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Dermatomyositis

DM

What is Dermatomyositis?

Dermatomyositis is a rare inflammatory muscle disease that primarily strikes children ages 5 to 15 and adults in their late 40s to early 60s. It causes muscle weakness and a distinctive skin rash. Women are much more likely than men to experience the disease. When it affects children, this disease is sometimes known as juvenile dermatomyositis.

Myositis is a term that indicates swelling of the muscles for any reason, including injury, infection, exercise, the effect of certain medicines or other causes. In most cases, myositis is a temporary condition that resolves when the muscles are allowed to rest, or when the underlying condition is treated.

However, in some cases the swelling is part of a chronic disorder and does not resolve quickly. Dermatomyositis is among a group of disorders classified as inflammatory myopathies. All of these diseases involve the muscles that cover the skeleton. Dermatomyositis occurs as a result of inflammation in the blood vessels under the skin and in the muscles, a condition known as vasculitis.

How is it diagnosed?

Patients who show any signs of muscle weakness or unusual rash should be seen by a physician. The earlier dermatomyositis is diagnosed, the more effective treatment is likely to be. Early diagnosis is especially important because it helps prevent calcinosis, a disorder that involves deposits of calcium in the muscles, skin and connective tissues. It occurs late in dermatomyositis and is more likely to appear in children than adults. Once calcinosis forms, it can be difficult to treat. The skin-related signs and symptoms of dermatomyositis may be less apparent in patients with dark skin. This can lead to a delay in diagnosis in these individuals.

Dermatomyositis can be difficult to diagnose because it mimics many other conditions. To diagnose dermatomyositis, a physician will perform a complete physical examination and compile a thorough medical history. The patient will be examined for the type of rash that is commonly associated with dermatomyositis. The physician will ask the patient about when the signs of skin rash or muscle weakness first appeared and its progression.

The physician may also test the health of a patient’s muscle tissue. This can be assessed in several ways. Electromyography uses a thin needle electrode that is inserted into a muscle and records electrical activity as the patient relaxes or tightens the muscle. Various muscles are normally tested. In addition, a blood test can reveal elevated levels of muscle enzymes such as creatine kinase and aldolase.

A muscle biopsy allows the physician to surgically remove a small sample of muscle tissue that is then analyzed in a laboratory. The presence of abnormal proteins or enzyme deficiencies may indicate dermatomyositis. Finally, an imaging technique known as magnetic resonance imaging (MRI) provides a cross-sectional image of the patient’s muscle. MRIs use a combination of a magnetic field and radio waves to create these images, which may reveal muscle inflammation.
Several other medical conditions are also closely associated with dermatomyositis and may be diagnosed by a physician. These include:

  • Cardiovascular disease. In some cases, the heart muscle may become inflamed (myocarditis). Rarely, congestive heart failure and heart rhythm problems (arrhythmias) may occur.
  • Lung disease. Interstitial lung disease is sometimes associated with dermatomyositis. This is a group of disorders that cause scarring of lung tissue, making lungs stiff and inelastic (fibrosis).
  • Other connective tissue diseases. Conditions such as lupus, rheumatoid arthritis, scleroderma and Sjogren's syndrome are all associated with dermatomyositis.
  • Raynaud's phenomenon. A condition in which the fingers, toes, cheeks, nose and ears turn pale when exposed to cold temperatures.
  • Cancer. Cancers of the lungs, breasts, ovaries and gastrointestinal tract are associated with dermatomyositis that occurs in adults, especially those older than 60. These cancers rarely occur in children. Because there is a high correlation between dermatomyositis in adults and cancer, physicians will always look for a malignancy in an adult with the disease.

How is dermatomyositis treated?

There is no cure for dermatomyositis. However, proper treatment can help patients to improve muscle strength and function as well as the appearance of their skin. Early treatment is key to preventing complications in children. Medications are often used to treat the condition. Children may take these medications for a period of one to three years before symptoms fade or disappear altogether. In general, adults are less likely to experience complete recovery and may remain on low-dosage medications indefinitely to control symptoms.

Medications used to treat dermatomyositis include:

Corticosteroids

Medications that suppress the immune system and help reduce inflammation of the muscles and skin. In some cases, these drugs are taken orally whereas in others, they are applied to the skin (topical). Initial dosage levels may be high before they are gradually reduced as the medication begins working. Corticosteroids must be used carefully, as they can have serious side effects including loss of bone density (osteoporosis), weight gain, diabetes, increased risk of some infections, mood swings, cataracts, high blood pressure, redistribution of body fat and muscle weakness. A physician may recommend that some patients take calcium supplements to help maintain their bone density while they take corticosteroids.

Immunosuppressants

Immunosuppressive drugs are sometimes prescribed when corticosteroids do not adequately control symptoms. They may be used on their own or in combination with corticosteroids.

Antimalarial medications

These drugs can help treat persistent rash. However, they cause side effects in some patients that mimic dermatomyositis itself. These include rash and muscle weakness.
Various medications – including corticosteroids – may be used to treat calcinosis. It may take four months or longer before existing calcium lumps stop growing and new calcium deposits stop forming. In some cases, existing lumps do not disappear even after treatment.

Patients may also benefit from taking over-the-counter (OTC) pain relievers. When OTC drugs fail to relieve the pain and discomfort associated with dermatomyositis, stronger pain relievers may be prescribed.

In addition, other treatments may be employed by patients with dermatomyositis. Physical therapy can help children to improve their strength and flexibility. It also helps the patient preserve muscle function and prevents muscle wasting. Regular exercise can help prevent contractures, which occur when the muscle shortens, forcing the joint to stay bent. Surgery may be used to remove calcium deposits from children or other patients who develop calcinosis.

Patients with dermatomyositis often have skin that is extremely sensitive to the sun. Therefore, it is urged that patients wear sunscreen even on cloudy days. Patients also are urged to moisturize the skin frequently and to use soaps that do not have alcohol so they will not dry out the skin.

Medications

Information
Brand
Generic
Label
Prednisone
Deltasone
Prednisone
Off-Label

Imuran (Azathioprine), Prograf (Tacrolimus), Rheumatrex (Methotrexate)


What might complicate it?

Individuals with dermatomyositis have an increased risk of developing a cancer. The malignancy may be present along with the initial symptoms or may not develop until later. The steroids used to suppress the disease and improve the weakness can cause muscle weakness if given in too high a dose, so the steroid dose requires careful adjustment.

Predicted outcome

For those individuals who respond to therapy, expected outcome is decreased severity or disappearance of symptoms (remission). The disease is disabling for individuals who do not respond.

Alternatives

Similar disorders causing muscle weakness are scleroderma, lupus, and rheumatoid arthritis. Other disease possibilities are hyper and hypothyroidism, chronic inflammatory polyneuropathy, multiple sclerosis, myasthenia gravis, Eaton-Lambert disease, and amyotrophic lateral sclerosis. Many drugs and alcohol can also produce muscle weakness. The rash of dermatomyositis can be similar to lupus, psoriasis, lichen planus, and mycosis fungoides.

Appropriate specialists

Rheumatologist, oncologist (if cancer is present), neurologist, physiatrist, and dermatologist.

Last updated 7 July 2021