Dermatomyositis

Definition

Dermatomyositis is one of a group of relatively uncommon diseases known as inflammatory myopathies , or inflammatory disorders of the muscles. Dermatomyositis is distinguished from other diseases in this category by the fact that it causes a characteristic skin rash as well as affecting the strength and functioning of the muscles. Dermatomyositis in children and adolescents is called juvenile dermatomyositis (abbreviated JDMS or simply JD) because it is different from the adult form of the disorder in several respects. The most significant differences between JDMS and adult dermatomyositis are as follows:

• Children are more likely than adults to develop calcinosis (calcium deposits in the skin) and gastrointestinal symptoms.
• Children are more likely to develop pains in the joints.
• Adults with dermatomyositis over the age of 50 have a 15 percent risk of developing cancer , whereas juvenile dermatomyositis is rarely associated with malignancy.

Description

JDMS is sometimes called childhood idiopathic dermatomyositis. The word idiopathic means that the cause of the disease is unknown and that it appears to begin spontaneously. The disorder is also occasionally defined as a systemic vasculopathy, systemic meaning that it affects the body as a whole rather than just one part, and vasculopathy meaning that it affects the blood vessels.

JDMS usually begins with a reddish or reddish-purple rash, called a heliotrope rash because of its color. In most children the rash first appears on the eyelids or cheekbone area and is often mistaken for an allergy symptom. It may also appear as dry patches of reddened skin on the child's knuckles, knees, elbows, or ankles that are often misdiagnosed as eczema. In a few children, the rash may spread over the entire body. In some children, the rash is made worse by exposure to sunlight.

The heliotrope rash is either accompanied or followed by weakness of the body's central muscles; that is, the muscles on or close to the trunk of the body. These muscles are also called proximal muscles. The child may complain of tiredness and have trouble sitting up, standing, or moving the neck, shoulders, abdomen, back, or hips. The muscular weakness varies in severity; while some children may simply have less energy than usual, others may be literally unable to get out of bed or may have trouble swallowing or breathing. In some cases the child's voice may sound as if he or she is talking through the nose.

The third major symptom of juvenile dermatomyositis is a low-grade fever (one or two degrees Fahrenheit above normal).

Transmission

Although fever is one of the most common symptoms of JDMS, the disease cannot be transmitted from one child to another.

Demographics

Juvenile dermatomyositis most commonly affects children between the ages of five and 15 years of age. The ratio of girls to boys is 2:1. The disease is thought to be equally common around the world, affecting about three children per million. It is estimated that 3,000 to 5,000 children in the United States have JDMS as of the early 2000s. The incidence appears to be increasing, however. Although Caucasian children are affected more often than African-American children, the rate is rising faster among African Americans. The reasons for this increase are not known as of 2004.

JDMS has a seasonal pattern in North America, occurring more frequently in the spring and summer months.

Causes and symptoms

Causes

The precise causes of JDMS are not yet fully understood. One theory holds that the disease is an autoimmune reaction caused by the body's abnormal response to a virus. In an autoimmune reaction, the body begins to attack its own tissues after it has successfully eliminated the virus. Some researchers have identified virus-like structures in the muscle cells of patients known to have dermatomyositis, while others have noted that children newly diagnosed with JDMS often have a history of infection with a Coxsackie virus within three months of the first JDMS symptoms.

Genetic factors are also thought to be involved in juvenile dermatomyositis. In 2002 a group of researchers at Northwestern University reported that susceptibility to JDMS is related to a genetic marker known as DQA1*0501. Another team of doctors at the Children's National Medical Center in Washington, DC, has suggested that children with this particular genetic marker develop JDMS when a viral infection triggers an abnormal interaction among the body's immune system, the muscles, and the vascular system. There may also be other genes that increase children's susceptibility to the disease that have not yet been identified.

Symptoms

The major symptoms of juvenile dermatomyositis include a characteristic reddish or purplish rash called a heliotrope rash; weakness or pain in the proximal muscles; and a low-grade fever.

