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.
- Systemic (with fever and rash) (5-15%)
- Oligoarthritis (≤ 4 joints involved) (M/C 60-70%)
- 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
- Evanescent maculopapular rash
- 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
- RF+ (more severe)



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)