When Rheumatoid Arthritis Strikes Young
When rheumatoid arthritis strikes before age 16, it's called juvenile rheumatoid arthritis. Its newer name is juvenile idiopathic arthritis (JIA). Although JIA can happen any time after infancy, the most common time it develops is between 2 and 3 years of age. In adults, RA usually strikes in middle age.
Both adult RA and JIA are autoimmune diseases. That means the immune system mistakes normal parts of the body for foreign invaders and attacks them. The attacks cause swelling and pain, called inflammation. The most common part of the body attacked in JIA is the lining inside joints, the synovium.
Types of JIA
In adults, RA usually starts with joint pain and morning stiffness. But with JIA, the symptoms depend on what type of JIA a child has. There are three main types:
Oligoarticular JIA. This is the most common type of JIA, responsible for about 60% of the cases of children with JIA. Oligoarticular JIA affects fewer than four joints, usually big joints like the knees, ankles, and elbows. This type of JIA may also attack the eyes, causing redness and pain. It is more common in girls and usually starts before age 5.
Polyarticular JIA. This type of RA affects more than four joints as well as smaller joints, like the joints in the hands and feet. About 20% of children with JIA have this type.
Systemic JIA. Systemic means it affects the whole body. Only 10% of children with JIA (also known as Still’s disease) have the systemic type, boys and girls equally. It affects small joints and can lead to swelling in internal organs. It also can cause a decrease in red blood cells and an increase in white blood cells. A youngster may get a high fever and a rash weeks or months before joint symptoms start.