Juvenile idiopathic arthritis (JIA)

M08.0

DESCRIPTION

Juvenile Idiopathic Arthritis (JIA) is defined as arthritis of unknown origin for at least 6 weeks with onset before the age of 16 years. Other causes of arthritis must be excluded e.g. infections, malignancy, trauma, other autoimmune disease. Different clinical subgroups are recognised according to the pattern of onset that manifests within the first 6 months.

DIAGNOSTIC CRITERIA

Systemic onset

  • Arthritis in one or more joints.
  • Plus 2 weeks of daily (quotidian) fever.
  • With one of the following:
    • erythematous macular rash, or
    • serositis, i.e. pericarditis and pleuritis, or
    • hepatosplenomegaly, or
    • generalised lymphadenopathy.

Oligoarthritis

Always consider TB if only one joint is involved.

  • Arthritis affecting one to four joints for first 6 months of disease.
  • Two categories are recognised:
    • Persistent oligoarthritis: affects ≤ 4 joints throughout disease course.
    • Extended oligoarthritis: affects > 4 joints after the first 6 months.
  • Occurs more commonly in girls than in boys.
  • Has early onset before 6 years of age.
  • Usually asymmetric arthritis that affects mainly large joints.
  • High risk of developing chronic iridocyclitis.
  • 65–85% of patients are anti-nuclear antibody (ANA) positive.

Polyarthritis (Rheumatoid factor negative)

  • Arthritis affecting ≥ 5 joints in first 6 months of disease.
  • Negative rheumatoid factor polyarthritis includes 2 subsets:
    • one that is similar to adult onset RF negative rheumatoid arthritis characterised by a symmetric synovitis of large and small joints, onset at school age and absence of ANA expression;
    • another that resembles oligoarthritis apart from the number of joints affected in the first 6 months of the disease.

Polyarthritis (Rheumatoid factor positive)

  • Arthritis affecting ≥ 5 joints in first 6 months.
  • Positive rheumatoid factor on 2 separate occasions at least three months apart.
  • Involves large and small joints.

Enthesitis related arthritis

  • Arthritis and enthesitis or ,
  • arthritis or enthesitis and 2 of the following:
    • sacroiliac joint involvement,
    • HLA-B27 positive,
    • one 1ˢᵗ or 2ⁿᵈ degree relative with HLA-B27 associated disease,
    • arthritis in a boy after the age of 8 years,
    • anterior uveitis associated with pain, redness or photophobia.

Psoriatic Arthritis

  • Arthritis plus psoriasis in a child, or
  • Arthritis and 2 of the following:
    • dactylitis,
    • nail pitting,
    • psoriasis in a first degree relative.

Undifferentiated arthritis

  • Arthritis not meeting criteria for one of the above categories or fitting more than one of the above groups.

Differential diagnosis

JIA is a clinical diagnosis and depends on the persistence of arthritis or typical systemic manifestations and by exclusion of other diseases:

  • Pyogenic and tuberculous joint infection and osteomyelitis.
  • Arthritis associated with other acute infectious illnesses.
  • Acute leukaemia and other malignancies.
  • Acute rheumatic fever.
  • Auto immune disorders, SLE or mixed connective tissue disease.
  • Reiter syndrome, i.e. arthritis, urethritis and conjunctivitis.
  • Arthritis associated with inflammatory bowel disease.

Investigations

Investigations must be tailored for each case, in consultation with a specialist, consider the following investigations:

  • Full blood count with differential and platelet count.
  • C-reactive protein and erythrocyte sedimentation rate.
  • ALT for liver function screen before starting methotrexate.
  • Serum urea, creatinine and electrolytes.
  • Muscle enzymes, albumin, calcium, phosphate and alkaline phosphatase.
  • Auto-antibodies and rheumatoid factor.
  • X–ray or ultrasound of affected joints.
  • Arthroscopy and synovial biopsies in cases of possible TB arthritis.
  • Eye screen for uveitis.

GENERAL AND SUPPORTIVE MEASURES

  • Occupational and physiotherapy programs may provide the following:
    • exercises to increase range of movements of joints and to maintain muscle strength;
    • hot water baths, swimming pool exercises;
    • splints, e.g. nocturnal splints, for pain relief and prevention of contractures;
    • shoe inserts/raises;
    • aids for activities of daily living.
  • Orthodontic treatment if temporomandibular joints are involved.
  • All children should have slit lamp examination initially, with follow up thereafter at the discretion of the ophthalmologist.

MEDICINE TREATMENT

There is no cure for JIA.
Goal of treatment is to eliminate active disease, to normalise joint function, to preserve normal growth, to prevent long-term joint damage and disease complications. Outcome is improved with early aggressive therapy. Treatment should be decided in consultation with a specialist.

