NORD gratefully acknowledges Kristina Bundra, Pharm. D, NORD Editorial Intern, and Chester V. Oddis, MD, Professor of Medicine, University of Pittsburgh School of Medicine, for assistance in the preparation of this report.
Dermatomyositis is a type of inflammatory myopathy characterized by inflammatory and degenerative changes of the muscles and skin. Associated symptoms and physical findings may vary widely from case to case as patients may present differently. Muscle abnormalities may begin with aches and weakness of the muscles of the trunk, upper arms, hips, and thighs (proximal muscles). Muscles may be stiff, sore, tender and, eventually, show signs of degeneration (atrophy). Affected individuals may experience difficulty in performing certain functions, such as raising their arms and/or climbing stairs or develop speech and swallowing difficulties. Skin abnormalities associated with dermatomyositis often include a distinctive reddish-purple rash (heliotrope rash) on the upper eyelid or across the cheeks and bridge of the nose in a "butterfly" distribution and on the forehead and scalp. Other characteristic rashes include scaling and redness of the knuckles, elbows, knees, and/or other extensor regions (Gottron papules and sign); an abnormal accumulation of fluid (edema) in body tissues surrounding the eyes; and/or other features. The symptoms of childhood (juvenile) dermatomyositis (JDM) are similar to those associated with the adult form of the disorder. However, onset is usually more sudden. In addition, abnormal accumulations of calcium deposits (calcifications) in muscle and skin tissues as well as involvement of the digestive (gastrointestinal [GI]) tract are more common in JDM.
The inflammatory myopathies are a group of diseases that involve chronic muscle inflammation and weakness. They are thought to be autoimmune diseases, meaning the body’s natural defenses (antibodies, lymphocytes, etc.) against invading organisms suddenly begin to attack perfectly healthy tissue for unknown reasons, leading to inflammation or swelling.
In those with dermatomyositis, the onset of symptoms may be gradual (insidious) or sudden (acute). The symptoms often wax and wane for no apparent reason.
The major symptom of the disorder is muscle weakness, most often affecting the trunk and muscles closest to the trunk (i.e., proximal muscles), such as the hips, thighs, shoulders, upper arms, and neck. The affected muscles may be stiff, sore, and/or tender and, eventually, may show signs of degeneration and muscle wasting (atrophy). Muscle weakness and degeneration progress and may lead to an awkward manner of walking (gait) and a gradual inability to perform certain tasks, such as lifting the arms, climbing steps, or dressing. Characteristic signs may include an inability to raise the head from the pillow when lying down or to rise unassisted from the floor. In some people with the disorder, involvement of muscles of the neck, tongue, and/or throat may eventually result in difficulties swallowing (dysphagia) and/or articulating speech (dysphonia). In rare cases, weakening of muscles of the chest wall and diaphragm may cause respiratory difficulties, potentially leading to life-threatening complications without prompt, appropriate treatment. In addition, in some with chronic, long-term disease, certain joints may become fixed in a permanently bent (flexed) position (contractures) and lead to problems in walking.
Individuals with dermatomyositis also develop characteristic skin changes that, in some cases, may precede muscle weakness. These characteristic skin changes may be the only sign of dermatomyositis at the start in up to 40% of people. Skin abnormalities often include a distinctive reddish-purple or lilac (i.e., heliotrope) rash that may be present on the upper eyelids (heliotrope eyelids); the forehead; the cheeks and bridge of the nose (“butterfly rash”); and/or other regions. In addition, affected skin on the extensor surfaces of certain joints, such as the knuckles, elbows, knees, or other regions, may tend to become scaly, with central areas of tissue loss (atrophy) that lack or have increased pigmentation (Gottron sign). A “dusky” reddish (erythematous) rash may also develop on the upper arms, upper legs, and upper trunk. The rash tends to be itchy and can lead to trouble sleeping for many people. Although the skin rashes frequently fade completely, they may be followed by brownish discolorations (hyperpigmentation) of the skin, atrophy, scarring, and/or loss of color (depigmentation) of patches of skin (vitiligo). Dermatomyositis may also be associated with distinctive changes of the nails that can include: bluish-red, scaling lesions around the base of the nails; reddish “shininess” of the nail folds; abnormal widening (dilation) of capillaries of the nailbeds; or other findings. Additional skin manifestations may include an abnormal accumulation of fluid in body tissues (edema) surrounding the eyes (periorbital area) and in other facial regions; an increased sensitivity to light (photosensitivity); and/or other findings. In some cases of long-term chronic disease, atrophic changes may result in binding of skin to underlying tissue structures. Some affected individuals, particularly children, may also have abnormal accumulations of calcium deposits (calcinosis) in affected muscles and tissues under the skin (subcutaneous tissues), potentially leading to contractures and localized muscle atrophy. Itching and scaling lesions may develop on the scalp leading to significant hair loss.
