|S: Systemic||Whole body is affected|
|J: Juvenile||Begins in childhood|
|I: Idiopathic||Cause is unknown|
|A: Arthritis||Joint inflammation|
SJIA is one of several rheumatic diseases that affect children. The whole body is affected, not just the joints (the S in the abbreviation stands for “systemic.”) SJIA is the rarest form of JIA.
SJIA is also called Still’s disease, after the doctor who first reported the illness.
There are seven forms of Juvenile Idiopathic Arthritis (JIA)
Other rheumatic diseases in children include joint inflammation caused by germs such as bacteria or viruses. These are referred to as “infectious” or “acute” arthritis, but not as “idiopathic” because the cause is known.
SJIA occurs worldwide. While we do not exactly know how frequently SJIA occurs, it is estimated that between 10% and 15% of all children with JIA have SJIA.
SJIA affects the entire body, including the joints. SJIA typically occurs in flares; so often healthy periods are alternated with illness. Diagnosis may be slowed down by these ups and downs over the course of the disease. During a flare-free interval, SJIA is harder to detect than during an acute flare.
The most common symptoms of SJIA are recurrent bouts of fever with daily peaks, red (or salmon pink) rash, and painful joint stiffness or inflammation.
An acute flair of SJIA (or an active phase) often looks like this:
|Swollen and painful joints|
|Enlarged internal organs|
The disease can still affect other areas of the body:
Possible symptoms of SJIA
Possible long-term consequences of SJIA are joint destruction, functional impairments and growth reduction.
Other possible complications of SJIA are macrophage activation syndrome (MAS) and amyloidosis:
Macrophage activation syndrome (MAS)
A serious complication of rheumatic diseases caused by activation and uncontrolled proliferation of the "eating cells" (macrophages) and other immune cells. It occurs in approximately 1 out of 10 patients with SJIA. It can lead to symptoms of blood poisoning and internal organ failure.
Deposition of proteins in kidneys, which can damage the kidneys. Improved diagnostics and treatment means that amyloidosis occurs less frequently than previously.
The disease course and severity of SJIA can be very different from child to child.
Possible disease courses of SJIA
SJIA is a condition of the innate immune system. Messengers called interleukins that promote the inflammatory response play a key role in the development of SJIA.
The other forms of JIA are autoimmune diseases, meaning that they involve antibodies of the acquired immune system.
It is unknown what triggers the autoinflammatory response in SJIA.
Doctors and scientists are still researching the causes of SJIA. It has been speculated that an infection could be the trigger; alternatively, there could be a genetic cause. New theories suggest there may be several factors causing SJIA.
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