Other symptoms that may occur in children with juvenile dermatomyositis include:

• Contractures: A contracture is an abnormal shortening of the muscles near a joint that causes the joint to remain in a bent position. JDMS may lead to contractures for two reasons. The first is that the muscle may form scar tissue during the healing process. The second is that the child may avoid exercising his or her muscles because he or she feels weak. The muscles then gradually lose their ability to hold the joint in its proper position.
• Stunted or slowed growth: The child may grow more slowly than normal during an acute attack of JDMS because some of the medications used to treat the disease slow down the growth of bones. In addition, some of the body's energy that is ordinarily used for growth is used instead to fight off the disease.
• Sore or swollen joints: About half of all children diagnosed with JDMS have sore or swollen joints, caused by the inflammation of the muscles around the joints. The joint may feel warm to the touch and look reddish as well as swollen.
• Vasculitic ulcers: Vasculitis refers to inflammation of a blood vessel. A vasculitic ulcer is a hole or tear that develops in the tissues around an inflamed blood vessel. In children with JDMS, vasculitic ulcers usually appear either in the skin rash or in the digestive tract. Vasculitic ulcers in the skin look like open sores within the reddish-purple rash; they vary in size from small spots to sores as much as an inch across. Vasculitic ulcers in the digestive tract may lead to perforation of the intestines, which is a medical emergency.
• Calcinosis: Calcinosis is a condition in which small lumps of calcium compounds develop beneath the skin or in the muscles of children with JDMS. They affect between 50 percent and 60 percent of children with the disorder and range in size from less than a millimeter across to lumps the size of small pebbles. Large lumps may interfere with the movement of the muscles, cause pain if they are located close to a joint, or even break through the skin. In most cases, however, the pieces of calcium are reabsorbed by the body during the recovery process.
• Dysphagia: Dysphagia refers to difficulty or discomfort when swallowing. Children whose throat muscles are affected by the disorder may experience difficulty in swallowing food; some lose weight because the dysphagia affects their appetite.
• Abnormal heart rhythms and myocarditis: Myocarditis refers to inflammation of the muscles of the walls of the heart. About 50 percent of children with JDMS develop an abnormal heart rhythm.

When to call the doctor

It is not always easy to tell when a child might have juvenile dermatomyositis. The skin rash associated with JDMS is often mistaken for eczema. In addition, some children may develop a mild form of muscle weakness before the telltale rash appears. While about 50 percent of children diagnosed with JDMS have an acute onset of symptoms, the other 50 percent have what is called a subacute onset, which means that the symptoms are milder and come on more slowly. While most children with acute symptoms are diagnosed within three months, the correct diagnosis of children with subacute symptoms may take a year or even longer.

Children who have developed sudden weakness of the muscles that control breathing or swallowing, or those who have developed vasculitic ulcers in the digestive tract may need to be hospitalized. Parents should call the doctor at once if they notice any of the following symptoms:

• choking on food or being unable to swallow
• weak voice or total loss of voice
• severe pain in the abdomen
• coal-black or tarry-looking stools
• change in bowel habits
• passing red blood with stools

Diagnosis

History and physical examination

The first step in diagnosing juvenile dermatomyositis is the taking of a complete history and giving the child a thorough physical examination. The doctor will ask the child and the parents when the symptoms began, what parts of the body are affected, whether the child can keep up his or her normal activities, and (in some cases) whether other family members have arthritis or muscle diseases.

During the physical examination, the doctor looks for several specific signs and symptoms, including heliotrope rash on the child's face, knuckles, knees, elbows, or the cuticles of the fingers; swelling around the eyes; a nasal quality to the child's voice; sore or weak muscles; and sore or swollen joints. The doctor will test the strength of the muscles by asking the child to lift his or her head, arms, or legs while the doctor gently pushes or presses downward.

The child's doctor may use a set of criteria first established in 1975 as part of the process of diagnosis. These so-called Bohan-Peter criteria are interpreted as follows: If the child meets the first criterion (the characteristic rash), three of the remaining four criteria must be met to make the diagnosis of juvenile dermatomyositis. The last three criteria listed below require special laboratory tests. If two out of four are met, the child is considered to have "probable" JDMS:

• heliotrope rash
• weakness of the central muscles on both sides of the body
• a higher than normal level of muscle enzymes in the blood
• a specific pattern of changes in the muscle tissue caused by inflammation
• an abnormal pattern of electrical activity in the muscles

Laboratory tests

The doctor will have a sample of the child's blood tested for certain muscle enzymes known as aldolase and CPK. These enzymes are leaked into the blood stream when muscles become inflamed. Abnormally high levels of aldolase and CPK indicate muscle damage. In addition to testing for muscle enzymes, the doctor may also have the blood sample tested for antinuclear antibodies (ANA), which are produced when a person's immune system is producing antibodies against the body's own tissues. Between 60 percent and 80 percent of children with JDMS have elevated levels of ANA.

