Snapshot A 3-year-old boy presents to the emergency department due to worsening joint pain, fever, and a new rash. He is accompanied by his mother who reports that he has been pointing at his knee and hip while crying. She believes he has been having this symptom for approximately 2 months. He has been having 1-2 fevers a day, and she reports seeing a "pink-like" rash. On physical exam, there is an evanescent salmon-colored rash on the left thigh. There is tenderness to palpation of the left knee and hip with limited range of motion. Lab results show an elevated ESR, CRP, and positive ANA. A pediatric rheumatologist is consulted for further evaluation. Introduction Clinical definition a broad term that encompasses different types of pediatric chronic arthritis that is characterized by joint pain and inflammation 1 or more joints are involved for at least 6 weeks in patients < 16 years of age subtypes polyarticular juvenile idiopathic arthritis (JIA) ≥ 5 joints involved pauciarticular JIA 1-4 joints involved systemic JIA visceral involvement Epidemiology Incidence the most common chronic rheumatologic disorder in children Demographics more frequently with European ancestry ETIOLOGY Pathogenesis not well understood but may involve both genetic and environmental factors the humoral and cell-mediated immune system are involved T-cells release tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-1 the humoral immune system is involved by increasing antinuclear antibody (ANA) production, immunoglobulins, and circulating immune complexes Presentation Symptoms fever quotidian pattern fevers occurring once or twice per day that eventually subside morning stiffness and joint pain joint stiffness and pain can also be noted with prolonged periods of inactivity (e.g., sitting) visual changes can be suggestive of a uveitis Physical exam joint involvement swelling limited range of motion tenderness to palpation uveitis visceral involvement in cases of systemic JIA such as evanescent and salmon-colored macular rash hepatosplenomegaly serositis e.g., pleural and pericardial effusion Imaging Radiography indication performed if only 1 joint is involved in order to evaluate for other causes (e.g., osteomyelitis) Studies Labs ↑ c-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) typically in systemic and polyarticular JIA positive ANA in most cases Diagnostic criteria a patient < 16 years of age with 1 or more joints involved for at least 6 weeks Differential Reactive arthritis Rheumatoid arthritis Systemic lupus erythematosus Leukemia Pediatric sarcoidosis Still disease (in older patients) Adult-onset Still disease presents with arthritis, high fevers, and salmon-colored maculopapular rash Treatment Conservative period ophthalmologic exams indication for monitoring of eye involvement (e.g., uveitis) Medical nonsteroidal antiinflammatory drugs (NSAIDs) indication for symptomatic relief disease-modifying antirheumatic drugs (DMARD) indication for controlling inflammatory process medication methotrexate etanercept adalimumab intra-articular glucocorticoids indication effective in managing inflamed joint Complications Infection Macrophage-activation syndrome Pericarditis Hemolytic anemia Enarteritis Prognosis Postitive improved with advances in treatment Negative early hip or wrist involvement presence of rheumatoid factor