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KEY POINTS
■ Juvenile idiopathic arthritis (JIA) is arthritis of unknown etiology that must be diagnosed by age 16 years. Symptoms must be present for at least 6 weeks.
■ JIA has five subtypes: oligoarticular, polyarticular, systemic, enthesitis-related, and psoriatic arthritis. Each subtype has varying
presentations and lifelong sequelae.
■ Joint swelling and gait disturbances are strongly correlated presenting complaints in patients with JIA. Laboratory values are not
specific and serve only a supportive role in diagnosis.
■ Treatment may include exercise therapy, NSAIDs, corticosteroids, disease-modifying antirheumatic drugs, tumor necrosis factor
blockers, and even surgery. Many new treatments are currently under investigation, including interleukin receptor antagonists.
Juvenile idiopathic arthritis (JIA)—also known as
juvenile rheumatoid arthritis (JRA), although JRA is now an outdated term—is considered the most common rheumatic disease in children younger than 16 years.1 The condition has a wide variety of manifestations, often making it difficult to identify. A timely diagnosis is important because JIA may cause significant short- and long-term disability. Since the diagnosis is clinical—a diagnosis of exclusion—practitioners who maintain a high index of suspicion are more likely to recognize JIA early.
Juvenile idiopathic arthritis is defined as arthritis of unknown etiology with symptoms that persist for at least 6 weeks. The condition is diagnosed before age 16 years, and its symptoms cannot meet the diagnostic criteria for other known conditions. Several classifications and presentations of the disorder exist, and treatment varies. JIA may persist into adulthood, and in these cases, clinicians should be prepared to provide long-term care and should consider likely comorbidities.
DIAGNOSTIC CATEGORIES
The classification criteria developed by the International League of Associations for Rheumatology is the most frequently used system to diagnose juvenile idiopathic arthritis (Table 1). This system identifies five major subtypes of the condition, and an undifferentiated arthritis category if criteria for multiple subtypes or no subtypes are met. Factors common to all the subtypes include joint swelling and gait disturbances.2
Juvenile idiopathic arthritis is the most common systemic disease associated with uveitis in childhood, so patients often present with both conditions. Anterior uveitis may occur in patients with all subtypes of JIA who have a positive serum antinuclear antibody (ANA) test result but is most common with oligoarticular JIA.3 Uveitis is initially asymptomatic with permanent damage occurring at the onset of symptoms, so JIA patients benefit from an ophthalmologic consultation.
Oligoarthritis Up to four joints may be affected at diagnosis; the disease is said to be extended if it progresses to affect more than four joints after the first 6 months and to be persistent if not more than four joints are affected throughout the course of the disease. The large joints of the lower extremities (the knees and ankles) are most likely to be affected.1 Oligoarthritis is the most common presentation of juvenile idiopathic arthritis.2
Polyarthritis This classification includes rheumatoid factor (RF)-negative or RF-positive arthritis involving five or more joints in the first 6 months of disease. Two or more positive RF test results at least 3 months apart in the first 6 months are required for disease to be classified as RF-positive JIA.2
Systemic-onset juvenile idiopathic arthritis (soJIA) Also known as Still disease, soJIA is defined as 6 weeks of arthritis with intermittent fever that spikes daily or twice daily, usually each evening, for at least 2 weeks. Other symptoms must include at least one of the following: characteristic evanescent erythematous rash, generalized lymphadenopathy, organomegaly, and serositis. Laboratory findings not required for classification may include neutrophilia, thrombocytosis, and mild anemia, as well as an elevated ESR and elevated levels of C-reactive protein (CRP), liver transaminases, serum ferritin levels, D-dimers, and aldolase. The pattern of arthritis is split equally between oligoarticular and polyarticular, most frequently involving the knee, wrist, and ankle. The sacroiliac joint is least often involved.2 No significant sex bias has been identified in this subtype, and the age at diagnosis peaks at ages 0 to 5 years, with 2 years being the most common.4
Psoriatic and enthesitis-related arthritis Less common diagnoses include arthritis and enthesitis with two of the following symptoms: sacroiliac (SI) joint tenderness; presence of HLA-B27 antigen; onset of arthritis in a male older than 6 years; acute uveitis or history of ankylosing spondylitis; or sacroiliitis with inflammatory bowel disease, Reiter syndrome, or acute anterior uveitis in a first-degree relative. Psoriatic arthritis is arthritis and psoriasis with two of the following: dactylitis, nail pitting, or a first-degree relative with psoriasis.2