Juvenile Idiopathic Arthritis

Juvenile idiopathic arthritis (JIA) is a group of autoimmune disorders characterized by chronic arthritis in children under 16 years of age, leading to persistent joint inflammation, pain, stiffness, and potential growth abnormalities.

Definition

Juvenile idiopathic arthritis (JIA) is a group of autoimmune disorders characterized by chronic arthritis in children under 16 years of age, leading to persistent joint inflammation, pain, stiffness, and potential growth abnormalities.

Epidemiology

Most common chronic rheumatic disease in children
Prevalence: approximately 1 per 1,000 children
Peak onset between 1 and 6 years, but can occur in adolescence
Girls are more frequently affected than boys (2:1 ratio)
Incidence varies by subtype and geographic region

Etiology

Autoimmune-mediated inflammation of synovium
Genetic predisposition: HLA associations (e.g., HLA-DRB1, HLA-B27)
Environmental triggers: infections, trauma, or other immune stimuli
Dysregulated cytokine production (IL-1, IL-6, TNF-alpha)
No single causative agent identified; multifactorial etiology
Subtypes include oligoarticular, polyarticular, systemic, enthesitis-related, psoriatic

Pathophysiology

Chronic synovial inflammation leads to pannus formation
Destruction of cartilage and subchondral bone over time
Joint effusion and stiffness result from inflammatory mediators
Systemic manifestations (fever, rash, organ involvement) in systemic JIA
Altered growth hormone and cytokine effects may impair linear growth
Autoantibodies (ANA, RF) present in some subtypes
Chronic inflammation can lead to functional disability and deformities