JUVENILE RHEUMATOID ARTHRITIS
Juvenile rheumatoid arthritis (JRA) is a different form of arthritis that causes joint inflammation and stiffness for more than six weeks in a child of 16 years of age or less. Inflammation causes redness, swelling, warmth, and soreness in the joints, although many children with JRA do not complain of joint pain. Any joint can be affected, and inflammation may limit the mobility of affected joints. Doctors classify three kinds of JRA by the number of joints involved, the symptoms, and the presence or absence of specific antibodies in the blood. (Antibodies are particular proteins made by the immune system.) These classifications help the doctor determine how the disease will progress.
PAUCIARTICULAR
Pauciarticular means that four or fewer joints are affected. Pauciarticular is the most common form of JRA; about half of all children with JRA have this type. The pauciarticular disease typically affects large joints, such as the knees. Girls under the age of are most likely to develop this type of JRA.
Some children have particular proteins called antinuclear antibodies (ANAs) in the blood. Eye disease affects about 20 to 30 per cent of children with pauciarticular JRA. Up to 80 per cent of those with eye disease also test positive for ANA, which tends to develop at an exceptionally early age in these children. Regular examinations by an ophthalmologist (a doctor who specializes in eye diseases) are necessary to prevent serious eye problems such as iritis (inflammation of the iris) or uveitis (inflammation of the inner eye or uvea). Many children with pauciarticular disease outgrow arthritis by adulthood, although eye problems can continue, and joint symptoms may recur in some people.
POLYARTICULAR
About 30 per cent of all children with JRA have polyarticular disease. In polyarticular disease, five or more joints are affected. The small joints, such as those in the hands and feet, are most commonly involved, but the condition may also affect large joints. Polyarticular JRA often is symmetrical; that is, it affects the same joint on both sides of the body. Some children with polyarticular disease have an IgM rheumatoid factor (RF) antibody in their blood. These children often have a more severe form of the disease, which doctors consider to be the same as adult rheumatoid arthritis.
SYSTEMIC
Besides joint swelling, the systemic form of JRA is characterized by fever and a light pink rash and may also affect internal organs such as the heart, liver, spleen and lymph nodes. Doctors sometimes call it Still’s a disease—almost all children with this type of JRA test negative for both RF and ANA. The systemic form affects 20 per cent of all children with JRA. A small percentage of these children develop arthritis in many joints and can have severe arthritis that continues into adulthood.
JRA is an autoimmune disorder, meaning the body mistakenly identifies some of its cells and tissues as foreign. The immune system, which usually helps to fight off harmful, foreign substances such as bacteria or viruses, begins to attack healthy cells and tissues. The result is inflammation marked by redness, heat, pain and swelling. Doctors do not know why the immune system is awry in children who develop JRA.
Scientists suspect that it is a two-step process. First, something in a child’s genetic makeup gives them a tendency to develop JRA, and then an environmental factor, such as a virus, triggers the development of JRA.
The most common symptoms of all types of JRA are persistent joint swelling, pain, and stiffness that are typically worse in the morning or after a nap. The pain may limit movement of the affected joint, although many children, especially younger ones, will not complain of pain. JRA commonly affects the knees and joints in the hands and feet. One of the earliest signs of JRA may be limping in the morning because of an affected knee. Besides joint symptoms, children with systemic JRA have a high fever and a light pink rash. The rash and fever may appear and disappear very quickly. Systemic JRA also may cause lymph nodes in the neck and other body parts to swell.
In some cases (less than half), internal organs, including the heart and, very rarely, the lungs, may be involved. Eye inflammation is a potentially severe complication that sometimes occurs in children with pauciarticular IRA. Eye diseases such as iritis and uveitis often are not present until a child first develops JRA. There are typically periods when the symptoms of JRA are better or disappear (remissions) and times when symptoms are worse (flares). JRA is different in each child-some may have just one or two bursts and never have symptoms again, while others experience many flares or even have symptoms that never go away.
The difference between JRA and Adult RA: The main difference between juvenile and adult rheumatoid arthritis is that many people with JRA outgrow the illness, while adults usually have lifelong symptoms. Studies estimate that JRA symptoms disappear in more than half of all affected children by adulthood. Additionally, unlike rheumatoid arthritis in an adult, JRA may affect bone development and the child’s growth. Another difference between JRA and adult rheumatoid arthritis is the percentage of positive people for RF. About 70 to 80 percent of all adults with rheumatoid arthritis are positive for RF, but fewer than half of all children with rheumatoid arthritis are RF positive. RF indicates an increased chance that JRA will continue into adulthood.