What is juvenile idiopathic arthritis?

Juvenile idiopathic arthritis (JIA) is a chronic condition that causes inflammation in one or more joints and begins before the age of 16. There are several different patterns. 

Though they all have joint inflammation in common, they behave very differently, may require different treatment approaches, and have different outcomes. 

The main patterns of JIA are:

• Systemic JIA type begins with very high fevers, is often accompanied by a skin rash and shows evidence of inflammation in many internal organ systems as well as the joints. About 10% of children with arthritis have this type.
• Oligoarticular onset disease affects four or fewer joints. About half of all children with arthritis are in this category. Some are very young, from infancy to about five years old. As they are at risk of developing inflammatory eye problems called uveitis, regular eye exams are essential. Others are older and the disease may evolve and extend to involve more than four joints.
• Polyarticular JIA has more than four joints affected and can begin at any age. 
Some of these children have adult type rheumatoid arthritis and have a positive blood test for Rheumatoid Factor. 
• Enthesitis Related arthritis involves inflammation of the ligaments and tendons in the area where they attach to bone.  This subtype is more common in older boys and may progress to adult ankylosing spondylitis.
• Psoriatic JIA is seen in children with psoriasis and/or a family history of psoriasis. This may affect any number of joints. It has some specific characteristics, including the presence of “sausage digits” where a whole finger or toe may be swollen.

Revised and reviewed by Dr Chris Scott, Paediatric Rheumatologist, Red Cross Children’s Hospital, Cape Town February 2015.