Juvenile Dermatomyositis (JD)
Juvenile dermatomyositis (JDM) is an inflammatory disease that causes muscle weakness and a skin rash on the eyelids and knuckles. It affects an estimated 3,000-5,000 children in the United States. All age and ethnic groups are affected. Most cases occur in children ages 5-10. Roughly 1 in 5 children also has joint symptoms, but they are likely to be mild. Remission is possible, but a minority of children with JDM may have a more chronic disease course.
The cause of juvenile dermatomyositis is unknown. It is believed that abnormalities in the body's immune system lead to inflammation and damage to muscle cells or the blood vessels in the muscle and skin.
The first sign of JDM is usually a red or purplish skin rash on the eyelids or cheeks. A patchy rash may also appear around the nails, elbows, knees, chest and back. Muscle weakness may begin at the same time as the skin rash, or it may begin days, weeks or months after. The weakness is usually in the neck, shoulders, back and stomach. Running, climbing stairs, sitting from a lying position or standing from a seated position may become difficult.
Other signs may include falling, weak voice (dysphonia) or problems swallowing (dysphagia). About half of children with JDM have pain in their muscles. Some children may develop calcinosis (hardened lumps of calcium under the skin) or contractures, in which muscles shorten and cause joints to stay bent.
To make a diagnosis of JDM, the doctor will examine the child and ask questions about his or her medical history and symptoms. The telltale dermatomyositis rash is an important part of the diagnosis. Specific diagnostic tests that may be done include:
- Magnetic resonance imaging. MRI can reveal subtle muscle inflammation and swelling early in the disease.
- Electromyography. This test measures the electrical activity in the muscles by inserting a thin needle into the affected area.
- Muscle biopsy. A small piece of muscle tissue is removed and examined under a microscope. In JDM, inflammatory cells surround and damage the small blood vessels in the muscle. This can be seen with a biopsy.
- Blood tests. Laboratory tests can measure the levels of certain enzymes (proteins) produced by inflamed muscles. A blood test also can detect autoantibodies associated with JDM, which can help determine the best treatment.
- Nailfold capillaroscopy. This noninvasive test involves placing a bit of oil onto the skin at the bottom of a fingernail. The nail is then examined using a magnifying scope. It can reveal swelling and changes in the capillaries (blood vessels).
The goal of JDM treatment is to reduce inflammation, improve function and prevent disability. This is accomplished through a combination of medications, physical and speech therapy and self-care methods.
Medications that may be prescribed include:
- Corticosteroids. Corticosteroids are powerful anti-inflammatory drugs. They often are used first in treating inflammatory myopathies such as JDM, because they work quickly. Due to side effects, they are not used for a long time.
- Methotrexate. Methotrexate works more slowly to reduce inflammation in JDM, but it has fewer side effects than corticosteroids.
- Intravenous immunoglobulin (IVIg). Immunoglobulin contains healthy antibodies from blood donors. They can block harmful antibodies that attack muscle and skin.
- Other drugs. Other medications that may be used in the treatment of JDM include cyclosporine, azathioprine, tacrolimus, hydroxychloroquine or anti-TNF therapy.
Additional treatments include:
- Physical therapy. Exercises can maintain and improve strength and flexibility. Physical therapy is directed at preventing muscle wasting, stiffness and contractures.
- Speech therapy. If the throat muscles become weak, speech therapy can help improve speech and swallowing.
- Skin protection. Sun protection may help control skin disease and potential muscle disease. Sunscreen, wide-brimmed hats, protective clothing and avoiding sun exposure during peak hours are important.
Since JDM can be a chronic (long-term) disease, it is important to take a proactive part in treatment. Maintaining good general health is essential. Physical activity and performing prescribed physical therapy exercises will help the person regain and maintain muscle strength. If swallowing is affected, preparing foods that are safe to eat and performing speech therapy exercises will aid in nutrition and overall well-being.