Juvenile Idiopathic Arthritis (JIA) is a chronic condition causing joint inflammation in children under 16. It is the most common rheumatic disease affecting children, lasting for at least six weeks. JIA is an autoimmune condition where the body’s immune system mistakenly attacks its own healthy tissues, specifically the joints. Polyarticular JIA is a distinct subtype.
Defining Polyarticular Juvenile Idiopathic Arthritis
Polyarticular JIA is characterized by arthritis affecting five or more joints, both large and small, often in a symmetrical pattern, within the first six months of disease onset. It is the second most common form of JIA, following oligoarticular JIA.
Polyarticular JIA is categorized by the presence or absence of rheumatoid factor (RF). Rheumatoid factor-positive polyarticular JIA affects about 5% to 8% of children with JIA and often occurs in children over 10 years old, resembling adult rheumatoid arthritis more closely. It commonly involves small joints of the hands and feet, and larger joints like the knees, hips, and ankles, often symmetrically.
Conversely, rheumatoid factor-negative polyarticular JIA accounts for about 15% to 20% of JIA cases. This form can appear at any age, with a higher occurrence in females. It can begin in many joints simultaneously, often symmetrically, or start in a few joints and spread to others within the first six months.
Recognizing the Symptoms
Children with polyarticular JIA typically experience joint pain, swelling, and stiffness. Stiffness is often most noticeable in the morning or after periods of rest, making movement difficult. Affected joints may also feel warm to the touch and appear discolored.
Beyond joint-specific symptoms, polyarticular JIA can present with systemic features. These may include a low-grade fever (generally less than 38.5 degrees Celsius or 101.5 degrees Fahrenheit), fatigue, reduced appetite, and mild weight loss or slow growth.
Less common systemic symptoms include mild lymph node enlargement or anemia. While complications affecting the heart or lungs are rare, inflammation can sometimes affect the lining of these organs. Symptoms can fluctuate, with periods of worsening (flare-ups) and improvement (remission).
Diagnostic Process and Treatment Strategies
Diagnosing polyarticular JIA involves a comprehensive approach, as there is no single test to confirm the condition. A healthcare provider begins with a detailed medical history and physical examination to assess joints for swelling, pain, and limited range of motion. This evaluation helps rule out other conditions that can mimic JIA.
Blood tests are used to check for markers of inflammation such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Tests for rheumatoid factor (RF) and antinuclear antibodies (ANA) are also performed to help classify the JIA subtype and assess the risk of certain complications, such as eye inflammation. Imaging studies, including X-rays, ultrasound, bone scans, or MRI, visualize joint damage.
Treatment for polyarticular JIA aims to reduce inflammation, manage pain, preserve joint function, and prevent long-term damage. Medications are a key component and include nonsteroidal anti-inflammatory drugs (NSAIDs) for initial symptom relief. Disease-modifying anti-rheumatic drugs (DMARDs), such as methotrexate, are used to slow disease progression and suppress the immune system. Biologic agents, which target specific inflammatory pathways, are also used, alone or in combination with DMARDs.
Physical and occupational therapy are integral to maintaining joint movement and muscle strength. Therapists recommend tailored exercises, protective equipment, or splints to support joints and help children remain active. Due to the potential for eye inflammation (uveitis), particularly in RF-negative polyarticular JIA with ANA positivity, regular eye exams by an ophthalmologist are an essential part of ongoing care.
Life with Polyarticular JIA
Living with polyarticular JIA involves ongoing management and a multidisciplinary care approach. Adherence to prescribed treatment plans, including medications and therapies, is important for controlling disease activity and preventing joint damage. Regular monitoring by a pediatric rheumatologist is necessary to adjust treatments and assess for potential complications.
Many children experience periods of remission, where symptoms lessen or disappear. Some children may achieve permanent remission. However, about half of patients may have active arthritis that persists into adulthood, requiring continued care.
The condition can impact daily activities, school attendance, and emotional well-being due to pain, fatigue, and limitations in movement. A care team, often including pediatric rheumatologists, physical therapists, occupational therapists, and ophthalmologists, works together to support the child and family. This collaborative approach helps address physical and emotional challenges.