Juvenile Rheumatoid Arthritis: Diagnostic Steps

National Institute of Arthritis and Musculoskeletal and Skin Diseases

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 and the results of laboratory tests that help rule out other conditions.

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 pink 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 (flares). JRA is different in each child-some may have just one or two flares and never have symptoms again, while others experience many flares or even have symptoms that never go away.

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 or 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 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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