in many; these children, especially young girls, have the highest risk of chronic uveitis.
- Asymmetric knee disease can cause leg length discrepancy (the growth plate near an inflamed joint overgrows).
- Some later involve more joints (extended oligoarthritis).
Polyarticular JIA
- Five or more joints, usually symmetric, including small joints of hands and feet, wrists, knees, ankles.
- Cervical spine may be involved; fusion of upper cervical vertebrae and atlantoaxial subluxation can occur.
- Mild systemic features: low-grade fever, malaise, growth retardation, anaemia of chronic disease, raised inflammatory markers.
- RF-positive disease in adolescent girls behaves like adult rheumatoid arthritis (anti-CCP positive, erosive, poorer outlook); HLA-DR4 is common in this group.
Systemic-onset JIA (Still disease)
Thought to be autoinflammatory. Fever and systemic illness come before the arthritis.
- Fever: daily (quotidian) spikes, once or twice a day, lasting at least 2 weeks and documented daily for at least 3 days, with a normal or low temperature in between.
- With one or more of:
- Evanescent salmon-pink rash (macular, morbilliform), seen mainly with fever spikes.
- Generalised lymph node enlargement.
- Hepatomegaly and/or splenomegaly (about 70%).
- Serositis: pleuritis or pericarditis (about 50%); tamponade is rare.
- The child looks ill, with malaise and failure to thrive.
- Arthritis follows the systemic phase by 6 weeks to 6 months; a definite diagnosis is not possible until arthritis appears.
- Labs: very high ESR and CRP, neutrophil leucocytosis, thrombocytosis, anaemia; ANA and RF negative.
- Equal sex ratio; the arthritis can be extensive and resistant, giving the highest risk of long-term disability.
- A falling white cell count during active systemic disease should raise concern for macrophage activation.
"Salmon, Spikes, Spleen, Serositis" = systemic-onset JIA.
Spondyloarthropathies
Juvenile ankylosing spondylitis, psoriatic arthritis and arthritis of inflammatory bowel disease. Features: older boys, HLA-B27, enthesitis (inflammation where tendons insert into bone), sacroiliac and back involvement, symptomatic acute iritis, and psoriasis or bowel symptoms that may appear later.
Aetiology and triggers
- Cause unknown; thought to need immunogenetic susceptibility plus an environmental trigger.
- Viruses suggested as triggers: parvovirus B19, rubella and Epstein-Barr virus (Akbar).
- HLA links (Akbar and Nelson): HLA-DR4 with RF-positive polyarticular disease; HLA-A2, DR5 and DR8 with oligoarticular disease; HLA-DR5, DR6 and DR8 with uveitis; HLA-B27 with spondyloarthropathy.
Pathophysiology
- The synovium becomes thick and hypervascular, with villous hypertrophy, oedema and infiltration by lymphocytes and plasma cells.
- Inflammatory cytokines cause release of proteases and collagenases.
- In advanced disease pannus forms and erodes articular cartilage and bone.
- Inflammation near an active growth plate speeds growth (bony overgrowth, leg length discrepancy) or later causes early fusion; inflamed growth centres may be malformed (crowded carpal bones, micrognathia from temporomandibular joint disease).
Clinical presentation (general)
- Onset is slow, but swelling is often noticed suddenly, for example after a fall, and is mistaken for injury.
- Morning stiffness and gelling; the child is slow to get up and may limp.
- Pain is often mild; the child rarely refuses to use the joint completely (unlike septic arthritis).
- Joint is swollen, warm, tender, with effusion and limited movement; later contractures.
Uveitis (chronic iridocyclitis)
- Any child with chronic arthritis can develop it; the risk is highest in young girls with oligoarticular JIA and positive ANA.
- It is chronic anterior uveitis that is painless and asymptomatic until vision is damaged; Akbar notes it is bilateral in about two-thirds.
- It is a treatable cause of childhood blindness, so regular slit-lamp examination (looking for anterior chamber inflammation) is essential, even when the joints are quiet.
