Systemic-onset juvenile idiopathic arthritis

A subtype of juvenile idiopathic arthritis characterized by systemic symptoms

Systemic-onset juvenile idiopathic arthritis (SoJIA) is a subtype of juvenile idiopathic arthritis (JIA) that is distinguished by its systemic features, including fever, rash, and inflammation of internal organs, in addition to arthritis. It is a rare and complex condition that primarily affects children.

Clinical Features

Systemic-onset juvenile idiopathic arthritis is characterized by a combination of systemic and articular symptoms. The hallmark features include:

• Fever: Patients typically experience a daily fever that spikes once or twice a day, often reaching 39°C (102°F) or higher.
• Rash: A transient, salmon-colored rash may appear, often coinciding with fever spikes. The rash is usually non-itchy and can appear on the trunk and extremities.
• Arthritis: Joint inflammation is a key feature, affecting one or more joints. The arthritis can be persistent and may lead to joint damage if not adequately treated.
• Lymphadenopathy: Swollen lymph nodes are common.
• Hepatosplenomegaly: Enlargement of the liver and spleen may occur.
• Serositis: Inflammation of serous membranes, such as the pleura or pericardium, can lead to pleuritis or pericarditis.

Pathophysiology

The exact cause of systemic-onset juvenile idiopathic arthritis is unknown, but it is believed to involve a combination of genetic and environmental factors. The condition is thought to be an autoinflammatory disease, characterized by dysregulation of the innate immune system. Key cytokines involved in the inflammatory process include interleukin-1 (IL-1), interleukin-6 (IL-6), and interleukin-18 (IL-18).

Diagnosis

Diagnosis of SoJIA is primarily clinical, based on the characteristic symptoms and exclusion of other conditions. Laboratory tests may show elevated inflammatory markers such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Other tests may include:

• Complete blood count (CBC): May show anemia, leukocytosis, and thrombocytosis.
• Ferritin levels: Often elevated in SoJIA.
• Antinuclear antibody (ANA) and rheumatoid factor (RF): Typically negative in SoJIA.

Treatment

The management of systemic-onset juvenile idiopathic arthritis involves controlling inflammation and preventing joint damage. Treatment options include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs): Used to reduce pain and inflammation.
• Corticosteroids: May be used for rapid control of severe systemic symptoms.
• Disease-modifying antirheumatic drugs (DMARDs): Such as methotrexate, may be used for long-term management.
• Biologic agents: Targeted therapies such as IL-1 inhibitors (e.g., anakinra) and IL-6 inhibitors (e.g., tocilizumab) have shown efficacy in treating SoJIA.

Prognosis

The prognosis of systemic-onset juvenile idiopathic arthritis varies. Some children experience a monophasic course with complete resolution, while others may have a chronic or polycyclic course with persistent arthritis and systemic symptoms. Early and aggressive treatment can improve outcomes and reduce the risk of complications.

Related Pages

• Juvenile idiopathic arthritis
• Autoinflammatory disease
• Interleukin-1
• Interleukin-6