Oligoarthritis

NSAID, e.g.:

  • Ibuprofen, oral, 10 mg/kg/dose 6-8 hourly.

LoEIII [1]

NSAIDs as monotherapy are given for 1-2 months in patients with low disease activity and without joint contractures.

If no improvement:
ADD Intra-articular steroids.

  • Intra-articular corticosteroid injection for all active joints (rheumatologist or orthopaedic specialist):
  • Methylprednisolone acetate, 1 mg/kg with lignocaine 1%, 0.5 mL.
    • If no response: repeat in 3 months.
    • Young children may require light sedation with midazolam and ketamine.
    • Large joints, if possible, should be aspirated at same time.
    • Can be repeated after 3 months if there was an initial response, but the disease is not yet in remission.
    • Intra-articular steroids can also be used as initial therapy.

If disease activity still present after 3 months:
ADD

  • Methotrexate, oral, 10-15 mg/m²/week as a single dose on an empty stomach. Specialist initiated.
    • Increase dose at monthly intervals up to 1 mg/kg/week until there is satisfactory response, continue maintenance at the same dose.
    • Maximum dose: 25 mg/week.
    • Adverse effects include: nausea, mood changes, raised liver enzymes, bone marrow toxicity and protein/haematuria.
    • Monitor: Pre-treatment FBC, liver transaminases and creatinine; then FBC and either ALT or AST 3 monthly. Serum Creatinine 6 monthly.

PLUS

  • Folic acid, oral, 5 mg weekly, (on the day after methotrexate) for the duration of the treatment.

If no remission in 6 months, refer to a rheumatologist.

Note: Screen all patients early for uveitis (highest risk if ANA positive).

Polyarthritis – early

Start NSAID as soon as possible.

  • NSAID, e.g.:
  • Ibuprofen, oral, 10 mg/kg/dose 6-8 hourly.

LoEIII [1]

If no significant improvement in 1 month, or if severe, at onset, start disease modifying drugs (DMARDs):

  • Methotrexate, oral, 10–15 mg/m²/week as a single dose on an empty stomach. (Specialist initiated)
    • Maximum dose: 25 mg/week.

PLUS

  • Folic acid, oral, 5 mg weekly (on the day after methotrexate) for the duration of the treatment.

Note:
Intra-articular steroids (IAS) may be used in conjunction with methotrexate.

For rapid relief of symptoms in severe early disease consider adding:

  • Prednisone, oral, starting dose: 1 mg/kg/dose once daily.
    • Reduce dose gradually to 5 – 7.5 mg daily, depending on response.

Systemic onset JIA

Systemic JIA is an aggressive systemic disease. Refer to a rheumatologist early.
Initiate treatment after consultation with a rheumatologist.

  • NSAID, e.g.:
  • Ibuprofen, oral, 10 mg/kg/dose 6-8 hourly.

LoEIII [1]

For patients with mild disease begin with:

  • Prednisone oral, 2 mg/kg as a single daily dose.
    • Once disease is controlled, reduce dose gradually.

Critically ill patients with internal organ involvement, such as pleuritis, pericarditis, myocarditis or evidence of early macrophage activation syndrome should be referred urgently:

  • Methylprednisolone, IV, 30 mg/kg/day for 3 days.

Follow with:

  • Prednisone oral, 2 mg/kg as a single daily dose until disease is controlled.
    • These patients may respond to methotrexate or cyclosporine in the long term, but the response is not as good as other JIA patients.

Psoriatic arthritis

Treat as for oligoarthritis if ≤ 4 joints, or polyarthritis if severe disease or >4 joints at onset.
Refer early as most children will require a DMARD.

Enthesitis related arthritis

Start NSAID as soon as possible.

  • NSAID, e.g.:
    Ibuprofen, oral, 10 mg/kg/dose 6-8 hourly.

LoEIII [1]

If severe disease:

  • Prednisone, oral, 1–2 mg/kg as a single daily dose for 2 weeks and wean over 2 weeks.
    • If no remission in 2–4 months, refer.

Uveitis management

Manage in consultation with an ophthalmologist.

REFERRAL

  • Urgent: uncontrolled systemic disease.
  • Paediatrician referral:
    • All for confirmation of diagnosis.
    • All patients requiring DMARD.
    • Adverse reaction to NSAID.
    • Suspected JIA not responding to NSAID therapy.
  • Ophthalmology referral:
    • For slit lamp examination.
    • Patients with iridocyclitis and uveitis.
  • For orthopaedic treatment, e.g. where intra-articular corticosteroids is indicated, or if TB oligoarthritis is suspected.