Juvenile dermatomyositis is one of the conditions in a group of conditions called the dermatomyositis/polymyositis complex. The conditions in this complex are characterized by muscle damage due to an inflammatory process of the blood vessels that lie under the skin and muscles. Skin changes around the eyelids and over the knuckles and finger joints are also seen. Juvenile dermatomyositis is the condition most often seen in children.
Juvenile dermatomyositis is rare, affecting 3,000 to 5,000 U.S. children under the age of 18.
The cause of juvenile dermatomyositis has not yet been determined. However, factors which are thought to be associated with dermatomyositis include dysfunction of the immune system, resulting in infections.
The symptoms of juvenile dermatomyositis often appear gradually. At times, there may be a more acute, or intense, onset of symptoms. The following are the most common symptoms of juvenile dermatomyositis. However, each child may experience symptoms differently. Symptoms may include:
Rash around the eyelids and/or knuckles and finger joints; a rash may also occur on the elbows, knees, and ankles
Muscle pain and tenderness
Weight loss (due to difficulty swallowing)
Joint pain and inflammation
Calcium deposits under the skin (calcinosis)
Symptoms of juvenile dermatomyositis may resemble other medical conditions or problems. Always consult your child's doctor for a diagnosis.
The course of juvenile dermatomyositis is often divided into four phases based on symptoms and findings on examination. The four phases are briefly described below:
Prodromal period. This phase can last for weeks or months. The symptoms seen during this period are nonspecific (general symptoms that can indicate many different conditions).
Progressive muscle weakness and rash. In this phase, muscle weakness increases for days and weeks and then stabilizes. Once the stabilization occurs, it may last from one to two years before recovery.
Persistent muscle weakness, muscle inflammation, and rash. During this phase, symptoms include persistent muscle weakness, active inflammation of the muscles, and rash lasting up to two years.
Recovery. Recovery may occur without any apparent consequences, or may occur after two or more years with residual muscle weakness, atrophy (wasting), or contractures (a condition in which muscles in a particular location may become permanently paralyzed as a result of lack of use).
In addition to a complete medical history and physical examination, diagnostic procedures for juvenile dermatomyositis may include:
Laboratory tests. These tests are used to assess the presence of antibodies, muscle enzymes, and indicators of inflammation in the blood.
Electromyography (EMG). An electrical test to determine nerve or muscle damage.
Muscle biopsy. Removal of a small piece of muscle for microscopic examination.
X-rays. A diagnostic test that uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.
Magnetic resonance imaging (MRI). A diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.
Juvenile dermatomyositis cannot be cured. However, with supportive therapy and a multidisciplinary team approach to treatment, remission of the disease may be achievable in time. Treatment may include:
Medications. Medications, such as glucocorticosteroids and methotrexate, are used to treat the inflammatory process, and hydroxychloroquine is used to help treat the skin disease of dermatomyositis.
Physical and occupational therapy. This can help to improve muscle function and strength.
Liberal use of sunscreen. Sunscreen helps to prevent further irritation or damage to the skin.
Nutritional support. This can help to ensure an adequate diet.