myositis

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Myositis

 

Definition

Myositis is a rare disease in which the muscle fibers and skin are inflamed and damaged, resulting in muscle weakness. There are several types of myositis that affect different parts of the body.

Description

The persistent inflammation that is associated with myositis develops slowly over weeks to months and often years, with progressive weakening of the muscles. Later in the course of the disease development muscle wasting or shortening (contracture) may develop. Myositis can range in severity from mild to debilitating.
The forms of myositis include:
  • Polymyositis (PM) inflames and weakens muscles in many parts of the body, and especially those parts closest to the trunk. With polymyositis, dysphagia (difficulty, discomfort or pain in speaking or swallowing), fatigue, and pain in the muscles are common. PM rarely affects people under the age of 20, with the peak onset between the ages of 30 and 60.
  • Dermatomyositis (DM) affects both the muscle fibers and skin by damaging the tiny blood vessels (capillaries) that supply blood to the muscle and skin, resulting in muscle weakness, pain, and fatigue. In addition the affected person develops a distinctive patchy, reddish rash on the eyelids, cheeks, bridge of the nose, back or upper chest, elbows, knees, and knuckles. There may also be hardened, tender bumps (possibly caused by inflammation of fat) under the skin. DM can occur at any age and is more common in females than males.
  • Inclusion Body Myositis (IBM) typically begins after age 50, and is characterized by gradual weakening of muscles throughout the body, including the wrists or fingers, development of dysphagia, and atrophy of forearms and/or thigh muscles. Unlike the other types of myositis, IBM occurs more often in men than women, and also does not respond very well to drug therapy.
  • Juvenile myositis (JM) involves muscle weakness, skin rash, and dysphagia in children. A common characteristic of JM is the formation of calcium deposits in the muscle (calcinosis). These deposits are hard and sometimes painful lumps of calcium under the skin that appear on the child's fingers, hands, elbows, and knees. Painful sores may appear if the lumps break through the skin. The child may also suffer from contractures, which is muscle shortening that results in joints staying bent. About half of the children with JM will have pain in their muscles.
Myositis is rare, affecting about 10 in one million people each year. DM and PM affect mostly women in the forties and fifties but men and children can also affect be affected, some at a young age (between the ages of 5 and 15). About 40,000 people in the United States may have this disease, with about 3,000 to 5,000 children affected.

Causes and symptoms

Myositis is thought to be an autoimmune disease. The body normally fights infections and disease by producing antibodies and white blood cells called lymphocytes in a process called the immune response. In an autoimmune disease, the immune response is overactive, and the immune system attacks and destroys the body's own normal healthy tissues. There is no known cause to the autoimmune response that results in myositis. However, investigators are studying whether the disease is triggered by such environmental agents as the organism that causes toxoplasmosis, Toxoplasma gondii, the Lyme disease organism, Borrelia burgdorferi, the coxsackievirus, or by food allergies. Some cases of IBM are thought to be inherited.
The first symptoms of most types of myositis are weakness and pain in the muscles of the hips and shoulders. The affected person may have trouble getting up from a chair, lifting the arms above the head, or climbing stairs, and may be too tired to walk or stand. DM and PM mostly affects muscles that are close to and within the trunk of the body, while IBM involves a wider range of muscles. Myositis may make it difficult for the person to speak or swallow. When the disease affects the lungs or chest muscles, the person may have difficulty breathing. If the person has DM, they may develop characteristic rashes. Other symptoms may include fever and joint pain and swelling.
The first signs of JM is usually a red and patchy skin rash and/or a red or purplish rash on the eyelids or cheeks that look like allergies. Weak muscles may develop at the same time as the rash, or may develop days, weeks, or months after the appearance of the rash. Other symptoms of JM include falling, a weaker voice (dysophonia), or dysphagia. Calcinosis usually develops later during the course of the disease.

