Description

• Juvenile idiopathic arthritis (JIA) is the most common chronic pediatric rheumatologic disease.
• JIA is diagnosed before 16 years of age.
• JIA can be associated with significant disability and commonly involves ≥6 weeks of joint swelling, restricted range of motion, warmth, redness, and/or pain.
• Seven (International League of Associations for Rheumatology [ILAR]) subtypes determined by clinical characteristics in first 6 months of illness:
  • Systemic (sJIA): 10%; preceded by febrile onset of ≥2 weeks with rash, serositis, hepatosplenomegaly, or lymphadenopathy; arthritis may not be present initially; pathogenic role for IL-6 and IL-1
  • Polyarticular (PA): ≥5 joint involvement; large and small joints
    • PA with positive rheumatoid factor (RF): 2–7%; RF positive on two tests ≥3 months apart (1)[C]; uncommon in <9 years old
    • PA with negative RF: 15–20%; 50% of patients antinuclear antibodies (ANA) positive
  • Oligoarticular (OA): 30–60%; involvement of 1 to 4 joints; asymmetric large joints; risk for chronic uveitis in ANA positive females and axial skeletal involvement in older boys (1)[C]; types: (i) persistent (40%): knee, ankle, elbow; (ii) extended type (20%): >4 joints after first 6 months
  • Psoriatic arthritis: 5%; arthritis with psoriasis or arthritis with >2 of the following: dactylitis, nail changes (pitting), psoriasis in first-degree relative peaks age 2 to 4 years, and then again after age 10 years; HLA-B27 positive in 10–12%
  • Enthesitis-related arthritis: 1–11%; arthritis and/or enthesitis plus at least two of the following: sacroiliac or lumbosacral pain, Reiter syndrome or acute anterior uveitis in first-degree relative, acute symptomatic anterior uveitis, human leukocyte antigen HLA-B27 positive, history of ankylosing spondylitis, sacroiliitis with inflammatory bowel disease, onset of arthritis in male >6 years old
  • Undifferentiated arthritis (11–21%): presents with overlapping symptoms in ≥2 categories above or arthritis that does not fulfill above categories (1)[C]
• Systems affected: musculoskeletal, hematologic, lymphatic, immunologic, dermatologic, ophthalmologic, gastrointestinal
• Synonyms: juvenile chronic arthritis; juvenile arthritis; juvenile rheumatoid arthritis (JRA); Still disease (1)[C]

Epidemiology

54% of cases occur in children 0 to 5 years old.

Etiology and Pathophysiology

• Humoral and cellular immunodysregulation due to immune response toward a self-antigen; T lymphocytes play a key role.
• Environmental triggers, possibly infections: Rubella or parvovirus B19; heat shock proteins
• Immunoglobulin or complement deficiency

Risk Factors

Female sex 3:1

General Prevention

Maintain immunizations and infection prevention.

Commonly Associated Conditions

Other autoimmune disorders, chronic anterior uveitis, nutritional impairment, growth issues