Juvenile arthritis is a disease in which there is inflammation (swelling) of the synovium in children aged 16 or younger. The synovium is the tissue that lines the inside of joints.
Juvenile arthritis is an autoimmune disease. That means the immune system, which normally protects the body from foreign substances, attacks the body instead. The disease is also idiopathic, which means that no exact cause is known. Researchers believe juvenile arthritis may be related to genetics, certain infections, and environmental triggers.
Rheumatoid arthritis (RA) is a painful inflammatory disease that causes swelling, stiffness, joint destruction, and deformity. This autoimmune disease has an effect on the cells that coat and lubricate joints (synovial tissue).
Osteoarthritis (the "wear and tear" arthritis") may often affect just one joint even though it can affect multiple joints. Rheumatoid arthritis, though, typically affects multiple joints and usually happens symmetrically. For instance, RA may affect the same joint...
Because a child may have no symptoms of juvenile arthritis, and because some of the symptoms can be associated with other diseases, a diagnosis may be difficult. Because there is no actual test for juvenile arthritis, the diagnosis is made by excluding other conditions that may cause similar symptoms, such as bone disorders or breaks, fibromyalgia, infection, Lyme disease, lupus, or cancer.
The doctor is likely to begin by taking a complete medical history and performing a complete medical exam. Additional testing might be useful in determining what type of arthritis the child has. Some of the other tests that might be ordered include:
Bone marrow exam, which is used to check for leukemia
Erythrocyte sedimentation rate to see how quickly the red blood cells fall to the bottom of a test tube (The rate is faster in most people who have a disease that causes inflammation.)
Test for rheumatoid factor, an antibody that may be found in people with arthritis (An abnormal result is more common in adults than in children.)
Antinuclear antibody test to show evidence of autoimmunity (Autoimmunity is a disease state in which the body's defense system, the immune system, malfunctions and attacks the body itself. This test is also useful in predicting if eye disease will develop in children with juvenile arthritis.)
Bone scan to detect changes in bones and joints (This test may be ordered if the symptoms include unexplained pain in the joints and bone.)
Joint fluid sampling and synovial tissue sampling, which might be performed by an orthopedic surgeon