Some individuals with dermatomyositis may also develop symptoms such as low-grade fever, a general feeling of ill health (malaise), shortness of breath (dyspnea), pain in multiple joints (polyarthralgia), weight loss, and/or other abnormalities. In some cases, affected individuals, particularly those who have muscle inflammation (myositis) in association with other connective tissue disorders, experience Raynaud phenomenon. This is a condition in which sudden contraction of blood vessels supplying the fingers and toes (digits) causes a temporary interruption of blood flow and associated numbness, tingling, abnormal discoloration of the digits, and pain. Episodes are most commonly triggered by exposure to cold temperatures. (For more information, choose “Raynaud” as your search term in the Rare Disease Database).
Muscle weakness and impairment may progress to affect other areas of the body, including muscles of the GI tract, within the cardiovascular system (i.e., heart, blood vessels, and blood circulation), and/or the lungs. In rare cases the heart muscle may weaken (cardiomyopathy) or irregularity of the heartbeat can occur (arrhythmias). Inflammation of the lung tissue (interstitial pneumonitis or interstitial lung disease) can result in breathing difficulties (dyspnea) and coughing. Some studies have shown plaque accumulation in the arteries (atherosclerosis) in people with dermatomyositis.
Furthermore, in some individuals with dermatomyositis, there may be an association with an underlying cancer (malignancy). Reports indicate that the malignancy may precede, occur in association with, or develop subsequent to the onset of dermatomyositis. Malignancy-associated dermatomyositis appears to occur more frequently in individuals over the age 40-50. Although there is no characteristic cancer site or type, experts indicate that underlying malignancies most commonly arise in the GI tract, lungs, breast, ovary, testis, or certain white blood cells (lymphocytes) or lymphoid tissue (i.e., certain lymphomas and leukemias, multiple myeloma). The relationship between dermatomyositis and malignancies is not fully understood.
The symptoms and physical findings associated with childhood dermatomyositis are similar to those observed in adult dermatomyositis. Onset is usually more sudden (acute) than in the adult form and often involves skin manifestations followed by muscle weakness. Calcification of muscles and tissues is more frequent and widespread in childhood dermatomyositis as compared to adult forms. The deposits have a high calcium content and tend to be firm, white, or flesh-colored nodules over bony areas which can include the elbows, knees, and extremities. These calcifications often develop within three years of diagnosis but may develop up to 20 years later. Affected children also tend to have widespread inflammation of blood vessels (vasculitis), with more frequent involvement of the GI tract. In those with GI vasculitis, associated findings may include abdominal pain; difficult, infrequent, or incomplete passing of stools (constipation); or the passage of tarry, black stools (melena) or vomiting of blood due to the development of sores or eroded areas in the lining of the GI tract (bleeding peptic ulcers). Children may also develop a tiptoe gait secondary to a stiffening of the ankles. Malignancy is rarely associated with the childhood form of dermatomyositis.
In rare cases known as dermatomyositis sine myositis, the skin abnormalities associated with dermatomyositis may occur without the associated muscle abnormalities.
