eMedicine Specialties > Rheumatology > Systemic Rheumatic Disease

Dermatomyositis

Author: Jeffrey P Callen, MD, Professor of Medicine, Chief, Division of Dermatology, University of Louisville School of Medicine
Contributor Information and Disclosures

Updated: Apr 14, 2009

Introduction

Background

Dermatomyositis (DM) is an idiopathic inflammatory myopathy (IIM) with characteristic cutaneous findings. In 1975, Bohan and Peter first suggested a set of criteria to aid in the diagnosis and classification of dermatomyositis and polymyositis (PM).^1,2 Four of the 5 criteria are related to the muscle disease, as follows: progressive proximal symmetrical weakness, elevated levels of muscle enzymes, an abnormal finding on electromyography, and an abnormal finding on muscle biopsy. The fifth criterion was compatible with cutaneous disease.

The association between dermatomyositis (and possibly polymyositis) and malignancy has been recognized for a long time. Dermatomyositis is a systemic disorder that frequently affects the esophagus and lungs and, less commonly, the heart. Calcinosis is a complication of dermatomyositis that is observed most often in children and adolescents.

Therapy of the muscle component involves the use of corticosteroids with or without an immunosuppressive agent. The skin disease is treated with sun avoidance, sunscreens, topical corticosteroids, antimalarial agents, methotrexate, mycophenolate mofetil, and/or intravenous immune globulin. Rituximab may prove useful in the treatment of muscle disease of dermatomyositis and has had mixed results in treatment of skin disease.^3,4 Recently, efalizumab has been reported to be useful for skin disease.

Efalizumab (Raptiva), a drug indicated for psoriasis, is being withdrawn from the US market and will no longer be available after June 8, 2009, because of potential risk for progressive multifocal leukoencephalopathy (PML). PML is a rapidly progressive infection of the central nervous system caused by the JC virus that leads to death or severe disability. Demyelination associated with PML is a result from the JC virus infection. JC virus belongs to the genus Polyomavirus of the Papovaviridae. PML should be considered in any patient who presents with newly onset neurologic manifestations and who has taken efalizumab. For more information, see the Food and Drug Administration MedWatch Safety Alert.

The prognosis of dermatomyositis depends on the severity of the myopathy, the presence of malignancy, and/or the presence of cardiopulmonary involvement. Residual weakness is common, even in patients who fully recover.

For additional information on skin disease of dermatomyositis, see the eMedicine article Dermatomyositis in the Dermatology volume.

Pathophysiology

The pathogenesis of the cutaneous disease of dermatomyositis is poorly understood. Bohan and Peter (1975) suggested 5 subsets of myositis, as follows: dermatomyositis, polymyositis, myositis with malignancy, childhood dermatomyositis/polymyositis, and myositis overlapping with another collagen-vascular disorder. In a subsequent publication, Bohan et al (1975) noted that cutaneous disease may precede the development of the myopathy. The existence of another subset of patients with dermatomyositis that affects only the skin (called amyopathic dermatomyositis [ADM] or dermatomyositis-sine myositis) was only recently recognized. Lastly, another subset of patients with dermatomyositis have controlled myopathy but continue to have severe and sometimes debilitating skin disease; this condition has been termed postmyopathic dermatomyositis.

Recent studies of the pathogenesis of the myopathy have been controversial. Some suggest that the myopathy in dermatomyositis and polymyositis is pathogenetically different. Dermatomyositis is probably caused by complement-mediated (terminal attack complex) vascular inflammation, while polymyositis is caused by the direct cytotoxic effect of CD8⁺ lymphocytes on muscle. However, other studies of cytokines suggest that some of the inflammatory processes may be similar. A recent report has linked tumor necrosis factor (TNF) abnormalities with dermatomyositis.⁵

Frequency

United States

The incidence of dermatomyositis/polymyositis has been estimated at 5.5 cases per million people, and the incidence is apparently increasing.

Mortality/Morbidity

• Dermatomyositis may cause death because of muscle weakness or cardiopulmonary involvement. Patients with an associated malignancy may die of the malignancy.
• Most patients with dermatomyositis survive, in which case they may develop residual weakness and disability. Children with severe dermatomyositis may develop contractures.
• Calcinosis may complicate dermatomyositis. It is very rare in adults but is more common in children and has been linked to delay in diagnosis and to less-aggressive therapy.

Race

Dermatomyositis and polymyositis have no racial predilection.

Sex

Dermatomyositis and polymyositis are twice as common in women as in men.

Age

Dermatomyositis can occur in people of any age. Two peak ages of onset exist. In adults, the peak age of onset is approximately 50 years, and, in children, the peak age is approximately 5-10 years.