- By contrast, the iritis of spondyloarthropathy is acute and painful (red eye).
Positive ANA in JIA predicts uveitis, not more severe arthritis. Screen the eyes with a slit lamp.
Investigations
There is no diagnostic test; tests support the diagnosis, exclude mimics and stratify risk.
| Test | Purpose and typical result |
|---|---|
| Full blood count | Essential in any child with joint or bone pain to exclude leukaemia; anaemia of chronic disease; high white cells and platelets in systemic disease; normal in oligoarticular |
| ESR, CRP | Normal in oligoarticular; raised in polyarticular and very high in systemic onset |
| ANA | For all oligoarticular cases: identifies uveitis risk |
| Rheumatoid factor, anti-CCP | In older children with polyarticular disease: identifies adult-type RA |
| HLA-B27 | If spondyloarthropathy suspected |
| Joint aspiration | In an acute single hot joint, to exclude septic arthritis: JIA fluid usually has fewer than 50,000-100,000 cells, mainly lymphocytes, Gram stain and culture negative |
| X-ray | Usually normal early; later periarticular osteopenia, growth centre changes, and erosions late |
| MRI, ultrasound | Detect synovitis and effusion earlier than X-ray |
| Synovial biopsy | For a persistent single joint not responding to treatment, to exclude tuberculosis or other chronic infection |
Differential diagnosis
| Group | Examples |
|---|---|
| Infection | Septic arthritis, osteomyelitis, tuberculous arthritis, viral arthritis, Lyme disease |
| Reactive and post-infectious | Rheumatic fever, post-streptococcal arthritis, Henoch-Schonlein purpura, transient synovitis of the hip, reactive arthritis |
| Other connective tissue disease | SLE, juvenile dermatomyositis, scleroderma, vasculitis, Kawasaki disease |
| Malignancy | Leukaemia, lymphoma, neuroblastoma, bone and joint tumours |
| Orthopaedic and trauma | Traumatic arthritis, Perthes disease, slipped capital femoral epiphysis |
| Others | Haemophilia, sickle cell disease, growing pains, hypermobility, rickets |
- Rheumatic fever: exquisitely painful, migratory polyarthritis of large joints with remittent fever, lasting days per joint; JIA is persistent and less painful.
- Leukaemia: bone pain out of proportion, night pain, cytopenias or blasts.
- SLE: adolescent girls, malar rash, cytopenias, low complement, anti-dsDNA.
Systemic-onset JIA must be distinguished from infection and malignancy (leukaemia, neuroblastoma) before it is labelled JIA; it is a diagnosis of exclusion.
Management
Goals: control inflammation, relieve pain, keep joints moving, prevent deformity, restore function and prevent blindness. Care is by a team: paediatrician or rheumatologist, physiotherapist, ophthalmologist.
General measures
- Physiotherapy and occupational therapy: range-of-motion and muscle-strengthening exercises; taught to the family as a home programme.
- Bed rest is unnecessary apart from the most acute phase.
- Splints to prevent deformity; surgery (including joint replacement) for established damage.
Drugs
| Step | Drug | Notes |
|---|---|---|
| First line | NSAIDs | Control pain, swelling and fever. Akbar: naproxen 15 mg/kg/day in two doses (maximum 500 mg per dose) or ibuprofen 40 mg/kg/day in three doses (maximum 800 mg per dose); others include indomethacin and meloxicam |
| Few joints | Intra-articular corticosteroid | Useful in oligoarticular disease |
| Second line | Methotrexate (oral or subcutaneous, once weekly) | Drug of choice for polyarticular and systemic disease not controlled by NSAIDs; Akbar: 0.5-1 mg/kg once a week (maximum 25 mg/week); response in about 3-4 weeks; monitor for marrow suppression and liver toxicity |
| Other DMARDs | Hydroxychloroquine, sulfasalazine, leflunomide | For incomplete response |
| Biologics | Anti-TNF: etanercept, infliximab, adalimumab | Resistant disease and spondyloarthropathy; risk of serious infection and possibly malignancy |
| Systemic JIA | Anakinra (IL-1 receptor antagonist) | Very effective for systemic features |
| Severe disease only | Systemic corticosteroids | Severe systemic JIA with organ involvement (e.g. pericarditis) or arthritis preventing walking; used as a bridge until other drugs act; avoid otherwise |
NSAIDs first, methotrexate second, biologics third. Systemic steroids are kept for severe systemic disease and as a short bridge.
