Dermatologic Manifestations of Dermatomyositis 

Dermatologic manifestations of dermatomyositis are only one of a set of features of this disease. Dermatomyositis is not only an idiopathic inflammatory myopathy (IIM) with characteristic cutaneous findings but also a systemic disorder that frequently affects the joints, the esophagus, the lungs, and, less commonly, the heart.^{[1, 2]}

Classification of dermatomyositis and myositis

In 1975, Bohan and Peter first suggested a set of criteria to aid in diagnosing and classifying dermatomyositis and polymyositis (PM).^[3] Of the 5 criteria, 4 relate to the muscle disease (eg, progressive proximal symmetrical weakness, elevated muscle enzyme levels, abnormal findings on electromyograms [EMGs], and abnormal findings from muscle biopsy], and the fifth is compatible cutaneous disease.

These investigators also suggested 5 subsets of myositis: (1) dermatomyositis, (2) polymyositis, (3) myositis with cancer, (4) childhood dermatomyositis/polymyositis, and (5) myositis overlapping with another collagen vascular disorder. Subsequently, Bohan and Peter noted that cutaneous disease might precede the development of the myopathy.^[4] However, another possible subset of patients with disease that affects only the skin has been recognized; this condition is known as amyopathic dermatomyositis (ADM), or dermatomyositis sine myositis. The association between dermatomyositis (and possibly polymyositis) and cancer has long been recognized.^{[5, 6, 7, 8, 9, 10]}

Rare cutaneous manifestations of dermatomyositis include vesiculobullous, erosive lesions and an exfoliative erythroderma. Biopsy samples from patients reveal an interface dermatitis similar to that of biopsy samples of heliotrope rash (see the images below), Gottron papules, poikiloderma, or scalp lesions. These cutaneous manifestations may be more common in patients with an associated malignancy than in those without a malignancy.

Amyopathic, hypomyopathic, and postmyopathic dermatomyositis

Amyopathic dermatomyositis (dermatomyositis sine myositis) is diagnosed in patients with typical cutaneous disease in whom no evidence of muscle weakness exists and in whom serum muscle enzyme levels are repeatedly normal for a 2-year period in the absence of disease-modifying therapies such as corticosteroids, immunosuppressive agents, or both. When studied, some patients with amyopathic dermatomyositis have abnormal ultrasonographic, magnetic resonance imaging (MRI) or MR spectroscopy, or muscle biopsy findings. These patients have muscle involvement, and their condition may be better classified as hypomyopathic dermatomyositis. Patients with these variations may also reflect an underlying malignancy, and some develop severe pulmonary disease, particularly persons from Asian countries.

Patients exist in whom myositis resolves following therapy but whose skin disease remains as an active, important feature of the disease. These patients are not classified as having amyopathic dermatomyositis, despite the fact that, at this point in time, the skin is the major and often only manifestation of the disease. Gerami and colleagues have suggested the term postmyopathic dermatomyositis for these patients.^[11]

Pathophysiology

The pathogenesis of the cutaneous disease of dermatomyositis is poorly understood, but it is believed that similarities exist with that of cutaneous lupus erythematosus, in which T-cells are involved and antibody-mediated cell cytotoxicity may play a role. Dermatomyositis-associated myopathy appears to be due to vascular inflammation.

See Dermatomyositis, Juvenile Dermatomyositis, and Polymyositis.

Patients with dermatomyositis often present with skin disease as one of the initial manifestations. In as many as 40% of patients, the skin disease may be the sole manifestation at the onset. Muscle disease may occur concurrently, it may precede the skin disease, or it may follow the skin disease by weeks to years. In addition, systemic manifestations may occur; therefore, a review of systems should assess for the presence of arthralgias, arthritis, dyspnea, dysphagia, arrhythmias, and dysphonia. (See Dermatomyositis.)