Diagnosis

Myositis can a difficult disease to diagnose, because it is rare, because the symptoms develop slowly, and because it can be mistaken for other diseases causing muscle weakness such as limb-girdle muscular dystrophy. Many cases of myositis go undiagnosed for years. The health care provider must rule out other conditions such as hypothyroidism, toxin exposure, drug reactions, and genetic disorders that can also affect muscles. The physical examination will include a complete medical history focusing on symptoms and when they occurred, and blood tests for autoantibodies and muscle enzymes (for example, creatine kinase (CK), which when present in the blood indicates muscle damage). Specialized tests may also be performed, including:
  • an electromyogram, which measures the electrical pattern of the muscles
  • a muscle biopsy, in which a small piece of muscle is removed, stained, and examined by microscopic techniques to determine if muscle fibers are damaged and whether the muscle fibers are being infiltrated by cells of the immune system
  • magnetic resonance imaging (MRI) to identify areas of muscle inflammation.

Treatment

There is no cure for myositis. However, prompt and aggressive treatment may reduce muscle inflammation and prevent muscle weakness from progressing. Because of the many different kinds of symptoms and a wide range of reactions to different drugs, each person's treatment for myositis should be individualized.
Drugs that are used for treatment include corticosteroids, such as prednisone, to reduce inflammation and improve the body's reaction to infections. Corticosteroids are usually taken in the form of pills, but may also be injected. The amount of creatine kinase (CK) levels in the blood are monitored to determine how well the medicine is working. Corticosteroids may produce a number of side effects, such as weight gain, difficulties in fighting infections, psychiatric changes, sleeping troubles, water retention, bone thinning, facial swelling, diabetes, and cataracts. Corticosteroid therapy usually leads to improvement in myositis symptoms within two to three months, after which the dose can be lowered to avoid the side effects. If the dose of corticosteriods is going to be reduced, it is essential to lower the dose over a period of time.
Immunosuppressant drugs are used to slow down the immune system's attack on healthy tissue and improve skin rashes. Persons may be prescribed these drugs to control myositis if they are unable to tolerate corticosteroids or if the corticosteroids are not accomplishing the desired degree of treatment. Immunosuppressant drugs may also be used in conjunction with corticosteroids so that lower doses of corticosteroids can be used. Immunosuppressant drugs include azathioprine, methotrexate, cyclosporine, tacrolimus, etanercept, and mycophenolate mofetil.
Intravenous immunoglobulin (IVIg) appears to aid in improving muscle strength in many persons with myositis, particularly those with DM. It may be less effective in PM, and its role in treating IBM requires more study, although it has been shown to help some patients with IBM if they are diagnosed early. Immunoglobulins are normal proteins in the blood that attack anything foreign in the body, such as viruses and bacteria. IVIg is made from donated blood plasma from people with normal immune systems. Side effects from the the use of IVIg include headache and flu-like symptoms.
Topical cream or ointment forms of some of the medicines, such as prednisone and tacrolimus, can be used to heal and soothe the rash associated with DM. Non-steriodal anti-inflammatory drugs (NSAIDS) such as aspirin or ibuprofen can be used for pain relief. Calcinosis can be treated with prednisone, plaquenil (also called hydroxychloroquine), intravenous immunoglobin (IVIG), cyclosporine, and methotrexate.
After drug treatment results in improvement, the affected person begins a program of regular stretching exercises to maintain range of motion in the weakened arms and legs. Physical therapy may be used to prevent permanent muscle shortening. Whirlpool baths, heat, and gentle massages may also provide relief. Adequate rest is necessary, and affected persons should take frequent breaks throughout the day and limit their activity.
Patients with throat problems should be evaluated by a speech therapist who can evaluate the swallowing-related problems and make recommendations regarding diet changes and safe swallowing techniques.
Before a woman with myositis becomes pregnant, she should discuss the medicines that she is taking with her health care provider and evaluate the possible risks that she and the baby face if she does become pregnant. Many of the drugs used in the treatment of myositis may be harmful to the fetus or to a breastfed baby.
It is recommended that a doctor experienced in the treatment of myositis, assisted by a rheumatologist, dermatologist, or neurologist, be consulted. Oftentimes a patient may have to be treated at a major medical center, where the disease has been seen and treated before.

