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Juvenile dermatomyositis is an inflammatory disease of the muscle (myositis), skin, and blood vessels that affects about three in one million children each year. The cause is unknown. Most patients with JDM experience muscle weakness and skin rash. All age and ethnic groups are affected. Most cases start during childhood at ages 5 -10 and adults may also develop it at around age 40 - 50. Girls are affected about twice as often as boys.
Patients with JMD develop weakness in the large muscles around the neck, shoulders, and hips. This causes difficulty in climbing stairs, getting into cars, getting up from a chair or off the floor, or brushing hair. Most patients have little, if any, pain in their muscles, which distinguishes them from patients with other forms of muscle disease. Many patients with other conditions complain of weakness; however, when questioned closely, they really mean that they are tired, short of breath, or depressed rather than suffering from true muscle weakness, as is seen in patients with JDM.
Dermatomyositis is in a group of diseases or disorders of the muscles called inflammatory myopathies. The cause of most inflammatory myopathies is unknown; however, the leading theory is that the body's immune system mistakenly directs inflammation against muscle cells and blood vessels in the skin and muscles causing damage, rash, and weakness.
The most common signs and symptoms of JDM include:
Other JDM signs and symptoms that may occur include:
There are a number of tests doctors may use to help diagnose juvenile dermatomyositis. These tests include:
The goal of treatments for juvenile dermatomyositis is to minimize inflammation, improve function, and prevent disability. The treatment should be early and requires a team approach between the rheumatologist, physical therapist, dermatologist, and primary care doctor. JDM is unique among most rheumatic diseases of childhood in that it can often be completely cured.
Corticosteroids alter the immune system, limiting the production of antibodies and reducing skin and muscle inflammation, as well as improving muscle strength and function. Corticosteroids, especially prednisone, are usually the first choice in treating inflammatory myopathies such as dermatomyositis, because they work quickly.
The doctor may start with a very high dose, often intravenously (administered directly into vein), and then decrease it as signs and symptoms improve. Signs of improvement may be seen in about two to four weeks as the inflammation is diminished, but full recovery will not be seen for months after initiating treatment. Often, physical therapy is required for strengthening and retraining the muscles that were damaged.
Standard treatment for JDM has been high-dose daily oral glucocorticoids (e.g., up to 2 mg/kg/day of prednisone, at times in divided doses), which is continued until clinical and laboratory improvements are evident and then reduced slowly over a two-year period (at least). Intravenous glucocorticoids (methylprednisolone) are also often used at the beginning of therapy. Most patients develop treatment-related side effects with the use of steroids. In many cases, however, prednisone is introduced early as a treatment option and may be discontinued before the two-year period is completed.
Prolonged use of corticosteroids can have serious and wide-ranging side effects, like weight gain, osteoporosis, and cataracts, so the doctor may recommend supplements like calcium and vitamin D to strengthen bone and regular eye exams to detect cataracts.
Other medications work slower, but have fewer side effects than corticosteroids like prednisone, and allow the patient to wean off steroids sooner (“spare” the steroids).
Other aspects of treating juvenile dermatomyositis include:
Other conditions associated with JDM include diabetes, celiac disease, and arthritis. While many patients with JDM can be cured, some develop a chronic disease; as such, it is important for patients to have good general health practices. These include eating a well-balanced, nutritious diet, maintaining a healthy, weight and managing any other chronic illnesses. Regular exercise is important to regain and maintain strength. It is important for employers, teachers, and family members to understand the limitations imposed by muscle weakness, particularly since patients may look entirely normal.
Reference: Myositis and You. Ed. Lisa Rider, MD, Lauren Pachman, MD, Frederick Miller, MD, Harriet Bollar, The Myositis Association, 2007.
Updated March 2019 by Johnathan Hausmann, MD, and reviewed by the American College of Rheumatology Committee on Communications and Marketing.
This information is provided for general education only. Individuals should consult a qualified health care provider for professional medical advice, diagnosis and treatment of a medical or health condition.