Long-term monitoring
- Slit-lamp eye examinations at regular intervals of a few months, most often in ANA-positive oligoarticular disease.
- Methotrexate: blood counts and liver tests.
- Growth, weight and leg length; jaw growth.
- Joint range, function and contractures; cervical spine in polyarticular disease.
- Disease activity and inflammatory markers; drug side effects (infection on biologics, steroid effects).
Complications
- Joint contractures, bony fusion, loss of joint space, erosions.
- Growth problems: limb length discrepancy, local overgrowth or undergrowth, generalised short stature (the younger the onset, the greater the risk), micrognathia.
- Uveitis leading to visual loss or blindness if missed.
- Atlantoaxial subluxation.
- In systemic disease: pericardial tamponade, macrophage activation.
Prognosis and counselling
- Overall good: Nelson quotes about 85% complete remission.
- Oligoarticular: excellent; most do well.
- Most disabled children have polyarticular or systemic-onset disease.
- Poor prognostic features: systemic onset, positive rheumatoid factor, poor response to treatment, erosions on X-ray.
- The disease may flare and remit. Families should be told that physical limitations can persist into adult life even after the disease settles, so physiotherapy is lifelong in importance, and that eye checks must continue even when the joints are quiet.
Expect: the definition (onset under 16, 6 weeks, exclusion); types by joint count in the first 6 months; oligoarticular JIA as the commonest type with knee involvement, young girls and positive ANA; chronic painless uveitis and slit-lamp screening; systemic-onset JIA with quotidian fever, salmon-pink rash, hepatosplenomegaly, serositis, high platelets and negative ANA and RF; blood count to exclude leukaemia; RF-positive adolescent polyarthritis behaving like adult RA; NSAIDs then methotrexate then anti-TNF agents; poor prognostic factors.
Quick revision
- Arthritis 6 weeks or more, onset under 16 years, other causes excluded.
- Commonest chronic rheumatic disease of children; about 1 in 1,000.
- Oligoarticular: 4 or fewer joints, knee, young girls, ANA positive, uveitis risk, excellent outcome.
- Polyarticular: 5 or more joints, symmetric, small joints; RF-positive teenage girls resemble adult RA.
- Systemic onset: quotidian fever, salmon rash, organomegaly, serositis; ANA and RF negative.
- No diagnostic test; always check the blood count to exclude leukaemia.
- NSAIDs first; methotrexate weekly next; anti-TNF and anakinra for resistant disease.
- Steroids only for severe systemic disease or as a bridge; joint injections for few joints.
- Lifelong physiotherapy and regular slit-lamp checks.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).
FAQ
Why does a child with JIA and no eye symptoms need eye checks?
The uveitis of JIA is usually painless and silent until vision is damaged. Regular slit-lamp examination finds it early, especially in young girls with oligoarticular disease and positive ANA.
Is a positive rheumatoid factor needed to diagnose JIA?
No. Most children with JIA are RF negative. A positive RF is mainly seen in adolescent girls with polyarticular disease and predicts a course like adult rheumatoid arthritis.
Can systemic-onset JIA be diagnosed before arthritis appears?
Only presumptively. A definite diagnosis needs arthritis, which may follow the fever and rash by weeks to months, and infection and malignancy must be excluded first.
Which drug is used when NSAIDs are not enough?
Methotrexate given once weekly by mouth or injection is the usual next step, with blood counts and liver tests monitored. Biologic drugs such as anti-TNF agents are added for resistant disease.