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Dermatomyositis

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.

KEY TERMS

Calcinosis A condition in which calcium salts are deposited in various body tissues. In juvenile dermatomyositis, calcinosis usually takes the form of small lumps of calcium compounds deposited in muscles or under the skin.

Contracture A tightening or shortening of muscles that prevents normal movement of the associated limb or other body part.

Coxsackie virus A type of enterovirus that may produce a variety of illnesses, including upper respiratory infections, myocarditis, and pericarditis. Coxsackieviruses resemble the virus that causes polio.

Cutaneous Pertaining to the skin.

Disease-modifying anti-rheumatic drugs (DMARDs) A group of medications given to treat severe cases of arthritis, JDMS, and other diseases that affect the joints. All DMARDs work by modifying the immune system.

Dysphagia Difficulty in swallowing.

Heliotrope A plant (Heliotropium arborescens ) related to borage that has lavender or deep violet flowers. The characteristic skin rash of JDMS is sometimes called a heliotrope rash because of its reddish-purple color.

Idiopathic Refers to a disease or condition of unknown origin.

Myocarditis Inflammation of the heart muscle (myocardium).

Myopathy Any abnormal condition or disese of muscle tissue, characterized by muscle weakness and wasting.

Myositis Inflammation of the muscle.

Proximal muscles The muscles closest to the center of the body.

Remission A disappearance of a disease and its symptoms. Complete remission means that all disease is gone. Partial remission means that the disease is significantly improved, but residual traces of the disease are still present. A remission may be due to treatment or may be spontaneous.

Rheumatologist A doctor who specializes in the diagnosis and treatment of disorders affecting the joints and connective tissues of the body.

Vasculopathy Any disease or disorder that affects the blood vessels.

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): 215.

Duffy, C. M. "Health Outcomes in Pediatric Rheumatic Disease." Current Opinion in Rheumatology 16 (March 2004): 1028.

Koler, Anthony, and Andrew Montemarano. "Dermatomyositis." American Family Physician 64 (November 1, 2001): 156572.

Pachman, L. M. "Juvenile Dermatomyositis: Immunogenetics, Pathophysiology, and Disease Expression." Rheumatic Diseases Clinics of North America 28 (August 2002): 579602.

Rao, Y. A. "Survey on TCM Treatment of Polymyositis and Dermatomyositis." Journal of Traditional Chinese Medicine 23 (September 2003): 23035.

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): 415463.

Wedderburn, L. R., and C. K. Li. "Paediatric Idiopathic Inflammatory Muscle Diseases." Best Practice and Research: Clinical Rheumatology 18 (June 2004): 34558.

Zipitis, C. S., et al. "Treatment Approaches to Juvenile Dermatomyositis." Expert Opinion on Pharmacotherapy 5 (July 2004): 150915.

ORGANIZATIONS

American Academy of Dermatology (AAD). PO Box 4014, Schaumburg, IL 601684014. Web site: <www.aad.org>.

Arthritis Foundation. PO Box 7669, Atlanta, GA 303570669. Web site: <www.arthritis.org>.

Muscular Dystrophy Association (MDA). 3300 East Sunrise Drive, Tucson, AZ 857183208. Web site: <www.mdausa.org>.

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

National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). 1 AMS Circle, Bethesda, MD 208923675. Web site: <www.niams.nih.gov>.

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

WEB SITES

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

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

Mayo Clinic Staff. "Dermatomyositis." MayoClinic.com, October 15, 2003. Available online at <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

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"Dermatomyositis." Gale Encyclopedia of Children's Health: Infancy through Adolescence. . Encyclopedia.com. 15 Dec. 2017 <http://www.encyclopedia.com>.

"Dermatomyositis." Gale Encyclopedia of Children's Health: Infancy through Adolescence. . Encyclopedia.com. (December 15, 2017). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/dermatomyositis-0

"Dermatomyositis." Gale Encyclopedia of Children's Health: Infancy through Adolescence. . Retrieved December 15, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/dermatomyositis-0

Dermatomyositis

Dermatomyositis

Definition

Dermatomyositis is one member of a group of diseases that are collectively called inflammatory myopathies. A myopathy is a disorder of a muscle. Hallmarks of dermatomyositis disease are a widespread rash and muscle weakness.

