Juvenile Rheumatoid Arthritis (Juvenile Idiopathic Arthritis)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Juvenile Rheumatoid Arthritis (JRA), also known as Juvenile Idiopathic Arthritis (JIA), is a chronic autoimmune disorder in children that causes persistent joint inflammation. It is characterised by joint pain, swelling, stiffness, and can affect children of all ages. JIA is the most common type of arthritis in children, and it can involve one or multiple joints. There are several subtypes of JIA, including oligoarticular, polyarticular, and systemic onset JIA.

Aetiology

The exact cause of JIA is not well understood, but it is believed to be due to a combination of genetic predisposition and environmental factors that trigger an autoimmune response. In JIA, the immune system mistakenly attacks the body’s own tissues, particularly the synovium (the lining of the joints), leading to inflammation. Some contributing factors include:

• Genetic susceptibility: Certain gene variations, such as those related to the HLA (human leukocyte antigen) system, may increase the risk of developing JIA.
• Environmental triggers: Viral or bacterial infections may act as triggers for the onset of JIA in genetically predisposed children.
• Autoimmune response: An abnormal immune response leads to inflammation and damage to the joints.

Pathophysiology

In JIA, the immune system targets the synovial membrane (synovium) in the joints, leading to inflammation. Over time, chronic inflammation can result in thickening of the synovium, accumulation of inflammatory cells, and release of cytokines. This leads to joint swelling, pain, and stiffness. If untreated, the chronic inflammation can damage the cartilage and bones within the joint, leading to joint deformity and loss of function.

JIA is a heterogeneous disorder with several subtypes, each with slightly different pathophysiological mechanisms:

• Oligoarticular JIA: Affects four or fewer joints, typically larger joints like the knees or ankles.
• Polyarticular JIA: Affects five or more joints, including smaller joints such as those in the hands and feet.
• Systemic JIA: Involves not only joint inflammation but also systemic symptoms such as fever, rash, and organ involvement.

Risk Factors

• Family history: A family history of autoimmune diseases or rheumatoid arthritis increases the risk of JIA.
• Gender: Girls are more commonly affected by certain types of JIA, such as oligoarticular and polyarticular JIA.
• Age: JIA can affect children of any age, but certain types tend to present in early childhood or adolescence.
• Genetic markers: Specific genetic markers, including HLA alleles, have been associated with an increased risk of JIA.

Signs and Symptoms

The symptoms of JIA can vary depending on the subtype, but common signs and symptoms include:

• Joint pain and swelling: Persistent pain, swelling, and tenderness in the affected joints, particularly after rest or in the morning.
• Stiffness: Stiffness in the joints, especially in the morning (morning stiffness), is a hallmark symptom.
• Fatigue: Children with JIA may feel tired or lethargic due to chronic inflammation.
• Fever: Children with systemic JIA may experience recurrent fevers, often accompanied by a salmon-coloured rash.
• Reduced range of motion: Limited mobility in the affected joints.
• Rash: Systemic JIA may present with a pink, salmon-coloured rash that comes and goes with fever.
• Eye inflammation (uveitis): Inflammation of the eye (uveitis) can occur, particularly in oligoarticular JIA, and may lead to vision problems if untreated.

Investigations

The diagnosis of JIA is based on clinical findings and laboratory investigations to rule out other causes of joint inflammation:

• Full blood count (FBC): May show anaemia of chronic disease, leukocytosis, or thrombocytosis in systemic JIA.
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP): Elevated in cases of active inflammation.
• Antinuclear antibodies (ANA): Positive in some children, particularly those with oligoarticular JIA, and may indicate a risk of uveitis.
• Rheumatoid factor (RF): Positive in some cases of polyarticular JIA, although most children are RF-negative.
• Imaging: X-rays or MRI may be used to assess joint damage and inflammation.
• Eye examination: Regular eye exams are necessary to detect uveitis in children with JIA.

Management

The management of JIA focuses on reducing inflammation, relieving pain, maintaining joint function, and preventing complications. Treatment is tailored to the specific subtype and severity of the disease:

Medications:

• Nonsteroidal anti-inflammatory drugs (NSAIDs): First-line treatment for pain and inflammation relief.
• Disease-modifying antirheumatic drugs (DMARDs): Methotrexate is commonly used to slow disease progression and control inflammation.
• Biologic agents: For children with more severe or refractory JIA, biologic therapies such as tumour necrosis factor (TNF) inhibitors (e.g., etanercept, adalimumab) may be used to target specific immune pathways.
• Corticosteroids: Used for short-term control of severe inflammation, particularly in systemic JIA or during flare-ups.
• Intra-articular steroid injections: May be used to directly reduce inflammation in affected joints.

Physical Therapy and Occupational Therapy:

• Physical therapy is essential to maintain joint mobility, muscle strength, and overall function.
• Occupational therapy helps children with JIA manage daily activities and adapt to joint limitations.

Regular Monitoring and Follow-up:

• Children with JIA require regular follow-up appointments to monitor disease activity, adjust treatment, and assess for complications such as uveitis or joint damage.

References

1. NICE (2024). Juvenile Idiopathic Arthritis: Diagnosis and Management. Available at: NICE Guidance
2. Royal College of Paediatrics and Child Health (2023). Juvenile Idiopathic Arthritis Overview. Available at: RCPCH
3. British Society for Paediatric and Adolescent Rheumatology (2023). Management of Juvenile Idiopathic Arthritis. Available at: BSPAR