Juvenile dermatomyositis (JDM) is an inflammatory disorder that affects the skin and muscles. All age groups can be affected, but it is most common between the ages of five and 14 years old. Girls are more commonly affected than boys. JDM is part of a group of diseases called idiopathic inflammatory myopathies, which are characterized by inflammation of the vessels of the skin and the muscles, resulting in skin rash and muscle weakness. JDM can also involve other organ systems, including the gastrointestinal tract, heart, joints, kidneys, lungs or eyes.
The most characteristic findings of JDM are rashes and muscle weakness. The rash is typically near the eyelids and cheeks, and may look red or purplish. Red patches may also be visible over the knuckles. Usually, the muscles of the neck, thighs and upper arms are the most severely affected, which may cause children to have difficulty with climbing stairs, getting dressed or brushing their hair. Some children have trouble swallowing, or may develop a new, nasal quality to their voices. Symptoms of JDM may appear suddenly or gradually, and each child may experience different symptoms at different times. Other symptoms of JDM include fever, fatigue, joint pain, and weight loss. Some children, particularly those who have had disease for a long time, develop calcium deposits under the skin (calcinosis), which may feel like hard or painful lumps.
The diagnosis of JDM is made based on a combination of clinical history, a physical exam, laboratory testing and imaging. Useful laboratory tests include blood tests looking for evidence muscle inflammation. Magnetic resonance imaging (MRI) of the thighs is also a helpful way to view inflammation in the muscles. If the diagnosis is still unclear, your child’s physician may recommend a muscle biopsy.
There is no cure for juvenile dermatomyositis. However, there are effective treatments that can help reduce or eliminate the symptoms. Immunosuppression with medications such as glucocorticoids, methotrexate, IVIG or hydroxychloroquine are typically used to treat the inflammatory process. In some cases, stronger immunosuppressive medications may be used. Physical and occupational therapy are extremely important for improving and maintaining muscle strength. Sun protection is also encouraged, as UV exposure may lead to a disease flare.
Reviewed and edited by Sarah Faith Taber, MD