A muscle biopsy may also be performed. In this test, the doctor removes a small piece of muscle tissue and has it examined under a microscope to see whether the muscle fibers and nearby blood vessels have undergone certain changes that indicate JDMS. Many doctors, however, skip this test if the child has the typical heliotrope rash, shows signs of muscle weakness during the physical examination, and has high muscle enzyme levels in the blood test. A muscle biopsy is necessary, however, if the child has the heliotrope rash but normal enzyme levels.

An electromyogram (EMG) measures electrical activity in the muscles. The doctor pierces the child's skin with a thin needle connected to a wire running to a machine that records the pattern of electrical activity in the muscle tissue. EMGs are not always performed, however, because the test is somewhat painful.

Imaging studies

Some doctors may order a magnetic resonance imaging (MRI) test in order to evaluate the presence of inflammation in the muscles of children with normal muscle enzyme levels in their blood. It may also be done in order to identify appropriate muscles for testing when a biopsy is necessary.

Treatment

The treatment of juvenile dermatomyositis involves a combination of approaches. The treatment plan may also have to be changed periodically as the child's symptoms change.

Medications

Medications are the mainstay of treatment for juvenile dermatomyositis. The most common drug used is prednisone, a steroid that is given to reduce pain, control the fever and skin rash, and improve the strength of the child's muscles. Prednisone may be given in pill form or as a weekly intravenous infusion. Unfortunately, prednisone has a number of side effects, ranging from high blood pressure, weight gain, and stretch marks to mood changes and weak or damaged bones. If taken for a long period of time, prednisone may also lead to the development of eye cataracts and slow down the child's growth.

Another drug that is used to treat JDMS is methotrexate, an immunosuppressive drug that may be taken as pills or given as an injection. Methotrexate works by slowing down the immune system. It is usually given together with prednisone. It also has some potentially serious side effects, including nausea and vomiting , diarrhea , increased susceptibility to infections, skin rashes , a decrease in the number of blood cells, and potential liver damage. In some cases, the doctor may recommend another immunosuppressive drug known as cyclosporine to be taken together with methotrexate. If the child's skin rash is unusually severe, the doctor may prescribe hydroxychlorethotrexate (Plaquenil). Methotrexate, cyclosporine, and hydroxychlorethotrexate all belong to a category of medications known as disease-modifying anti-rheumatic drugs, or DMARDs.

Exercise and physical therapy

Exercise and physical therapy are an important part of treatment for JDMS because they help to prevent contractures, keep the child's joints flexible, and strengthen muscles. In most cases, the child will be referred to a physical therapist who can design an exercise program for the specific sets of muscles affected by the disease. The exercise program is modified as the child's strength gradually returns.

Psychotherapy

Because JDMS usually requires two years or even longer of drug treatments, exercise programs, limitations on some activities, and special attention to diet, children often become angry, depressed, or self-pitying. In some cases they may express resentment toward healthy siblings or classmates. The child's doctor may recommend either individual psychotherapy for the affected child or family therapy for the family as a whole.

Alternative treatment

Very little has been published regarding complementary and alternative (CAM) treatments for juvenile dermatomyositis, although some practitioners of traditional Chinese medicine (TCM) have reported success in treating the fever and heliotrope rash of JDMS with various Chinese herbal formulae.

Nutritional concerns

Children diagnosed with JDMS must eat a regular balanced diet with generous amounts of protein and calcium. The protein is necessary to repair damaged muscle tissue, and the calcium is needed to keep the child's bones strong. Because of the possible side effects of prednisone, however, the diet must be low in salt and sugar. More specifically, the child should not be allowed to eat take-out or fast foods except on rare occasions as a special treat. Parents should consult a professional dietitian or nutritionist to help plan a diet that is appealing to the child as well as healthful.

Prognosis

The prognosis of juvenile dermatomyositis varies but is usually related to the child's age and the severity of the vasculitis associated with the disease. Younger children generally recover more rapidly than adolescents. Most children with JDMS have active symptoms for about two years, although some may be able to do without medications after the first year and others may need drug treatment and physical therapy for many years. Some children recover without any relapses; however, most children with the disease have periods of remission alternating with recurrences of the symptoms.

Most children eventually recover completely from juvenile dermatomyositis; however, some have lifelong stiffness or muscle weakness from the disease. In a very few cases the child may die from complications related to myocarditis or from bowel perforation or lung disease caused by vasculitic ulcers.

Prevention

Because the causes are still unknown, there is no way to prevent juvenile dermatomyositis as of 2004.