Description

Dermatomyositis is characterized by the onset of symptoms that can be severe, with rash and muscle weakness occurring over a large portion of the body. The term dermatomyositis stems from the root word "derm," referring to the skin, and the word "myositis," which means inflammation of muscles. Dermatomyositis, therefore, means an inflammation of the muscles and the skin. The disease was first described in 1887 in Germany.

Demographics

Both children and adults can be affected with dermatomyositis, but females are twice as likely to have the disorder as males. One-third of the cases occur in people over the age of 50. People of European ancestry have typically been more affected than people of African ancestry. As of 2004, however, the incidence of dermatomyositis is rising faster in African Americans than in whites. In the United States, the estimated prevalence of the disease is 5.5 cases per million people.

Causes and symptoms

The cause of dermatomyositis is a disruption in the functioning of the immune system, although the precise details of the malfunction are not yet known. While the basis of the disease may be due to a genetic mutation, conclusive evidence is lacking. Infection with certain viruses, or a bacterium called Borrelia (the cause of Lyme disease ), has been suggested as possible triggers of the disease.

Dermatomyositis is often first apparent as a rash. The rash, which can be bluish-purple in color, reminiscent of bruising, typically occurs in patches on the face, neck, shoulders, upper portion of the chest, elbows, knuckles, knees, and back. Sometimes there can be accumulation of calcium as hard bumps underneath the skin in the region of the rash. The skin may break open and become very itchy, to the point of disturbing sleep.

The other principle symptom, which usually appears after the rash, but which can also be coincident with the rash, is muscle weakness. The muscles most often affected are those that are near the central part of the body, such as muscles of the chest and the upper arms and legs. As the disease progresses, muscles toward the outer parts of the arms and legs can weaken. As well, the affected muscles can become sore and painful to the touch.

The muscle weakness can make it hard for the affected person to get up from a sitting position, climb up stairs, lift even moderately heavy objects, and to reach up over their head. Swallowing can become difficult. People may also feel tired, lose weight, and develop a slight fever.

Except for the presence of rash, the symptoms of dermatomyositis are virtually the same as a related disease known as polymyositis (inflammation of many muscles). In about 40% of those with dermatomyositis, only the skin is affected. In these people, the disease can also be called amyopathic dermatomyositis (ADM), or DM sine myositis.

Diagnosis

Diagnosis is based on the presence of skin rash, muscle weakness, and higher than normal levels of some muscle enzymes (due to breakdown of muscle cells). A muscle biopsy , in which a sample of muscle is obtained, can reveal inflammation and the death of muscles cells associated with the weakening muscle.

Because of the presence of cancer in a significant proportion of elderly people who develop the disease, diagnosis is often accompanied by procedures like a chest x ray, mammogram in women, prostate examination in men, and sometimes a scan of the abdomen using the technique of computed tomography.

Treatment team

The treatment team for a case of dermatomyositis is typically made up of the family physician, neurologist , physical therapists, and family members or caregivers. Sometimes the team also includes a dermatologist (specialist in the structure, functions, and diseases of the skin) and a rheumatologist (specialist in conditions that cause swelling or pain in the muscles and joints).

Treatment

Treatment principally consists of therapy with glucocorticoid medications, which help quell an immune response that can exacerbate the rash. The steroid that is typically given is prednisone. In some people, this drug is not effective or tolerated well. Alternate drugs that can be given are azathioprine and methotrexate. An immune compound called immunoglobulin can also be given intravenously.

Clinical trials

As of April 2004, there are seven clinical trials related to dermatomyositis or other related conditions recruiting participants in the United States. Some of the trials are evaluating new treatments such as novel drugs and irradiation. Other trials are trying to uncover how the disorder develops in children. Updated information about ongoing trials can be found at the National Institutes of Health website for clinical trials at <http://www.clinicaltrials.org>.

As well as the clinical trials, research is being undertaken to unravel the mechanisms of development of the disease, with a goal to prevent, treat, and ultimately, cure dermatomyositis.

Prognosis

The disease is seldom fatal, although muscle weakness can persist for life. Most cases of dermatomyositis do respond to therapy, which improves a person's outlook. However, the prognosis may not be as good if the disease is accompanied by heart or lung problems. In the latter cases, a person may become confined to a wheelchair. On rare occasions, heart or lung muscles weakened by dermatomyositis can cause death.

Special concerns

Approximately one-third of older people who develop dermatomyositis also have cancer. In some cases, the cancer may not yet be diagnosed. Therefore, a thorough physical examination of all body systems is important after receiving a diagnosis of dermatomyositis.

