Key learning

  • Most common chronic joint inflammation commencing in children under 16
  • Subtypes include 
    • Pauciarticular (most common)
    • Polyarticular
    • Systemic (Still’s)
    • Psoriatic
    • Enthesitis-related
  • Most commonly affects knees, ankles and wrists.
  • Clinical features
    • Joint swelling, tenderness, reduced ROM.
  • Management
    • Refer to paediatric rheumatology
    • NSAIDs first line in pauciarticular
    • DMARDs in polyarthritis
  • Complications
    • Uveitis (ANA positive)
    • Joint contracture
    • Growth disturbances
    • Osteoporosis
    • Anaemia

 

Definition

  • Joint swelling for more than 6 weeks
  • Less than 16 years old
  • No defined cause

Pathophysiology

  • Autoimmune disorder causing chronic inflammation of the joints 
  • It involves dysregulation of the immune system, leading to joint damage and other systemic manifestations.
  • Idiopathic cause- likely genetic predisposition and environmental triggers such as infection or autoimmune reaction

Epidemiology

  • Most common chronic childhood inflammatory arthritis

Subtypes

  • Pauciarticular JIA
    • Most common form (60%)
    • Persistent oligoarthritis
    • Good prognosis (< 4 joints affected)
  • RhF negative 
  • RhF positive
    • Poorer prognosis
    • Similarities with RA
  • Still's disease
    • Systemic arthritis
    • Clinical features:
      • General malaise
      • Fever
      • Salmon-pink rash
      • Hepatosplenomegaly
      • Lymphadenopathy
    • Investigations
      • RhF negative
      • ANA positive
  • Psoriatic
  • Enthesitis-related 
  • Undifferentiated

History

  • Joint pain and stiffness
  • Reduced range of motion
  • Worse in morning or after periods of inactivity
  • Most commonly knees, ankles and wrists
  • Can be associated fever, rash, lethargy

Examination Findings 

  • Swelling, tenderness, and limited range of motion of affected joints
  • Eye examination important to assess for uveitis 
  • Leg length or digit length discrepancy due to bone expansion
  • Deformities i.e. valgus deformity

Investigations

Help to rule out other causes (fractures, tumors, infection or congenital defects) 

  • CRP/ESR (may be elevated)
  • Hb (associated anaemia)
  • Platelets (associated thrombocytosis)
  • RhF (positive in 5%, poorer outcomes)
  • HLA B27 (associated with Enthesitis/spondylitis-related arthritis) 
  • XR/US/MRI of affected joints 

Diagnosis 

  • Exclusion of other causes of arthritis 
  • Classification criteria from the International League of Associations for Rheumatology (ILAR) may aid diagnosis

Management

  • Refer to paediatric rheumatologist
  • Symptom relief
  • 1st line pauciarticular = NSAIDs
  • 1st line polyarthritis (> 4 joints)= DMARDs (methotrexate)
  • 1st line persistent oligoarthritis = intra-articular steroid injections
  • Refractory cases
    • Systemic steroids
    • Biological agents
  • Physiotherapy and occupational therapy alongside above to help preserve function and activities of daily living

Complications

  • Uveitis (ANA positive patients)
  • Joint contracture
  • Growth disturbances
  • Osteoporosis
  • Amyloidosis
  • Anaemia
  • Psychosocial impact 

 

Useful links

BMJ Best Practice- Juvenile Idiopathic Arthritis