Alternative treatment

Various supplements may be used in conjunction with traditional treatment to offset side effects of conventional drug treatment. The use of these suppplements should be approved by the primary health care provider.
Immunosuppressant drugs such as methotroxate and cyclophosphamide increase the risk of infection, so a healthy well-balanced diet is required. Methotroxate impairs the body's ability to absorb folic acid, so foods high in folic acid, such as leafy green vegetables, fruits, and folate-fortified breads and cereals are recommended. The use of folate supplements may also be recommended by the health care provider. Vitamins C and E can be used to help with the pain and infections associated with calcinosis.
Corticosteroids may have multiple side effects when taken for long periods of time at high doses. Calcium and Vitamin D are recommended to lower the risk of osteoporosis, a common side effect of prednisone use. Hypertension and fluid retention may be controlled by a diet low in salt. Steroid-induced diabetes (hyperglycemia) can be aided by a diet low in sugar and other simple carbohydrates. Proteinuria, in which the body breaks down protein faster than normal, may mean that more protein should be included in the diet.
Weight gain associated with the use of corticosteroids can be managed by the use of the DASH (Dietary Approach to Stop Hypertension) diet, which is high in fruits, vegetables, dietary fiber, and low-fat dairy products. Information concerning this diet, developed by the National Institutes of Health, can be found at [www.nhlbi.nih.gov/health/public/heart/hbp/dash/]. Weight gain can overtax weakened muscles and should be avoided if possible.

Prognosis

The progression of PM and DM varies from person to person, but the lifespan of an affected person is not usually significantly affected. DM responds more favorably to therapy than PM. Overall, many patients do improve and have a functional recovery. About half of the patients recover and can discontinue treatment within 5 years of beginning treatment. In children the chances of a cure are better than in adults, although some children do suffer a relapse. Of the remaining 50%, about 20% will still have the active disease and will require ongoing treatment, while up to 30% may have some remaining muscle weakness. However, IBM is disabling, and most patients will require the use of an assistive device such as a cane, walker, or wheel chair. The older the patient is when contracting IBM, the more rapidly the disease progresses.

Prevention

There is no known way to prevent myositis.

Resources

Books

Kilpatrick, James R. (Compiler). Coping with a Myositis Disease. Written by Myositis Patients Telling Their Personal Story of Dealing with this Muscle Disease. Athens, TX: Kilpatrick Publishing Company, 2000.
Icon Health Publications. Myositis: A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet Resources. San Diego, CA: Icon Health Publications, 2004.
Icon Health Publications. The Official Patient's Sourcebook on Dermatomyositis: A Revised and Updated Directory for the Internet Age. San Diego, CA: Icon Health Publications, 2002.
Icon Health Publications. The Official Patient's Sourcebook on Inclusion Body Myositis: A Revised and Updated Directory for the Internet Age. San Diego, CA: Icon Health Publications, 2002.

Organizations

Muscular Dystrophy Association—USA, National Headquarters. 3300 E. Sunrise Drive, Tucson, AZ 85718. Telephone: (800) 572-1717. Web site: www.mdausa.org/
Myositis Support Group. 205 Laurel Road, Athens, TX 75751. Telephone: (903) 675-6825. Fax: (903) 675-6823. Web site: www.myositissupportgroup.org/
The Myositis Association (TMA). 1233 20th St. NW, Suite 402Washington, DC 20036. Telephone: (202) 887-0082; Fax: (202) 466-8940; Web site: www.myositis.org/

Other

Progressive Management. 21st Century Complete Medical Guide to Myositis, including Dermatomyositis and Polymyositis, Authoritative Government Documents, Clinical References, and Practical Information for Patients and Physicians. (CD-ROM). Washington, DC: Progressive Management, 2004.

