Juvenile Rheumatoid Arthritis (JRA) is a group of diseases affecting children and adolescents younger than 16 years of age. It is the most common rheumatologic condition that occurs in childhood. Like rheumatoid arthritis (RA) that develops in adults, these diseases affect one or more joints in the body, causing them to become inflamed and damaged. JRA is an autoimmune disease, meaning that the body’s immune system produces proteins called autoantibodies that attack and destroy its own cells instead of protecting them. The autoantibodies involved in JRA particularly like attacking the joints, causing pain and swelling in those areas.
Continued inflammation of the joints may eventually cause these joints to be irreversibly destroyed. Fluid can develop inside these joints. The cartilage within the joints can be eroded away. The bones themselves may become deformed. However, depending on the type of JRA, parts of the body other than the joints may be affected as well.
What causes juvenile rheumatoid arthritis?
The exact cause of JRA is not known. Some diseases or conditions are thought to trigger an autoimmune reaction in the body, causing the body to produce autoantibodies that attack the synovium, which is connective tissue lining the inside surfaces of the joint. This causes the synovium to grow and thicken, pushing against the joint’s cartilage and bone. The damage may progress to include muscle and tendons attached to the joint.
Conditions that may trigger the development of JRA are:
- Trauma, including injury to the joint itself
- Infections such as septic arthritis and rheumatic fever
- Having a pet with enteritis
- Lyme disease
What are the signs and symptoms of juvenile rheumatoid arthritis?
Some signs and symptoms of JRA depend on the particular type of JRA involved. The severity of the symptoms also varies from child to child. However, listed below are symptoms that are common to most JRA patients:
- Joint pain and swelling
- Joint stiffness: the stiffness is more noticeable in the morning, especially upon waking up. Many parents of children with JRA report observing that their child moves slowly or with difficulty at the start of the day, but improves as the day goes on.
- Difficulty in joint movement: the pain and swelling may make it hard for the child to move the involved joint. The child may have a hard time straightening out or bending the joint. If the disease progresses, the child may have symptoms severe enough to cause him or her to walk with a limp.
- Problems with growth and development: JRA may affect the growth of only one joint, causing one limb to be shorter than the other. Children with JRA may also have less overall growth, causing them to be shorter than healthy children. The disease may also cause joints and bones to develop in an abnormal way, or become deformed.
- Eye inflammation: one or both eyes may be red, irritated, or painful. Vision may also be affected.
- Muscle pain
- Rashes
- Recurring fevers
- Decreased appetite and weight loss
What are the types of juvenile rheumatoid arthritis?
There are three diseases that fall under JRA: pauciarticular juvenile rheumatoid arthritis, polyarticular juvenile rheumatoid arthritis, and systemic juvenile rheumatoid arthritis.
Pauciarticular JRA (oligoarthritis), the most common type, is a disease that involves four joints or less. The joints affected are usually large joints (hips, knees, and ankles). This type of JRA can cause children to walk with a limp. Although the joints may become very swollen, many patients with pauciarticular JRA do not complain of pain. In most patients, symptoms are very mild. However, pauciarticular JRA can lead to some serious complications.
With pauciarticular JRA, patients have a high risk of developing eye inflammation, especially a condition known as iridocyclitis. This condition, if left untreated, can cause visual impairment or even permanent blindness. For patients with pauciarticular JRA, it is very important to have regular eye check-ups with a pediatric ophthalmologist.
Growth problems may also occur with pauciarticular JRA. This type of JRA tends to affect joints in an asymmetrical fashion (for example, it may affect only the right knee). This causes the leg bones in the unaffected side of the body to grow at a faster rate. Again, regular check-ups are important to monitor the growth of your child. If there is a difference between the lengths of your child’s legs, your doctor can suggest several options to correct the problem.
Polyarticular JRA (polyarthritis) affects five or more joints, usually the small joints such as those in the hands and feet). However, large joints may also be affected. The joints are involved in a symmetrical fashion—that is, if one joint on the right side is affected, its counterpart on the left is most likely affected as well. This type of JRA tends to get worse as time goes by.
Systemic onset JRA (Still’s disease) starts out by affecting parts of the body other than the joints. Instead of seeing joint problems, the child may at first have fever and rashes. The body temperature may spike to a very high temperature once or twice a day, then return to normal, only to have the fever develop again later on. The inflammation affects the membranes covering the lungs or the heart, and may also involve the liver or spleen.