Related concepts:

Juvenile rheumatoid arthritis, JRA, Juvenile Idiopathic Arthritis, JIA

Introduction to Juvenile Idiopathic Arthritis:

When most people think of arthritis, they think of a disease common in old people, but Juvenile Rheumatoid Arthritis (JRA) is a group of diseases that strikes the young. In recent years, to better describe the many types of arthritides included in this group, the International League of Associations for Rheumatology (ILAR) renamed the disease Juvenile Idiopathic Arthritis (JIA) and most pediatric rheumatologists now prefer this new term.

What is Juvenile Idiopathic Arthritis?

JIA refers to a grab bag of at least five distinct arthritis diseases with at least seven patterns of illness. They can range from relatively mild conditions that 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 autoimmune reaction -- one's own immune system turning against oneself.

Who gets Juvenile Idiopathic Arthritis?

Some children inherit a genetic predisposition to JIA.

As stated earlier, there are at least five major subtypes of rheumatic disease that fall under the name JIA. Various organizations have developed their own classification schemes to subtype the arthritides. In general, the types of arthritis seen in JIA can be divided into polyarticular (affecting many joints), oligoarticular (affecting few joints), or systemic. They can also be divided based on whether or not the child has Rheumatoid Factor in the blood (RF positive or negative); whether they have antibodies called antinuclear antibody in the blood (ANA positive or negative); or if they carry a gene called HLA-B27.

What are the symptoms of Juvenile Idiopathic Arthritis?

All forms of rheumatoid arthritis are characterized by chronic swelling and inflammation of the synovial membrane that lines the joints. If this chronic inflammation continues over many 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 JIA compared to Adult Rheumatoid Arthritis. Many children with JIA outgrow the disease and never develop permanent joint damage.

The polyarticular diseases are characterized by involvement of multiple joints, typically including the small joints of the hands. Rheumatoid Factor Positive Polyarticular Disease tends to be the more severe of the two polyarticular diseases. Rheumatoid nodules often appear at the joints. Rheumatoid Factor Negative Polyarticular JRA 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.