About JIA

Juvenile Idiopathic Arthritis (JIA) is an autoimmune disorder where the body’s natural defences (designed to stop infections) start to attack the joints. This causes to inflammation of the joints, leading to pain, discomfort and reduced mobility.

‘JIA’ means:

Juvenile – the arthritis began before the age of 16. When a young person with JIA turns 16, they still have ‘JIA’ because the condition is different from adult types of arthritis.

Idiopathic – means that the cause is unknown.

Arthritis – means that one or more joints are inflamed, usually for at least six weeks.

JIA is usually diagnosed by a specialist paediatric rheumatologist. This is a doctor who is trained in conditions like JIA. At the first assessment, the doctor will check each joint for inflammation and range of movement to see how many joints are affected. Each time you then return to the doctor, they will check the joints again to see how things have changed.

JIA does not only affect the joints. Quite often, the eyes can also be inflamed – a condition known as uveitis. If you are diagnosed with JIA, it is very important you get your eyes checked urgently for uveitis as it can lead to permanent sight loss. More information about uveitis is available from Olivia’s Vision.

There are different types of JIA:

Oligoarthritis (sometimes known as oligoarticular arthritis, or simply ‘oligo JIA’)

In this type of JIA, four or fewer joints are involved during the first six months. In some cases, it may spread to other joints (then called ‘extended oligoarthritis’).

Polyarthritis (sometimes known as polyarticular arthritis, or simply ‘poly JIA’)

This type of JIA means five or more joints are involved during the first six months. Some of the joints involved may be the small joints in the hands and feet. Some patients with this type of arthritis have a marker in their blood called ‘Rheumatoid Factor’, or ‘RF’. Children and young people who are RF-positive (sometimes shown as RF+) usually find their JIA is more like adult-onset Rheumatoid Arthritis. All other types of JIA, including RF-negative poly JIA, are very different from the adult condition.


Systemic JIA usually causes a high non-contagious fever and a rash, which most often appears on the trunk, arms and legs. The disease can also affect internal organs, such as the heart, liver, spleen and lymph nodes.


This type of JIA is characterized by the inflammation of the entheses, or sites where tendons attach to the bone.

Psoriatic arthritis

This type of arthritis affects young people who have arthritis with the rash of psoriasis.

Around 1 in every 1,000 children and young people under the age of 16 have JIA. That is around 15,000 children in the UK alone.

At present, there is no cure for Juvenile Idiopathic Arthritis. All current treatments seek to reduce the symptoms of JIA, but are not a cure. Whilst these treatments have beneficial effects in reducing pain and inflammation, and provide some protection against long-term joint damage, they come with their own side-effects and impinge on long-term health of children taking these medications. In around half of all cases, children go into spontaneous remission. But in the other half, they are confined to taking powerful drugs long-term, with all the side-effects and complications that causes.

If you would like to know more about JIA, including information about the medications and treatments currently available, you may be interested in The Centre for Adolescent Rheumatology, within the Institute of Child Health – visit http://www.centre-for-adolescent-rheumatology.org. Please remember to speak to your doctor in the first instance if you have any questions about your treatment and medicines.

We have produced a glossary of some of the key terms about JIA.

We are Juvenile Arthritis Research (JAR). JAR is a non-profit project seeking to find a cure for JIA, raising awareness that children and young people get arthritis, and providing support to children with JIA and their families. Find out more about us and our aims. If you would like to support our work, click here.