I am a vascular surgeon with a daughter who has been diagnosed with Juvenile Rheumatoid Arthritis. I know so little about this disease. Any information you can give me will be helpful. Thanking you in advance.

When most people think of arthritis they think of a disease of old people, but Juvenile Rheumatoid Arthritis (JRA) is a group of diseases that strikes the young. In fact, as we have learned more about how this differs from adult rheumatoid arthritis, pediatric rheumatologists have begun calling this Juvenile Idiopathic Arthritis (JIA). JIA is not rare. According to Dr. Sasha Bernatsky of Montreal General Hospital, up to 18 out of every 100,000 children develop JIA each year (Arthritis Care & Research. 57:1, 44-48).

JIA refers to a grab-bag of several distinct arthritis diseases. They can range from relatively mild conditions which disappear at puberty, to relentlessly progressive, crippling arthritis.

The exact cause of the arthritides in JIA remains unknown. The two leading theories are that the diseases are caused by infections with as-yet-unidentified microorganisms, or that the diseases are the result of an over-exuberant auto-immune reaction -- one's own immune system turning against oneself. Either way, some children inherit a genetic predisposition to JIA.

All forms of rheumatoid arthritis are characterized by chronic swelling and inflammation of the synovial membrane which lines joints. If this chronic inflammation continues over years, the joint cartilage and joint bone become eroded and are gradually destroyed. The amount of time the chronic inflammation can last before the damage becomes permanent varies a great deal, but it is a much longer period in Juvenile Idiopathic Arthritis compared to Adult Rheumatoid Arthritis. Many children with JIA outgrow the disease and never develop permanent joint damage, but others may battle the condition for a lifetime.

As stated earlier, there are five major sub-types of rheumatic disease that fall under the name JIA. Note that the names of these disorders and the criteria for diagnosis have changed in recent years, but that many doctors use the Durban Criteria for differentiating the types of JIAs. I imagine the names will continue to change, as we learn more about these conditions.

First, there is polyarticular (many-joint) rheumatoid arthritis. The great majority of children affected by this sub-type of JIA are girls. The polyarticular diseases are characterized by involvement of multiple joints, typically including the small joints of the hands. The polyarticular diseases comprise about 35% of children with JIA. There are two forms of the polyarticular disease differentiated by a blood test for an immune compound called the rheumatoid factor. Rheumatoid Factor Positive Polyarticular Disease tends to appear in late childhood and is the more severe of the two polyarticular diseases. Rheumatoid nodules often appear at the joints. Rheumatoid Factor Negative Polyarticular JIA may begin at any time in childhood and is typically mild. It is rarely associated with rheumatoid nodules at the joint spaces. The affected joints are typically swollen and warm. They tend to be particularly stiff and painful in the morning and following periods of inactivity. Joint involvement in both polyarticular diseases is typically symmetric, with both sides of the body mirroring each other.

The next group of diseases are called pauciarticular (few-joints) diseases. These are characterized by a joint involvement that is limited to four or fewer joints for the first six months of the disease. The large joints are primarily affected, and the arthritis is typically asymmetric.