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SJIA: Systemic juvenile idiopathic arthritis

What is SJIA?


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.

Childrens rheumatism

SJIA is also called Still’s disease, after the doctor who first reported the illness.

There are seven forms of Juvenile Idiopathic Arthritis (JIA)

Childrens rheumatism diagram

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.

How common is SJIA?

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.

What are the symptoms?

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:


  • Lasting longer than 2 weeks
  • Recurs daily in the early morning or afternoon
  • Sickness
  • Rash or a few red spots during periods of fever
Swollen and painful joints
  • May occur after rash and fever
Enlarged internal organs
  • Lymph nodes, liver and spleen are often enlarged


The disease can still affect other areas of the body:

Possible symptoms of SJIA diagram

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.


What typically happens over the course of the illness?

The disease course and severity of SJIA can be very different from child to child.

Possible disease courses of SJIA diagram

Possible disease courses of SJIA diagram

Possible disease courses of SJIA

What causes 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.


1. About Kids Health. Systemic Juvenile Idiopathic Arthritis (SJIA).
Accessed January 13, 2017.
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3. Dewitt EM, Kimura Y, Beukelman T et al. Arthritis Care & Research. 2012; 64(7):1001–1010.
4. Frosch M, Roth J. Rheumatology. 2008; 47 (2): 121–5.
5. Sawhney S, Woo P, Murray K. Arch Dis Child 2001; 85: 421–6.
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8. Juvenile Idiopathic Arthritis. Available from Accessed January 19, 2017.

Wondering how your life will change?

If you or your child has a rare disease, your life may look a little different than other people’s, and you may face added challenges or worries.  We’ve gathered some information and articles here that may help address a few of these. 

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