Resources

BOOKS

Parker J. N., and P. M. Parker. The Official Parent's Sourcebook on Dermatomyositis: A Revised and Updated Directory for the Internet Age. San Diego, Icon Group International, 2002.

PERIODICALS

Grogan, P. M., and J. S. Katz. "Inflammatory Myopathies." Current Treatment Options in Neurology (March 2004): 155161.

OTHER

Callen, J. P. "Dermatomyositis." eMedicine. April 14, 2004 (May 27, 2004). <http://www.emedicine/com/derm/topic98.htm>.

"NINDS Dermatomyositis Information Page." National Institute of Neurological Disorders and Stroke. April 12, 2004 (May 27, 2004). <http://www.ninds.nih.gov/health_and_medical/disorders/dermato_doc.htm>.

ORGANIZATIONS

American Autoimmune Related Diseases Association. 22100 Gratiot Avenue, Eastpointe, MI 48201-2227. (586) 776-3900 or (800) 598-4668; Fax: (586) 776-3903. aarda@aol.com. <http://www.aarda.com>.

Myositis Association. 1233 20th Street, NW, Washington, DC 20036. (202) 887-0084 or (800) 821-7356; Fax: (202) 466-8940. tma@myositis.org. <http://www.myositis.org>.

National Institute for Neurological Diseases and Stroke (NINDS), 6001 Executive Boulevard, Bethesda, MD 20892. (301) 496-5751 or (800) 352-9424. <http://www.ninds.nih.gov>.

National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). 31 Center Dr., Rm. 4C02 MSC 2350, Bethesda, MD 20892-2350. (301) 496-8190 or (877) 226-4267. NIAMSinfo@mail.nih.gov. <http://www.niams.nih.gov>.

National Organization for Rare Disorders. 55 Kenosia Avenue, Danbury, CT 06813-1968. (203) 744-0100 or (800) 999-6673; Fax: (203) 798-2291. orphan@rarediseases.org. <http://www.rarediseases.org>.

Brian Douglas Hoyle, PhD

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Dermatomyositis

Dermatomyositis

Definition

Dermatomyositis (DM) is a rare inflammatory muscle disease that leads to destruction of muscle tissue usually accompanied by pain and weakness.

Description

Dermatomyositis is one of a group of three related diseases called inflammatory myopathies. The other two are polymyositis and inclusion-body myositis. These diseases are rare; only about 20,000 people in the United States have dermatomyositis. Another estimates suggest that DM occurs in about 5.5 individuals out of every one million. The disease is of unknown origin and can develop in children and adults. Most often individuals either develop DM either between the ages of five and 14 or they do not develop it until they are over age 45. In all age groups, females are twice as likely to develop the disease than males. Although DM causes pain and weakness, it is not necessarily life threatening. However, adults, but not children, who develop DM have an increased risk of developing cancer and should be screened for malignancies regularly.

Causes and symptoms

The exact cause of dermatomyositis is unknown. It is an autoimmune disease. In a healthy body, cells of immune system attack only foreign or defective cells in the body to protect it from disease. In an autoimmune disease, the immune system attacks normal body cells. In the case of DM, immune system cells attack healthy cells of small blood vessels in the muscle and skin. Over time, this causes muscle fiber to shrink and sometimes cuts off blood supply to the muscle. DM tends to develop in muscles closest to the center of the body.

As yet, there is no clear explanation of what causes an individual to develop DM. It is thought that the disease may be triggered by a virus or exposure to certain drugs or vaccines. According to the Muscular Dystrophy Association, recent research suggests developing DM may be related to the mixing of blood cells that sometimes occurs between the mother and fetus during pregnancy. The disease is not directly inherited, although there may be some genetic sensitivity toward whatever triggers it.

Often the first sign of DM is the development of a patchy, scaly, violet to dark red skin rash on the face, neck, shoulders, upper chest, knees, or back. Often the rash appears before any signs of illness or muscle weakness. About 40% of children and teens develop hard, painful bumps under the skin that are deposits of calcium, a mineral used in bone formation. This condition, called calcinosis, is much less common in adults.

Muscle weakness, especially in the upper arms, hips, thighs, and neck, becomes apparent in activities such as climbing stairs or reaching up over the head. This weakness develops after the rash appears. Some people have difficulty swallowing and chewing when the muscles of the face and esophagus are affected. Individuals may also feel tried, weak, have a low-grade fever, weight loss, and joint stiffness. Some individuals have the rash for years before they progress to these symptoms, while in others the onset of symptoms is rapid. In children the development of symptoms is almost always gradual, making diagnosis especially difficult.