The specific underlying cause(s) of dermatomyositis remain unknown. However, evidence suggests that genetic, immune, and environmental factors play some role. Underlying genetic and immune mechanisms may be suggested by various findings, including an increased frequency of certain genetically determined HLAs or “human leukocyte antigens” in individuals with the disorder. HLAs are proteins that play an important role in the body’s immune system, influence the outcome of transplantation, and appear to affect an individual’s predisposition to certain diseases. Evidence suggests that certain HLAs have an increased frequency in children and adults with dermatomyositis. However, the specific implications of such findings are not fully understood.
Dermatomyositis is thought to belong to a group of disorders in which the body’s natural immune defenses inappropriately act against the body’s own tissues (autoimmune disorders). In dermatomyositis, an abnormal immune reaction appears to lead to obstructive inflammatory changes of blood vessels within muscle, connective tissues of the skin, and other tissues; patchy degeneration, wasting (atrophy), and regeneration of muscle fibers; thinning of the outermost skin layer (epidermis); and/or other associated findings.
Reports indicate that certain infectious agents (i.e. coxsackie virus, parvovirus, echovirus, HIV, human T-cell lymphotrophic virus Type 1, and Toxoplasma and Borrelia species) have been suggested as potential triggers for dermatomyositis. Some researchers suggest that, in genetically predisposed individuals, the presence of foreign viral proteins (antigens) that are similar to some of the body’s own proteins may trigger the production of antibodies that improperly “cross-react” or act against the body’s own cells (i.e., intramuscular blood vessels), leading to the inflammatory changes and muscle tissue damage seen in dermatomyositis. Environmental factors have also been seen to play a role in cases of juvenile dermatomyositis that develop/exacerbate in the months of April and May. In addition, researchers indicate that the association of dermatomyositis with underlying malignancies in some adults may suggest an abnormal autoimmune response directed against a common antigen in muscle and the cancerous tumor. There have also been some reports in which dermatomyositis has appeared to occur following certain vaccinations or the use of particular medications (i.e., penicillamine, the statins, quinidine, and phenylbutazone). Dermatomyositis may be initiated or exacerbated following silicone breast implants or collagen injections. However, the implications of such findings remain unknown and more data is required to establish the association.
Dermatomyositis may occur at any time from infancy through approximately age 80, but most commonly it occurs between ages 40 to 60. The estimated incidence of dermatomyositis is 9.63 cases per million people. In children, the symptoms usually appear between the ages of five to 15 years. Approximately three in 1,000,000 children are affected by juvenile dermatomyositis. Females are affected by dermatomyositis twice as often as males.
Dermatomyositis may be diagnosed based upon a detailed patient history, thorough clinical examination, detection of characteristic physical findings, and certain specialized tests. Diagnostic findings include the presence of the characteristic skin rash; progressive weakness of proximal muscles; elevated levels of certain muscle enzymes (i.e., creatine kinase [CK], aldolase, aspartate aminotransferase, lactic dehydrogenase) in the liquid portion of the blood (serum) that may be suggestive of muscle inflammation; and abnormal findings on electromyography (EMG). EMG is a test that records electrical activity in skeletal (voluntary) muscles at rest and during muscle contraction. In some instances, physicians may also recommend magnetic resonance imaging (MRI), during which a magnetic field and radio waves create detailed cross-sectional images of certain tissues. In addition, muscle biopsies may sometimes be recommended to help detect certain changes that may help confirm the diagnosis. Muscle biopsy involves the removal and microscopic examination of small samples of muscle tissue. (Experts indicate that muscles recently tested with EMG should be avoided since EMG procedures may cause inflammatory changes potentially leading to false positive results upon biopsy.) Additional imaging studies may be performed to aid in the diagnosis and can include: computed tomography (CT) scanning, chest radiography, barium swallow, and ultrasound of the muscles affected.