Several reports have also described drug-induced dermatomyositis or existing dermatomyositis exacerbated by certain drugs, including statins and interferon therapy.^[12] Dermatomyositislike skin changes have been reported with hydroxyurea in patients with chronic myelogenous leukemia or essential thrombocytosis.^{[13, 14]} Other agents that may trigger the disease include penicillamine, statin drugs, quinidine, and phenylbutazone.

Skin eruption/hair loss

Patients often notice an eruption on exposed surfaces. The disease is often pruritic, and, sometimes, intense pruritus may disturb sleep patterns. Patients may also complain of a scaly scalp or diffuse hair loss (see the image below).^[15]

Muscle involvement

Muscle involvement manifests as proximal muscle weakness. Patients often begin to note fatigue of their muscles 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 it is not a regular feature of the disease.

Malignancy

Malignancy is possible in any patient with dermatomyositis, but it is much more common in adults older than 60 years. Only a handful of children with dermatomyositis and malignancy have been reported. The history should include a thorough review of systems, as well as an assessment for previous malignancy.

Juvenile dermatomyositis

Children with dermatomyositis may have an insidious onset that hides the true diagnosis until the dermatologic disease is clearly observed and diagnosed. Calcinosis is a complication of juvenile dermatomyositis (see the following image), but it is rarely observed at the onset of disease. Black persons and patients in lower socioeconomic groups are more likely to have a delay in their diagnosis. The prognosis in children with dermatomyositis is worse in those in whom diagnosis is delayed. (See Juvenile Dermatomyositis.)

Dermatomyositis is a disease that primarily affects the skin and the muscles, but it might also affect other organ systems.

The characteristic and possibly pathognomonic cutaneous features of dermatomyositis are the heliotrope rash and Gottron papules. Several other cutaneous features are characteristic of the disease despite not being pathognomonic. They include malar erythema, poikiloderma in a photosensitive distribution, violaceous erythema on the extensor surfaces, and periungual and cuticular changes.

Heliotrope rash and Gottron papules

The heliotrope rash consists of a violaceous to dusky erythematous rash with or without edema in a symmetrical distribution involving the periorbital skin (see the image below). Sometimes, this sign is subtle and may consist of only a mild discoloration along the eyelid margin. Similar to other areas, scales may be present on the eyelids. A heliotrope rash is rarely observed in other disorders; therefore, its presence is highly suggestive of dermatomyositis.

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

Nail fold changes consist of periungual telangiectases and/or a characteristic cuticular change with hypertrophy of the cuticle and small, hemorrhagic infarcts in this hypertrophic area (also seen in the image below). Periungual telangiectases may be clinically apparent, or they may be appreciated only by capillary microscopy.

Poikiloderma and photodistribution

Poikiloderma may occur on exposed skin, such as the extensor surfaces of the arm, the vee of the neck (see the image below), or the upper part of the back (Shawl sign) or on the lateral thighs (Holster sign).

With the exception of the heliotrope rash, the eruption of dermatomyositis is photodistributed and photoexacerbated (see the following image). Patients rarely complain of photosensitivity, despite the prominent photodistribution of the rash.

Face, scalp, and knuckle involvement

Facial erythema may also occur in dermatomyositis. This change must be differentiated from lupus erythematosus, rosacea, seborrheic dermatitis, or atopic dermatitis. A study from Japan highlighted the finding of disease on the face that mimicked seborrhea.^[16]

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. In some patients, nonscarring alopecia may occur and often follows a flare of systemic disease.

In some patients, particularly those with antisynthetase antibodies, ulceration over the knuckles occurs (see the image below). These lesions may require surgical intervention.

Other cutaneous findings

Other cutaneous lesions have been described in patients with dermatomyositis or polymyositis that do not reflect the interface changes observed at histopathologic examination with pathognomonic or characteristic lesions. These include panniculitis (see the following image) and urticaria, as well as changes of hyperkeratosis of the palms known as mechanic's hands. Other findings include cutaneous mucinosis, follicular hyperkeratosis, hyperpigmentation, ichthyosis, white plaques on the buccal mucosa, cutaneous vasculitis, and a flagellate erythema.