Diagnosis

DM can be difficult to diagnose, and often the first doctor an individual sees is a dermatologist for treatment of the rash and then is referred to a rheumatologist, specialist in internal medicine or neurologist when DM is suspected. Many tests may be done to rule out other diseases before a firm diagnosis is made. A blood test is done to measure the level of creatine kinase. Creatine kinase is an enzyme found in muscle tissue. When muscle is damaged, this enzyme leaks out into the blood. An increased level of creatine kinase in the blood suggests DM as a possible diagnosis. Another blood test may be done to test for specific immune system antibodies. Antibodies are proteins made in response to material the body thinks is foreign.

An electromyogram (EMG) is a test that measures electrical activity in muscles as they contract. Individuals with inflammatory myopathies usually have distinct patterns of electrical activity in the affected muscles. However, up to 15% of people with DM have normal electromyogram readings, so this test is not definitive. The definitive test is a muscle biopsy. The doctor takes a small sample of muscle tissue and examines it under a microscope. From this sample, the doctor can differentiate DM from other inflammatory myopathies and other muscle wasting diseases.

Treatment

The goal of treatment is to improve muscle strength and allow the individual to participate in normal daily activities. Individuals are given steroid drugs (prednisone, corticosteroids ) that suppress the immune system. Over time, these drugs often produce undesirable side effects, so treatment is usually begun with a large dose, then tapered to the minimum dose needed for maintenance. People who do not respond well to steroid treatment may be treated with other immunosuppressive drugs or intravenous immunoglobulin. Individuals with DM are advised to avoid exposure to the sun, as sunlight worsens the skin rash. Physical therapy is often helpful in keeping joints from stiffening and freezing. Moderate exercise is also recommended.

Alternative treatment

A healthy diet high is recommended for all individuals with supplemental protein for those with severe muscle damage.

Prognosis

The course of DM is highly variable. In about 20% of people, the disease spontaneously goes into remission and individuals are able to lead symptom-free lives for long periods. On the other hand, in about 5% of individuals the disease progresses to death because of heart and lung involvement. The majority of people continue to have some symptoms and require long-term treatment, but their degree of daily activity varies greatly.

Serious complications from DM include involvement of the muscles of the heart and lungs, difficulty eating and swallowing, and a tendency to develop cancer. This association is seen only in adults and not in children. Individuals over age 60 are more likely to have serious complications than younger individuals.

Prevention

There is no known way to prevent this disease.

Resources

PERIODICALS

Koler, Ric A. and Andrew Montemarano. "Dermatomyositis." American Family Physician, 24, no. 9 (1 November 2001) 15651574 [cited 16 February 2005]. http://www.aafp.org/afp/2001101/1565.html.

ORGANIZATIONS

American Autoimmune Related Disease Association. 22100 Gratiot Avenue, Eastpointe, East Detroit, MI 48201-2227. 800-598-4668. http://www.aarda.org.

Muscular Dystrophy Association. 3300 East Sunrise Drive, Tucson, AZ 85718-3208. 800-572-1717. http://www.mdausa.org

Myositis Association. 1233 20th Street, NW, Washington, DC 20036. 800-821-7356. http://www.myositis.org.

National Organization for Rare Disorders (NORD). P. O. Box 1968, Danbury, CT 06813-1968. 800-999-NORD. http://www.rarediseases.org.

OTHER

Callen, Jeffrey P. Dermatomyositis, 5 December 2002 [cited 16 February 2005]. http://www.emedicine.com/derm/topic98.htm.

Hashmat, Aamir and Zaineb Daud. Dermatomyositis/Polymyositis, 16 January 2004 [cited 16 February 2005]. http://www.emedicine.com/neuro/topic85.htm.

KEY TERMS

Immunoglobulin Material containing specific antibodies to fight disease that can be injected into an individual to fight infection.

Inflammation An infection or irritation of a tissue.

Myopathy Relating to muscle tissue.

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dermatomyositis

dermatomyositis (der-mă-toh-my-oh-sy-tis) n. an inflammatory disorder of the skin and underlying tissues, including the muscles. A bluish-red skin eruption occurs on the face, scalp, neck, shoulders, and knuckles and is later accompanied by severe swelling. The condition is one of the connective-tissue diseases; it is often associated with internal cancer in adults, though not in children.

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