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Musculoskeletal System ORGAN SYSTEMS

Juvenile Idiopathic Arthritis (JIA)

Arthritis of ≥ 1 joints at < 16 years and persisting for ≥ 6 weeks.

Arthritis of ≥ 1 joints at < 16 years and persisting for ≥ 6 weeks.

Classification

  • Systemic arthritis
  • Oligoarthritis:
    • Persistent
    • Extended
  • Polyarthritis:
    • Rheumatoid factor negative
    • Rheumatoid factor positive
  • Psoriatic arthritis
  • Enthesitis-related arthritis
  • Undifferentiated arthritis:
    • Fits no other category
    • Fits more than one category

Etiology

Environmental triggers:

  • Rubella
  • Parvovirus B19
  • Mycobacterium tuberculosis
  • Mycoplasma pneumoniae
  • Enteric organisms
  • Physical trauma
  • Psychological stress

Host factors:

  • Major histocompatibility complex (MHC) associated genetic predisposition

Autoimmune mechanism:

  • Complement activation & Consumption
  • CICs (Circulating immune complexes): In blood, synovium, synovial fluid
  • Increased expression of activation markers in T-lymphocytes
  • Autoantibodies: Antinuclear, anti-smooth muscle
  • IgM rheumatoid factor (RF) negative

Presentation

Clinical subtypes:

3 major types of onset are described according to the presentation during the first 6 months of disease, viz.
  1. Systemic (with fever and rash) (5-15%)
  2. Oligoarthritis (≤ 4 joints involved) (M/C 60-70%)
  3. Polyarthritis (> 4 joints involved) (25-30%)

Systemic-onset JIA (sJIA) “Still’s disease”

Acute onset disease with prominent systemic features
  • Quotidian fever: Characteristic twice daily peak
    • Prominent in the evening hours
    • Accompanied by characteristic rash:
      • Evanescent maculopapular rash
        • With central clearing
        • Prominent on the trunk
  • Marked irritability (decreases with subsidence of fever)
  • Serosal involvement:
    • Pericarditis or pleuritis
  • Hepatosplenomegaly
  • Lymphadenopathy

II. Pauciarticular/Oligoarticular Onset JRA

≤ 4 joints (usually large) are affected during the first 6 months of the disease
  • Asymmetrical joint involvement (large joints)
    • Joint swelling > joint pain
  • Subtypes:
    • Persistent (if number of affected joints continues to be ≤4)
    • Extended (if number of affected joints > 4 during the disease course)

Polyarticular-onset JRA:

Joint pain, out of proportion to the degree of joint swelling, is the usual complaint
  • Fever
  • Malaise
  • Subtypes:
    • RF+ (more severe)
      • Onset: Late childhood/early adolescence
      • Affected joints: Symmetrical, additive, severe and deforming and typically involves the small joints of the hand,
    • RF- (less severe)
      • Onset: Any age
      • Affected joints: Knees, wrists and hips
Right ankle demonstrating atrophy and hypopigmentation secondary to corticosteroid injection
Right ankle demonstrating atrophy and hypopigmentation secondary to corticosteroid injection. | PJ, H. and RM, L. (2005) ‘Medical treatment of juvenile idiopathic arthritis’, JAMA, 294(13), pp. 1671–1684. Available at: http://dx.doi.org/10.1001/jama.294.13.1671.
Severe growth deformities involving fingers
A, Severe growth deformities involving fingers. B, Same patient demonstrating severe growth deformities involving toes. | PJ, H. and RM, L. (2005) ‘Medical treatment of juvenile idiopathic arthritis’, JAMA, 294(13), pp. 1671–1684. Available at: http://dx.doi.org/10.1001/jama.294.13.1671.
Three-year-old girl with oligoarthritis involving the left knee.
A, Three-year-old girl with oligoarthritis involving the left knee. Swelling, flexion contracture, muscle wasting, and a longer leg on the affected side. B, Patient with systemic arthritis demonstrating characteristic erythematous macular rash on forearm with Koebner phenomena (exacerbation of rash by minor trauma). | PJ, H. and RM, L. (2005) ‘Medical treatment of juvenile idiopathic arthritis’, JAMA, 294(13), pp. 1671–1684. Available at: http://dx.doi.org/10.1001/jama.294.13.1671.

Complications

  • Anemia
  • Chronic anterior uveitis

Systemic-onset disease:

  • Macrophage activation syndrome: Potentially life-threatening complication manifesting as sudden onset icterus, bleeding tendency, leukopenia, thrombocytopenia, elevated triglycerides and raised ferritin levels.
    • ℞ IV methylprednisolone pulses

Longstanding disease:

  • Growth disturbances
  • Limb length discrepancies
  • Joint contractures 

Diagnosis

  • Arthritis pattern recognition: M/imp diagnostic clue
  • Synovial fluid aspiration: Microscopy and culture
  • Complete blood counts
  • C-reactive protein: Surrogate marker of disease activity
  • Bone marrow aspiration: Necessary if use of glucocorticoids is being contemplated for treatment of JIA

Management

Multidisciplinary management

  • Physiotherapy
  • Occupational therapy

Medical management

  • NSAIDs (mainstay treatment) (4-6 weeks)
    • Naproxen
    • Ibuprofen
  • Selective COX-2 inhibitors
  • Associated with polyarthritis:
    • Weekly methotrexate (15-25 mg/m2/week SC/orally) ± Hydroxychloroquine
  • Oligoarthritis non-responsive to initial NSAID treatment:
    • Intra-articular injections of glucocorticoids (usually, triamcinolone)
  • Newer modalities of treatment: Biologicals
    • Anakinra (IL-1 receptor antagonist)
    • Canakinumab (monoclonal antibody to IL-1)
    • Tocilizumab (monoclonal antibody to IL6 receptor)
    • Infliximab, golimumab and adalimumab (monoclonal antibodies to TNFa)
    • Etanercept (recombinant soluble TNF receptor p75 fusion protein)
    • Abatacept (inhibitor of T-cell activation)

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