Diagnosing Systemic Juvenile Idiopathic Arthritis

Diagnosing Systemic Juvenile Idiopathic Arthritis
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Learn how doctors assess the early symptoms of systemic juvenile idiopathic arthritis (SJIA), a childhood rheumatic disease.

Early diagnosis and treatment are crucial for kids with SJIA. The longer SJIA is active, the greater the chance of joint damage and potentially serious complications. Yet diagnosis can be challenging. While the pediatrician will likely assess early signs of SJIA, a referral to a pediatric rheumatologist will help to ensure a prompt SJIA diagnosis.

SJIA Diagnostic Challenges

One challenge in diagnosing SJIA is that a key symptom—arthritis—often doesn’t show up at first. As a result, parents, and even pediatricians, might not think “arthritis” when they see recurrent fevers and rash. Yet according to the SJIA diagnostic criteria developed by the International League of Associations for Rheumatology (ILAR), a diagnosis of SJIA requires a high fever for at least two weeks and arthritis (joint pain and inflammation) in one or more joints for at least six weeks. Fortunately, pediatric rheumatologists are skilled at identifying SJIA and handling the sometimes conflicting challenges of diagnosing the disease.

There are no specific tests for SJIA, so doctors rely on their experience and expertise as well as the child’s medical history and a comprehensive physical exam to identify the disease. Laboratory and other tests can help confirm an SJIA diagnosis and rule out conditions that cause similar symptoms.

Health History

Doctors take a medical history to learn about past illnesses and current medications as well as details of current symptoms such as how long a child has had them. Knowing the length of time SJIA symptoms have been present helps rule out infections and other problems that can affect the joints temporarily.

Some parents find it helpful to keep a record of when fevers and other symptoms start; some even take photographs of the rash, which can come and go in a matter of hours. Documenting potential SJIA symptoms will help doctors make a timely diagnosis.

Physical Exam

Children who have a persistent fever and rash should have a thorough musculoskeletal exam, even if they don’t have obvious joint symptoms. During the physical exam, doctors look for tenderness, warmth, swelling, and reduced range of motion, especially in the knees, wrists, ankles, and hip joints—the ones most often affected by SJIA—as well as in the jaw and neck. 

In some children, joint inflammation affects the growth centers in bones, causing them to be shorter than normal and possibly uneven from one side to another, so doctors assess limb length and overall growth. “Since inflammation can affect skeletal growth, asymmetry in limb length, especially in the legs, can be an important clue to the presence of arthritis,” explains Peter Nigrovic, MD, director of the Center for Adults with Pediatric Rheumatic Illness (CAPRI) at Brigham and Women’s Hospital in Boston. Doctors also look for systemic signs of SJIA, including swollen lymph nodes and an enlarged liver or spleen.

Imaging Tests

X-rays are rarely helpful in diagnosing juvenile arthritis, but magnetic resonance imaging and, occasionally, an ultrasound may be used to detect early joint inflammation or to look for complications. A chest X-ray can reveal lung inflammation, and an ultrasound of the heart can show inflamed tissue in and around the heart.

Laboratory Findings

Although SJIA can’t be diagnosed with blood tests, certain laboratory findings can help support or disprove the diagnosis. It’s common for kids with SJIA to have the following:  

  • Extremely high white blood cell and platelet counts

  • Severe anemia due to poor iron absorption

  • Extremely high levels of ferritin, an iron-storing protein

  • Elevated inflammation markers, including erythrocyte sedimentation rate and C-reactive protein

  • No sign of antinuclear antibodies or rheumatoid factor antibodiesboth of which are often seen in the polyarticular form of juvenile idiopathic arthritis and other rheumatic diseases but rarely in SJIA

Similar Symptoms, Different Conditions

The term “differential diagnosis” is used to describe the process of differentiating between conditions with similar signs and symptoms. Many illnesses can cause fever, rash, and swollen joints, and they must be ruled out before diagnosing SJIA. Some of the most common misdiagnoses include the following:   

  • Viral or bacterial infections, including sepsis, a serious infection in the bloodstream

  • Some types of cancer, such as lymphoma, which starts in cells that are part of the immune system

  • Other rheumatic and autoinflammatory diseases such as systemic lupus erythematosus (SLE), juvenile dermatomyositis, and neonatal onset multisystem inflammatory disease, which cause inflammation of the nervous system, skin, and joints

  • Lyme disease, a bacterial infection that causes muscle and joint pain as it spreads

  • Inflammatory bowel disease, an autoinflammatory disease that primarily affects the digestive system

  • Kawasaki disease, a condition that causes inflammation in the arteries

Doctors sometimes take biopsies—small pieces of tissue—from the skin, lymph nodes, or bone marrow to rule out other diseases.

Despite the information from tests that help to detect SJIA or rule out other diseases, the medical history and physical exam remain the cornerstones of diagnosis. Thomas J.A. Lehman, MD, chief of pediatric rheumatology at Hospital for Special Surgery in New York City, explains that “[doctors] have to take the time to let the family tell [them] what’s happening, ask detailed questions and do a thorough examination of the child.”


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