Key terms

Coxsackievirus — Enterovirus causing a disease resembling poliomyelitis but without paralysis
Dysphagia — Medical term for any difficulty, discomfort or pain when swallowing
Limb-girdle muscular dystrophy — An autosomal recessive form of muscular dystrophy that appears anywhere from late childhood to middle age and is characterized by progressive muscular weakness beginning either in the shoulder or pelvic girdle; the disease usually progresses slowly with cardio-pulmonary complications in the later stages

myositis

 [mi″o-si´tis]
inflammation of a voluntary muscle; called also initis.
myositis fibro´sa a type in which there is a formation of connective tissue in the muscle.
multiple myositis polymyositis.
myositis ossi´ficans myositis marked by bony deposits in muscle.
trichinous myositis that which is caused by the presence of Trichinella spiralis.

my·o·si·tis

(mī'ō-sī'tis), [MIM*160750]
Inflammation of a muscle.
Synonym(s): initis (2)
[myo- + G. -itis, inflammation]

myositis

/myo·si·tis/ (mi″o-si´tis) inflammation of a voluntary muscle.
myositis fibro´sa  a type in which connective tissue forms within the muscle.
inclusion body myositis  a progressive inflammatory myopathy primarily involving muscles of the pelvic region and legs.
multiple myositis  polymyositis.
myositis ossi´ficans  myositis marked by bony deposits or by ossification of muscle.
proliferative myositis  a benign, rapidly growing, reactive, nodular lesion similar to nodular fasciitis, but characterized by fibroblast proliferation within skeletal muscle.
trichinous myositis  that due to the presence of Trichinella spiralis.

myositis

(mī′ə-sī′tĭs)
n.
Inflammation of a muscle, especially a voluntary muscle, characterized by pain, tenderness, and sometimes spasm in the affected area.

myositis

[mī′əsī′tis]
inflammation of muscle tissue, usually of voluntary muscle. Causes of myositis include infection, trauma, and infestation by parasites. Kinds of myositis include epidemic myositis, myositis fibrosa, parenchymatous myositis, polymyositis, and traumatic myositis. Also called myitis [mī·ī′tis] . Compare fibromyalgia.

myositis

A general, nonspecific term for inflammation of muscle.

myositis

Myitis Muscle inflammation. See Dermatomyositis, Inclusion body myositis.

my·o·si·tis

(mī'ō-sī'tis)
Inflammation of a muscle.
Synonym(s): initis (2) .
[myo- + G. -itis, inflammation]

myositis

Inflammation of muscle. This may occur as a result of a Coxsackie virus infection as in BORNHOLM'S DISEASE, or it may be a feature of DERMATOMYOSITIS, or a response to the parasitic worm Trichinella spiralis that settles in muscle, or an AUTOIMMUNE reaction affecting the external eye muscles in thyroid disease.

my·o·si·tis

(mī'ō-sī'tis) [MIM*160750]
Inflammation of a muscle.
[myo- + G. -itis, inflammation]

myositis

(mī´əsī´tis),
n an inflammation of muscle tissue, usually of the voluntary muscles. Causes of myositis include infection, trauma, and infestation by parasites.

myositis

inflammation of a voluntary muscle. Causes heat, swelling, pain and lameness if a limb is affected. Trauma is the common cause, especially in racing and work horses. Blackleg is a specific myositis. See also polymyositis.

atrophic myositis
a form of masticatory myositis in dogs. There is a chronic, progressive atrophy and fibrosis of the masticatory muscles of dogs which finally makes it impossible for the mouth to be opened wider than a few inches.
eosinophilic myositis
1. a form of masticatory myositis seen in German shepherd dogs. It is acute, often recurrent, and there is painful, bilaterally symmetrical swelling of the masticatory muscles, mainly temporals and masseters. Often there is an eosinophilia found in the hemogram. Occasionally other muscles are also involved. There is a progressive atrophy and fibrosis of the muscles, frequently resulting in an inability to open the mouth. In the latter it may be confused clinically with atrophic myositis (above).
2. a lesion found at meat inspection. It reduces the value of the carcass. The cause is unknown.
familial myositis
see canine familial dermatomyositis.
myositis fibrosa
a type in which there is formation of connective tissue in the muscle.
masticatory myositis
see atrophic myositis and eosinophilic myositis (above).
maxillary myositis
a slowly developing myogenic degeneration of the muscles of the jaw in horses.
multiple myositis
polymyositis.
myositis ossificans
a generalized myositis with dystrophic ossification in muscle. It occurs in pigs, in which it may be familial, and rarely in dogs and cats.
trichinous myositis
caused by the presence of Trichinella spiralis.
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