Paediatrics: Juvenile idiopathic arthritis: clinical principles and management

Juvenile idiopathic arthritis: clinical principles and management

Before labelling child with diagnosis of JIA it is imperative to exclude the differential diagnoses, the most important of which are sepsis, malignancy, and trauma.

History from carer and child

•   Limp, stiffness and loss of function, pain, or malaise.

•   Onset usually gradual. Beware of misleading history of trauma as young children frequently fall without significant injury.

•   History of non-use, or change in use.

•   Child may not complain of pain. Infant may be ‘irritable’.

•   Inflammatory symptoms: worse after rest or inactivity.

•   Stiffness is rarely volunteered. Parents sometimes describe child as ‘like a little old person in the mornings’. Toddler’s behaviour may be perceived as being difficult and uncooperative (e.g. refusing to move in the morning, then running in the afternoon).

•   History of associated rash, fever, weight loss.

•   History of sore throat, URTI, antecedent infections, and travel.

•   Family history of arthritis, psoriasis, colitis, rheumatic fever, or acute iritis.

Examination

•   Observe the child before they become self-conscious.

•   Watch them playing and walking.

•   Examine all the joints and spine for swelling, warmth, pain on movement, or limited movement.

•   Measure for leg length inequality and pelvic tilt.

•   Examine muscle bulk around affected joints.

•   Assess general muscle strength.

•   Examine the skin, hair and nails for rashes, psoriasis.

•   General examination: vital signs, height, weight, and BP.

•   Examine mouth and palate for ulcers, dentition; fauces for asymptomatic tonsillitis; heart for murmurs; abdomen for hepatosplenomegaly.

Investigations

•   FBC may show mild anaemia and thrombocytosis.

•   Neutrophilia suggests sepsis or systemic JIA.

•   Severe anaemia or thrombocytopenia: consider leukaemia.

•   ESR/CRP usually normal or mildly elevated. Very high levels suggest infection or malignancy. High ESR plus thrombocytopenia suggests leukaemia.

•   Infection screen: throat swab, urinalysis, blood for ASOT, viral serology (CMV, EBV, parvovirus B19, hepatitis) and culture.

•   Rheumatoid factor: non-specific test, but significant in polyarthritis (>5 joints). Exclusion criterion for oligoarticular JIA.

• ANA: non-specific (5% children ANA +ve). In oligoarticular JIA limited prognostic determinant for iritis.

• Muscle enzymes (CK, LDH, aldolase) raised in dermatomyositis, but can be normal. Very high LDH suggests malignancy.

• Imaging

•   radiographs—exclude fracture or tumour; early JIA—soft tissue swelling, and juxta-articular osteopenia; later—joint space narrowing and erosions;

•   US—helpful for confirming synovitis and joint effusion;

•   MRI—useful for atypical monoarthritis; gadolinium-enhanced MRI is gold standard for diagnosis of synovitis, but does not differentiate from sepsis.

• Synovial fluid aspirate: culture for sepsis. Microscopy rarely helpful.

Management

General

• Establish diagnosis and counsel child and parents.

• Start treatment as soon as possible.

• Most children will need regular hospital review to look for presence or reappearance of thickened synovium or effusions.

• Exercise: regular, daily aerobic and ‘range of motion’ exercises.

• Psychological support for children and carers: education and support groups (e.g. Arthritis Research Campaign).

• Ask about school performance and support at school.

• Adolescents may need counselling about contraception and alcohol if taking MTX.

• Amyloidosis: rare complication of severe disease.

Joints

• Minimize pain and stiffness using NSAIDs:

•   ibuprofen (30–40mg/kg);

•   diclofenac (1.5–2.5mg/kg bd);

•   naproxen (5–15mg/kg bd);

•   piroxicam (5–20mg daily according to weight).

• Prevent deformity: regular daily exercises; night splints; intra-articular steroid injections (triamcinolone) may settle inflammation for years.

• Control disease activity: MTX oral or SC in resistant cases.

• Etanercept: anti- tumour necrosis factor (TNF) if unresponsive to NSAIDs and SC MTX.

Eye screen for uveitis

Must have regular screening, initially 3-monthly, by experienced ophthal-mologist. Treat with topical steroids and midriatics. Course is independent of joint disease severity. Potentially blinding.

Growth 

Measure growth velocity; nutritional status; muscular atrophy.

Dentition 

Watch for caries.

Once the diagnosis is established the child should be looked after by a paediatric rheumatologist for specialist drugs and co-ordinating multi-disciplinary support.