|S: Systemic||Whole body is affected|
|J: Juvenile||Begins in childhood|
|I: Idiopathic||Cause is unknown|
|A: Arthritis||Joint inflammation|
SJIA (systemic juvenile idiopathic arthritis) is one of several rheumatic diseases that affect children. It usually affects children aged 5 years or younger.[1–3] The whole body is affected, not just the joints (hence the S in the name of the condition stands for “systemic.”) SJIA is the rarest form of juvenile idiopathic arthritis (JIA). ‘Juvenile’ means ‘childhood’ and ‘idiopathic’ means that the cause or trigger for the disease is not known.
SJIA is also called Still’s disease, after the doctor who first reported the illness. Some also refer to it as “Still’s syndrome”
There are seven forms of 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 in these cases the cause is known.
SJIA occurs worldwide. Exact data on how common it is are still being determined. In Europe it is estimated that each year, less than one child per 100,000 develops SJIA. The number of all people who currently have SJIA is estimated to be between 5 and 15 people in every 100,000.[6–8]
SJIA affects the entire body, including the joints. SJIA typically occurs in flares with some patients having healthy periods between flares. Diagnosis may be delayed by these ups and downs over the course of the disease. SJIA is generally easier to diagnose during a flare.
The most common symptoms of SJIA are recurrent bouts of fever with high daily temperature spikes, skin rash, and painful, stiff joints.[4,5,9]
An acute flare of SJIA (or an active phase) often looks like this:
|Swollen and painful joints|
|Enlarged internal organs|
The disease can also affect other areas of the body including the heart and lungs:
Possible symptoms of SJIA (modified according to [4,5,9])
Possible long-term consequences of SJIA are joint damage, loss of mobility and slowing of growth.[4,5] Approximately 4 out of 10 of children with SJIA have a lower body height than healthy children do.
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 multiplication of the "eating cells" (macrophages) and other immune cells. It occurs in approximately 1 out of 10 patients with SJIA[5,11–13]
A condition in which there is an abnormal build-up of a protein called amyloid in the kidneys that can lead to kidney failure.
Improved diagnostics and treatment means that kidney damage caused by amyloidosis-occurs less frequently than in the past.
The disease course and severity of SJIA can be very variable.[2,15,16] As shown in the diagrams below, there can be just a single episode of illness, repeated bouts of illness or, in the worst cases, constant illness.
Possible disease courses of SJIA (modified according to [2, 15, 16])
SJIA is a condition of the innate immune system. Chemical messengers called interleukins that promote the inflammatory response play a key role in the development of SJIA.
It is unknown what triggers the autoinflammatory response in SJIA but it has been suggested that an infection could be the trigger; alternatively there could be a genetic cause. New theories suggest there may be several factors working together (‘multifactorial’) that cause SJIA to develop.
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