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What Is Juvenile Rheumatoid Arthritis?
Juvenile rheumatoid arthritis is arthritis that causes joint inflammation and stiffness for more than 6 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. One type of JRA can also affect the internal organs. Doctors classify JRA into three types by the number of joints involved, the symptoms, and the presence or absence of certain antibodies found by a blood test. (Antibodies are special proteins made by the immune system.) These classifications help the doctor determine how the disease will progress and whether the internal organs or skin is affected.
- Pauciarticular (PAW-see-are-TICK-you-lar)--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. Pauciarticular disease typically affects large joints, such as the knees. Girls under age 8 are most likely to develop this type of JRA.
Some children have special kinds of antibodies in the blood. One is called antinuclear antibody (ANA) and one is called rheumatoid factor. Eye disease affects about 20 to 30 percent of children with pauciarticular JRA. Up to 80 percent of those with eye disease also test positive for ANA and the disease tends to develop at a particularly 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, the colored part of the eye) or uveitis (inflammation of the uvea, or the inner eye). Some children with pauciarticular disease outgrow arthritis by adulthood, although eye problems can continue and joint symptoms may recur in some people.
- Polyarticular--About 30 percent 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 disease 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 antibody in their blood called IgM rheumatoid factor (RF). These children often have a more severe form of the disease, which doctors consider to be similar in many ways to adult rheumatoid arthritis.
- Systemic--Besides joint swelling, the systemic form of JRA is characterized by fever and a light skin rash, and may also affect internal organs such as the heart, liver, spleen, and lymph nodes. Doctors sometimes call it Still's disease. Almost all children with this type of JRA test negative for both RF and ANA. The systemic form affects 20 percent 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.
What Causes Juvenile Rheumatoid Arthritis?
JRA is an autoimmune disorder, which means that the body mistakenly identifies some of its own cells and tissues as foreign. The immune system, which normally 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 goes 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; then an environmental factor, such as a virus, triggers the development of JRA.
What Are the Symptoms and Signs of Juvenile Rheumatoid Arthritis?
The most common symptom of all types of JRA is persistent joint swelling, pain, and stiffness that typically is 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 skin rash. The rash and fever may appear and disappear very quickly. Systemic JRA also may cause the lymph nodes located in the neck and other parts of the body 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 JRA. Eye diseases such as iritis and uveitis often are not present until some time after a child first develops JRA.
Typically, there are periods when the symptoms of JRA are better or disappear (remissions) and times when symptoms are worse (flare-ups). JRA is different in each child--some may have just one or two flare-ups and never have symptoms again, while others experience many flare-ups or even have symptoms that never go away.
Some children with JRA may have growth problems. Depending on the severity of the disease and the joints involved, growth in affected joints may be too fast or too slow, causing one leg or arm to be longer than the other. Overall growth may also be slowed. Doctors are exploring the use of growth hormones to treat this problem. JRA also may cause joints to grow unevenly or to one side.
How Is Juvenile Rheumatoid Arthritis Diagnosed?
Doctors usually suspect JRA, along with several other possible conditions, when they see children with persistent joint pain or swelling, unexplained skin rashes and fever, or swelling of lymph nodes or inflammation of internal organs. A diagnosis of JRA also is considered in children with an unexplained limp or excessive clumsiness.
No one test can be used to diagnose JRA. A doctor diagnoses JRA by carefully examining the patient and considering the patient's medical history, the results of laboratory tests, and x rays that help rule out other conditions.
- Symptoms --One important consideration in diagnosing JRA is the length of time that symptoms have been present. Joint swelling or pain must last for at least 6 weeks for the doctor to consider a diagnosis of JRA. Because this factor is so important, it may be useful to keep a record of the symptoms, when they first appeared, and when they are worse or better.
- Laboratory tests--Laboratory tests, usually blood tests, cannot by themselves provide the doctor with a clear diagnosis. But these tests can be used to help rule out other conditions and to help classify the type of JRA that a patient has. Blood may be taken to test for RF and ANA, and to determine the erythrocyte sedimentation rate (ESR).
- ANA is found in the blood more often than RF, and both are found in only a small portion of JRA patients. The RF test helps the doctor tell the difference among the three types of JRA.
- ESR is a test that measures how quickly red blood cells fall to the bottom of a test tube. Some people with rheumatic disease have an elevated ESR or "sed rate" (cells fall quickly to the bottom of the test tube), showing that there is inflammation in the body. Not all children with active joint inflammation have an elevated ESR.
- X rays--X rays are needed if the doctor suspects injury to the bone or unusual bone development. Early in the disease, some x rays can show cartilage damage. In general, x rays are more useful later in the disease, when bones may be affected.
- Other diseases--Because there are many causes of joint pain and swelling, the doctor must rule out other conditions before diagnosing JRA. These include physical injury, bacterial or viral infection, Lyme disease, inflammatory bowel disease, lupus, dermatomyositis, and some forms of cancer. The doctor may use additional laboratory tests to help rule out these and other possible conditions. ·
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