Calcinosis of the skin or the muscle is unusual in adults, but it may occur in as many as 40% of children or adolescents with dermatomyositis. Calcinosis cutis manifests as firm, yellow or flesh-colored nodules, often over bony prominences. Occasionally, these nodules can extrude through the surface of the skin, in which case, secondary infection may occur.^[17]

Muscular and systemic findings

As noted in Clinical Presentation, muscle disease may occur concurrently with, precede, or follow the skin disease by weeks to years. Proximal symmetrical muscle weakness may be found. Patients may have difficulty rising from a chair or squatting and then raising themselves from this position. Sometimes, in an effort to rise, 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 flexor muscles. Distal strength is almost always maintained. Muscle tenderness is a variable finding.

Other systemic features include joint swelling, changes associated with Raynaud phenomenon, and abnormal findings on cardiopulmonary examination. Joint swelling occurs in some patients with dermatomyositis. The small joints of the hands are the most frequently involved. The arthritis associated with dermatomyositis is nondeforming. Patients with pulmonary disease may have abnormal breath sounds. Patients with an associated malignancy may have physical findings relevant to the affected organs.

Skin biopsy samples reveal an interface dermatitis that is difficult to differentiate from lupus erythematosus. Often, the histologic features of dermatomyositis and lupus erythematosus are identical. Both may contain excessive mucin, and both demonstrate an interface vacuolar dermatitis. Well-formed lesions of discoid lupus erythematosus differ from those of dermatomyositis, but often dermatomyositis and subacute cutaneous lupus erythematosus cannot be differentiated.^[18]

The therapy for dermatomyositis involves general measures, measures to control the muscle disease, and measures to control the skin disease. In addition, in some patients, treating other systemic manifestations or complications may be necessary. (See Dermatomyositis.)

Whereas therapy of the muscle component involves the use of corticosteroids with or without an immunosuppressive agent, therapy for the cutaneous disease is often difficult. Patients who present primarily with skin disease (amyopathic dermatomyositis) and those in whom the muscle component is controlled but who still have significant skin disease exist. The first-line of therapy is recognizing that the patient is photosensitive and advising the patient to avoid sun exposure and to use sun protective measures, including broad-spectrum sunscreens. Topical corticosteroids have also been used.

Hydroxychloroquine and chloroquine have been beneficial in small open-label case studies.^{[19, 20]} Methotrexate is also useful,^{[21, 22]} and mycophenolate mofetil has been reported to be useful.^{[23, 24]} In addition, intravenous immune globulin not only benefited the muscle but also cleared the skin lesions in the patients in whom it was used.^[25] Rituximab has been used for skin disease, but the results are mixed.^[26]

Aggressive early treatment of the myositis, particularly in children, may aid in the prevention of calcinosis. Once established, the process is debilitating in many patients. Although spontaneous remission is possible, it often occurs after many years. The use of the calcium channel blocker diltiazem (240 mg BID) is reportedly associated with gradual resolution of calcinosis in a small number of cases.^[27] In addition, the use of an oral bisphosphonate might be helpful.^[28] Intravenous pamidronate has also been demonstrated in several cases to result in resolution of the calcinosis.^[29] Some patients with local areas of calcinosis may wish to have them surgically removed, although surgical intervention is usually not necessary.

Sun protective measures are necessary for patients with skin disease.

Monitoring of the dermatomyositis disease activity is necessary on at least a monthly basis. An assessment of the skin disease is by a physical examination in conjunction with a history. A relatively new validated measure, known as the Cutaneous Dermatomyositis Area and Severity Index (C-DASI), for assessing skin disease might be useful, particularly when performing clinical studies in the future.^[30]

Annual physical examinations are useful to monitor for potential toxicity from therapy or for a malignancy. Malignancy evaluations should be conducted for at least the first 3 years following diagnosis of dermatomyositis and at other times if symptoms develop or the patient's disease is poorly responsive to therapy. After 3 years, patients should be monitored as any other person of the same age, race, and sex. Women should be screened for ovarian cancer.^[31]