Clinical

History

• Persons with dermatomyositis (DM) often present with skin disease as one of the initial manifestations. In perhaps as many as 40% of individuals with dermatomyositis, the skin disease is the sole manifestation at onset. Muscle disease may occur concurrently, may precede the skin disease, or may follow the skin disease by weeks to years.
• Individuals with dermatomyositis often notice an eruption on exposed surfaces. The rash is often pruritic, and intense pruritus may disturb sleep patterns. Patients may also report a scaly scalp or diffuse hair loss.
• Muscle involvement manifests as proximal muscle weakness. Affected patients often begin to note muscle fatigue or weakness when climbing stairs, walking, rising from a sitting position, combing their hair, or reaching for items in cabinets that are above their shoulders. Muscle tenderness may occur but is not a regular feature of dermatomyositis.
• Systemic manifestations may occur; therefore, the review of systems should assess for the presence of arthralgia, arthritis, dyspnea, dysphagia, arrhythmia, and dysphonia.
• Malignancy is possible in any patient with dermatomyositis but is more common in adults older than 60 years. Only a few children with dermatomyositis and malignancy have been reported. The history should include a thorough review of systems and an assessment for previous malignancy.
• Children with dermatomyositis may have an insidious onset that defies diagnosis until the dermatologic disease is clearly observed and diagnosed. Calcinosis is a complication of juvenile dermatomyositis but is rarely observed at disease onset. Ask questions about hard nodules of the skin during the initial examination.

Physical

• Dermatomyositis is a disease that primarily affects the skin and the muscles but may affect other organ systems.
• The characteristic, and possibly pathognomonic, cutaneous features of dermatomyositis include heliotrope rash and Gottron papules. Several other cutaneous features, including malar erythema, poikiloderma (ie, variegated telangiectasia, hyperpigmentation) in a photosensitive distribution, violaceous erythema on the extensor surfaces, and periungual and cuticular changes, are characteristic of dermatomyositis even though they are not pathognomonic.
• Muscle findings associated with dermatomyositis typically include proximal weakness and, sometimes, tenderness. Other systemic features include joint swelling, changes associated with Raynaud phenomenon, and abnormal cardiopulmonary examination findings.
• The heliotrope rash consists of a violaceous-to-dusky erythematous rash with or without edema in a symmetrical distribution involving periorbital skin. Sometimes, this sign is subtle and may involve only a mild discoloration along the eyelid margin. A heliotrope rash is rarely observed in other disorders; thus, its presence strongly suggests dermatomyositis.
  
  

  

  The heliotrope flower from which the manifestation of dermatomyositis is named.

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  The heliotrope flower from which the manifestation of dermatomyositis is named.

  
  

  

  Heliotrope rash in a woman with dermatomyositis.

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  Heliotrope rash in a woman with dermatomyositis.

• The Gottron papules are found over bony prominences, particularly the metacarpophalangeal joints, the proximal interphalangeal joints, and/or the distal interphalangeal joints. Papules may also be found overlying the elbows, knees, and/or feet. The lesions consist of slightly elevated violaceous papules and plaques. A slight scale and, occasionally, a thick psoriasiform scale may be present. These lesions may resemble lesions of lupus erythematosus (LE), psoriasis, or lichen planus (LP).
  
  

  

  Gottron papules and nailfold telangiectasia are present in this patient with dermatomyositis.

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  Gottron papules and nailfold telangiectasia are present in this patient with dermatomyositis.

• Nailfold changes consist of periungual telangiectases and/or a characteristic cuticular change with hypertrophy of the cuticle and small hemorrhagic infarcts with this hypertrophic area. Periungual telangiectases may be apparent clinically or may be visible only on capillary microscopy.
• Poikiloderma may occur on exposed skin, such as the extensor surfaces of the arm, and may appear in a V-shaped distribution over the anterior neck and upper chest and back (ie, shawl sign).
  
  

  

  Dermatomyositis is often associated with a poikiloderma in a photodistribution.

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  Dermatomyositis is often associated with a poikiloderma in a photodistribution.

• With the exception of the heliotrope rash, the eruption of dermatomyositis is photodistributed and photoexacerbated. Despite the prominent photodistribution of the rash, patients rarely report photosensitivity.
  
  

  

  These lesions on the dorsal hands demonstrate the photodistribution of dermatomyositis. Note the sparing of the interdigital web spaces.

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  These lesions on the dorsal hands demonstrate the photodistribution of dermatomyositis. Note the sparing of the interdigital web spaces.

• Facial erythema may also occur in dermatomyositis. This change must be differentiated from LE, rosacea, seborrheic dermatitis, and atopic dermatitis.
• Scalp involvement in dermatomyositis is relatively common and manifests as an erythematous-to-violaceous psoriasiform dermatitis. Clinical distinction from seborrheic dermatitis or psoriasis is occasionally difficult. Nonscarring alopecia may occur in some patients and often follows a flare of systemic disease.
  
  

  

  A diffuse alopecia with a scaly scalp dermatosis is common in patients with dermatomyositis.

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  A diffuse alopecia with a scaly scalp dermatosis is common in patients with dermatomyositis.

