Systemic-onset juvenile idiopathic arthritis
A systemic autoinflammatory arthritis with fever, rash, and organ involvement.
Systemic-onset juvenile idiopathic arthritis (sJIA)—also called Still disease or systemic juvenile idiopathic arthritis—is a form of juvenile idiopathic arthritis (JIA) marked by arthritis, a distinct red skin rash, and fevers that come and go. It is classified as an autoinflammatory condition, not an autoimmune disease, and its cause remains unknown. A genetic predisposition may be involved, but no single infectious agent has been identified despite testing.
Children with sJIA are often quite ill when first diagnosed. They may have lost weight, feel tired, run a fever, and experience muscle and joint pain, along with occasional chest or stomach discomfort. These symptoms can overshadow the arthritis early on. Fever is nearly universal at presentation, with a characteristic pattern: body temperature spikes above 39°C once or twice daily, then drops quickly to normal or below.
More than 80% of patients develop a salmon-colored rash made up of flat or slightly raised spots that appears with the fever. Less commonly, the rash may be hives-like. It usually shows up on the trunk, neck, and upper arms and legs, but can spread further. The spots are typically less than 5 millimeters across, though larger ones may occur with fading centers. The redness can vary in the same person, and the rash tends to move around and does not itch.
Arthritis must be confirmed to meet diagnostic criteria, but it may not be obvious at first. Joint pain is common early on, yet arthritis can appear weeks, months, or even years later. Joint involvement ranges widely—from many joints to just four or fewer. The wrists, knees, and ankles are most often affected, but any joint can be involved, including the jaw, neck, hips, and small joints of the hands and feet. Muscle pain and inflammation of tendon sheaths are also common.
Enlargement of the spleen and lymph nodes is typical in sJIA, occurring separately or together. Lymph nodes in the front of the neck, armpits, and groin are often noticeably swollen, firm, movable, and not tender. Splenomegaly, seen in fewer than 10% of patients, usually appears within the first few years and can be severe.
The lining around the heart is frequently involved. In one study, 81% of children with active systemic symptoms had abnormal echocardiogram findings, and 36% had fluid buildup or thickening of the pericardium.
Quick Facts
- Specialty
- Pediatrics, rheumatology
- Symptoms
- Fever, arthritis, rash, and lymphadenopathy.
- Complications
- Macrophage activation syndrome.
- Onset
- 1-5 years old.
- Diagnosis
- Excluding other disorders and clinical criteria.
- Differential
- Septic arthritis, osteomyelitis, postinfectious arthritis, multisystem inflammatory syndrome in children, malignancy, and other autoimmune and autoinflammatory diseases.
- Treatment
- NSAIDs, biologic agents
- Medication
- Anakinra, canakinumab, rilonacept, and tocilizumab.
Facts from the source article.
Lore & Background
SJIA is characterized by splenic and lymph node enlargements, with prominent symmetrical lymphadenopathy in the anterior cervical, axillary, and inguinal regions. Pericardial involvement is common; one study found 81% of children with active systemic symptoms had abnormal echocardiographic findings, and 36% had an effusion or pericardial thickening. Around one-third of children with sJIA have occult macrophage activation syndrome (MAS), a potentially fatal condition causing a 'cytokine storm' from rapid T cell and macrophage activation. MAS can present with persistent fever, fixed rash, myocarditis, renal failure, hepatic dysfunction, and coagulopathy.
Reader's Guide
Systemic-onset juvenile idiopathic arthritis represents a significant subtype of juvenile idiopathic arthritis, accounting for 10% to 20% of cases and affecting 1 to 4 out of every 1000 children. Its diagnosis is clinical and one of exclusion, requiring thorough evaluation for infection and cancer, including blood and urine cultures, imaging, and bone marrow exams. The International League of Associations for Rheumatology criteria include arthritis, at least 2 weeks of daily fever, and symptoms such as organomegaly, lymphadenopathy, serositis, or evanescent rash. Treatment varies based on involvement and presence of MAS; nonsteroidal anti-inflammatory drugs provide analgesic and antipyretic effects, while clinical trials show anti-interleukin-6 and anti-interleukin-1 drugs effectively manage systemic symptoms. Studies indicate 40% of children have a monocyclic disease course, recovering after varying periods, while over half experience a prolonged course. The autoinflammatory nature of sJIA, driven by innate immune system dysfunction and cytokines like interleukin-1 and interleukin-6, distinguishes it from autoimmune diseases and guides therapeutic approaches.
Did You Know?
- Over 80% of patients have a salmon-colored macular or maculopapular rash that is migratory and nonpruritic.
- Pericardial involvement is common, with 81% of children with active systemic symptoms having abnormal echocardiographic findings.
- The cause of sJIA is unknown; it is considered an autoinflammatory condition, not an autoimmune disease.
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