Although the results of certain blood tests may provide helpful information suggestive of the diagnosis, such findings may be nonspecific, meaning that they may be associated with a variety of autoimmune connective tissue disorders. For example, some affected individuals may have an elevated erythrocyte sedimentation rate (ESR). ESR measures the rate that red blood cells (erythrocytes) settle to the bottom of a test tube. Because erythrocytes tend to clump together and thus settle more quickly when inflammation is present, an elevated ESR functions as a nonspecific indicator of inflammation. In some affected individuals, testing may also reveal certain antinuclear antibodies (ANAs), which are “self-antibodies” (autoantibodies) that react with antigens in the nuclei of cells. A number of specific autoantibodies or myositis-specific antibodies have been identified that may be seen in some individuals with inflammatory muscle diseases, including dermatomyositis and polymyositis, that may be helpful in classifying the disease in certain cases (i.e., anti-Jo-1 antibodies, often seen in associated lung involvement).
In some cases, additional tests may also be recommended to help detect or characterize certain abnormalities that may be associated with the disorder. For example, x-ray imaging may reveal calcifications in certain soft tissues. In addition, stool samples may be taken to detect blood, a finding suggestive of gastrointestinal involvement. Pulmonary function studies may also be conducted to assess for lung involvement.
For adults with dermatomyositis, the possibility of an underlying malignancy should be considered during basic clinical assessment. In addition to a basic, thorough physical examination, including breast, gynecologic, and/or rectal examination, screening may include routine blood testing, analysis of urine and stool, chest x-rays, mammograms in women, and/or other tests, as well as appropriate follow-up testing as required.
Diagnosis of juvenile dermatomyositis is traditionally based on the presence of the following criteria: characteristic skin rash; generalized muscle weakness; elevated muscle enzymes; myopathic changes on electromyography; and/or abnormal muscle biopsy findings.
The treatment of dermatomyositis is directed toward the specific symptoms that are apparent in each individual and thus can vary from one patient to another. Such treatment may require the coordinated efforts of a team of medical professionals, such as pediatricians or internists; physicians who specialize in the diagnosis and treatment of connective tissue disorders (rheumatologists); specialists in the functioning of the immune system (immunologists); and/or other health care professionals. In general, treatment for the muscle involvement associated with dermatomyositis requires the use of glucocorticoids. Treatment for the skin findings associated with dermatomyositis includes: sun avoidance, sunscreens, topical glucocorticoids, anti-malarial agents, methotrexate, mycophenolate mofetil, and/or intravenous immunoglobulin (IVIg).
Glucocorticoids, particularly prednisone, are widely used in the treatment of dermatomyositis and are often used first-line. Such medications, which are similar to the natural hormones produced by the outer region of the adrenal glands (adrenal cortex), are often used to reduce inflammation and associated swelling and also serve to suppress immune responses (immunosuppressive therapy). Blood levels of muscle enzyme (i.e., CK) activity are repeatedly measured to help monitor the effectiveness of such therapy. Reduction of these enzymes toward or reaching normal levels is noted in most affected adults within approximately six to 12 weeks after treatment is started, with subsequent improvement in muscle strength. When normal enzyme levels have been achieved, the dose of prednisone is usually slowly reduced (tapered). Dose levels are increased if muscle enzyme levels rise. Physicians may attempt to carefully, gradually withdraw such therapy periodically to determine whether the disease remains clinically active. In many cases, however, prolonged maintenance therapy with prednisone may be necessary. Yet reports indicate that some adults may appear to achieve a complete response. In such instances, therapy may be gradually withdrawn with careful ongoing monitoring.
Affected children may initially require high dose therapy with prednisone, which often results in a return of muscle enzyme levels toward normal levels within about one to two weeks. As with adults, decreased muscle inflammation and improved muscle strength typically follow. Dose levels may then be slowly reduced to the lowest possible dose sufficient to maintain normal enzyme levels and improve symptoms. Generally, according to experts, children with dermatomyositis may be able to discontinue prednisone after approximately two years, experiencing an apparent cessation of symptoms (i.e., remission).