Parental concerns

Although JDMS is rarely fatal, it can lead to medical emergencies if the child develops vasculitic ulcers. More commonly, however, the disease has a severe impact on families because of the length and complexity of treatment as well as the possibility of complications from the disease itself and side effects from the medications. Although two years is the average length of acute symptoms, some children are affected for years, even into adulthood. In addition, the unpredictable nature of remissions and recurrences can be difficult to handle. If the child with JDMS has siblings, the parents must balance the needs of the affected child with the needs of healthy siblings. It is not unusual for either the affected child or other children in the family to develop emotional or behavioral problems. The Myositis Association and the Muscular Dystrophy Association, which are listed below under Resources, can help parents find support groups in their area for dealing with family members' emotional reactions to the disease as well as other problems of daily living.

With regard to education, most children with JDMS can continue to attend their regular school although they may need special transportation. They should not be isolated from other children.

See also Juvenile arthritis ; Myopathies ; Vasculitides .

Resources

BOOKS

Parker, James, et al. The Official Patient's Sourcebook on Dermatomyositis. San Diego, CA: Icon Group International, 2002.

"Polymyositis and Dermatomyositis." Section 5, Chapter 50 in The Merck Manual of Diagnosis and Therapy , edited by Mark H. Beers and Robert Berkow. Whitehouse Station, NJ: Merck Research Laboratories, 2002.

PERIODICALS

Chari, Geetha, and Teresita A. Laude. "Juvenile Dermatomyositis: An Overview." International Pediatrics 15 (January 2000): 21–5.

Duffy, C. M. "Health Outcomes in Pediatric Rheumatic Disease." Current Opinion in Rheumatology 16 (March 2004): 102–8.

Koler, Anthony, and Andrew Montemarano. "Dermatomyositis." American Family Physician 64 (November 1, 2001): 1565–72.

Pachman, L. M. "Juvenile Dermatomyositis: Immunogenetics, Pathophysiology, and Disease Expression." Rheumatic Diseases Clinics of North America 28 (August 2002): 579–602.

Rao, Y. A. "Survey on TCM Treatment of Polymyositis and Dermatomyositis." Journal of Traditional Chinese Medicine 23 (September 2003): 230–35.

Tezak, Z., et al. "Gene Expression Profiling in DQA1*0501+ Children with Untreated Dermatomyositis: A Novel Model of Pathenogenesis." Journal of Immunology 168 (April 15, 2002): 4154–63.

Wedderburn, L. R., and C. K. Li. "Paediatric Idiopathic Inflammatory Muscle Diseases." Best Practice and Research: Clinical Rheumatology 18 (June 2004): 345–58.

Zipitis, C. S., et al. "Treatment Approaches to Juvenile Dermatomyositis." Expert Opinion on Pharmacotherapy 5 (July 2004): 1509–15.

ORGANIZATIONS

American Academy of Dermatology (AAD). PO Box 4014, Schaumburg, IL 60168–4014. Web site: http://www.aad.org.

Arthritis Foundation. PO Box 7669, Atlanta, GA 30357–0669. Web site: http://www.arthritis.org.

Muscular Dystrophy Association (MDA). 3300 East Sunrise Drive, Tucson, AZ 85718–3208. Web site: http://www.mdausa.org.

Myositis Association. 1233 20th Street NW, Suite 402, Washington, DC 20036. Web site: http://www.myositis.org.

National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). 1 AMS Circle, Bethesda, MD 20892–3675. Web site: http://www.niams.nih.gov.

National Institute of Neurological Disorders and Stroke (NINDS). National Institutes of Health. 9000 Rockville Pike, Bethesda, MD 20892. Web site: http://www.ninds.nih.gov.

WEB SITES

Callen, Jeffrey P. "Dermatomyositis." eMedicine , December 5, 2002. Available online at http://www.emedicine.com/derm/topic98.htm (accessed November 24, 2004).

"Juvenile Dermatomyositis (JDMS)." Arthritis Foundation. Available online at http://www.arthritis.org/conditions/DiseaseCenter/jdms.asp (accessed November 24, 2004).

Mayo Clinic Staff. "Dermatomyositis." MayoClinic.com , October 15, 2003. Available online at http://www.mayoclinic.com/invoke.cfm?id=DS00335 (accessed November 24, 2004).

OTHER

National Institute of Neurological Disorders and Stroke (NINDS). NINDS Dermatomyositis Information Page . Bethesda, MD: NINDS, 2003.

Rebecca Frey, PhD