• Dermatomyositis-sine myositis, also known as amyopathic dermatomyositis (ADM), is characterized by typical cutaneous disease, no clinical evidence of muscle weakness, and normal serum muscle enzyme levels for at least 2 years. Patients who have undergone disease-modifying therapies such as corticosteroid or immunosuppressive agent treatment are not classified as having ADM. Some patients with ADM have abnormal findings on ultrasonography, MRI, or muscle biopsy. These patients have subclinical muscle involvement, but their condition may still be classified as ADM. Because many patients with ADM are not evaluated beyond clinical and enzymatic studies, many believe that ADM represents a systemic process that requires systemic therapies.
• Some cases of myositis resolve following therapy, but the skin disease remains an active important feature of dermatomyositis. Although the skin disease is the major, and often only, manifestation of dermatomyositis, these patients are not diagnosed with ADM. In addition, a small subset of patients never develop myositis despite having prominent cutaneous changes. Rare cutaneous manifestations of dermatomyositis include vesiculobullous erosive lesions and exfoliative erythroderma. Biopsy tissue samples from these patients reveal an interface dermatitis (ie, inflammation at the dermal-epidermal junction) similar to biopsy tissue samples from heliotrope rash, Gottron papules, poikiloderma, or scalp lesions. These cutaneous manifestations may be more common in patients with an associated malignancy.
• Various other cutaneous lesions that do not reflect the interface changes observed histopathologically with the pathognomonic or characteristic lesions have been described in patients with dermatomyositis or polymyositis. Panniculitis, urticaria, and hyperkeratosis of the palms (known as mechanic's hands) are examples of these cutaneous lesions. Other findings include cutaneous mucinosis, follicular hyperkeratosis, hyperpigmentation, ichthyosis, white plaques on the buccal mucosa, cutaneous vasculitis, and flagellate erythema.
• Muscle disease of dermatomyositis manifests as proximal symmetrical muscle weakness. Affected patients may have difficulty rising from a chair or squatting and raising themselves from this position. In an effort to rise, some patients use other muscles that are not as affected. The careful examiner may note this finding. Testing of the muscle strength is part of each assessment of the patient. Often, the extensor muscles of the arms are more affected than the flexors. Distal strength is almost always maintained. Muscle tenderness is a variable finding.
• Calcinosis of the skin or muscle is unusual in adults with dermatomyositis but may occur in as many as 40% of children or adolescents with the disease. Calcinosis cutis manifests as firm, yellow- or flesh-colored nodules, often over bony prominences. Occasionally, the nodules extrude through the surface of the skin, in which case secondary infection may occur.
  
  

  

  Calcinosis caused by dermatomyositis (DM) in childhood can be observed in a patient who had active DM 15 years before the time of this photograph.

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  Calcinosis caused by dermatomyositis (DM) in childhood can be observed in a patient who had active DM 15 years before the time of this photograph.

• Joint swelling occurs in some patients with dermatomyositis. The small joints of the hands are most frequently involved. The arthritis associated with dermatomyositis is not erosive or deforming.
• Patients with pulmonary disease may have abnormal breath sounds (crackles from interstitial fibrosis or pneumonitis).
• Patients with an associated malignancy may have physical findings relevant to the affected organs.

Causes

The cause of dermatomyositis is unknown; however, the following factors have been implicated:

• A genetic component may predispose to dermatomyositis. Dermatomyositis rarely occurs in multiple family members but may be linked to certain human leukocyte antigen (HLA) types (eg, DR3, DR5, DR7). In addition, polymorphisms of TNF-alpha have been linked to photosensitivity in patients with dermatomyositis.
• Immunological abnormalities are common in patients with dermatomyositis. Patients frequently have circulating autoantibodies. Abnormal T-cell activity may be involved in the pathogenesis of both the skin and the muscle disease. In addition, family members may have other diseases associated with autoimmunity.
• Autoantibodies to nuclear antigens (ANA) and cytoplasmic (ie, antitransfer RNA synthetases) antigens may be present. Although their presence may help to define subtypes of dermatomyositis and polymyositis, their role in pathogenesis is uncertain.
• Infectious agents, including viruses (eg, coxsackievirus, parvovirus, echovirus, human T-cell lymphotrophic virus type 1 [HTLV-1], HIV) and Toxoplasma and Borrelia species, have been suggested as possible triggers of dermatomyositis.
• Several cases of drug-induced dermatomyositis have been reported. Dermatomyositislike skin changes have been reported with hydroxyurea in patients with chronic myelogenous leukemia or essential thrombocytosis. Other agents that may trigger the disease include penicillamine, statin drugs, quinidine, and phenylbutazone.
• Dermatomyositis may be initiated or exacerbated by silicone breast implants or collagen injections, but the evidence for this is anecdotal and has not been verified in case-control studies. A recent report detailed HLA differences among women in whom inflammatory myopathy develops after they received silicone implants.⁶

• Search for CME/CE on This Topic »

• Dermatomyositis/Polymyositis (Neurology)
• Dermatomyositis (Dermatology)
• Juvenile Dermatomyositis (Pediatrics: General Medicine)
• Mixed Connective Tissue Disease (Dermatology)

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