High dose glucocorticoid therapy may produce adverse side effects, particularly after prolonged use, such as a decrease in bone density, causing bones to become brittle and weakened (osteoporosis); increasing, “superimposed” muscle weakness due to effects of the medication (i.e., corticosteroid myopathy); tissue swelling (edema); peptic ulcers; elevated blood pressure; elevated blood sugar levels; weight gain with fat deposits in the abdomen, face, and/or back of the neck or other findings. Physicians may recommend certain measures to help prevent or minimize adverse effects, such as appropriate, alternative day therapy; administration of proper calcium and vitamin D supplementation; or the use of other medications (i.e., H2-receptor blockers or proton pump inhibitors). In some affected individuals, certain adverse effects may necessitate a decrease in dosage or discontinuation of therapy and substitution of another appropriate treatment. However, treatment with glucocorticoids should never be abruptly stopped unless under the direct supervision of a physician.
Therapy with other immunosuppressive drugs, such as azathioprine, methotrexate, mycophenoloate mofetil, cyclophosphamide, tacrolimus, or cyclosporine, may be beneficial for some affected individuals who have an insufficient response to steroid therapy alone, dose-limiting adverse effects, or frequent relapses. For example, preliminary investigations have shown that some affected individuals may benefit from combination therapy with azathioprine and steroids, with the addition of immunosuppressant therapy often allowing the use of lower steroid doses and therefore less adverse effects from the steroid treatment. Rituximab is a monoclonal antibody directed against the CD20 protein on the surface of B cells and has shown some benefit in the treatment of dermatomyositis. In addition, reports indicate that some affected individuals have obtained benefit from methotrexate therapy for five years or more and in both muscle and skin disease. However, therapy with such immunosuppressive agents may have serious adverse effects, such as an increased susceptibility to infections and other effects. In some patients who do not improve while on glucocorticoid therapy, with or without additional immunosuppressive treatment, have been shown to benefit in the short-term from receiving monthly high-dose intravenous immunoglobulin (IVIG) for 6 months. Thus, as with steroid therapy, individuals who undergo treatment with immunosuppressive agents require ongoing monitoring to ensure appropriate response, to help minimize or manage possible side effects, and to make any necessary dosage adjustments or treatment substitutions.
Antimalarial agents, such as hydroxychloroquine, may be useful in treating the skin manifestations of the disease and allow for a lower dose of glucocorticoids; however, these patients may be at an increased risk of eruption associated with treatment. Calcium-channel blockers, mainly diltiazem, have been used in treating calcinosis in patients that develop calcium deposits.
In affected individuals with an associated malignancy, reports suggest that dermatomyositis often improves with removal of the underlying cancer*. Experts indicate that individuals with malignancy-associated dermatomyositis may also sometimes respond to therapy with glucocorticoids such as prednisone. (*Depending upon the specific form, stage, and grade of the malignancy and other factors, recommended cancer treatment may include surgical removal of the malignancy; administration of certain chemotherapy drugs; radiation therapy; and/or other measures. During radiation therapy, radiation via x-rays or other sources of radioactivity is passed through selected regions of the body to destroy cancer cells and shrink tumors.)
In some cases, physical therapy may be recommended to help improve muscle strength and avoid the development of contractures. For individuals with calcifications, physicians may sometimes recommend surgical removal of calcium deposits. Treatment for other findings potentially associated with dermatomyositis (i.e., difficulty swallowing and/or breathing; speech problems; and/or abnormalities of the heart, lungs, and/or GI tract) is symptomatic and supportive. Affected individuals should be closely monitored by physicians so that proper preventive measures may be taken to help avoid serious complications potentially associated with this disorder.
Diet and physical activity also play an important role in dermatomyositis. For example, patients with severe muscle inflammation should incorporate more protein in their diet to compensate for the loss. Patients with dysphagia may require a special diet to avoid certain foods that may exacerbate their symptoms. Additional non-pharmacological recommendations include: avoidance and/or protection from the sun; elevation of the head of the bed; not eating before bedtime; and general bed rest.
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