Dermatomyositis is an idiopathic inflammatory myopathy that most frequently affects the skin and muscles, but may also affect the joints, the esophagus, the lungs and, less commonly, the heart.
An association between dermatomyositis and cancer has long been recognized in adult patients.
Dermatomyositis may spontaneously remit in as many as 20% of affected patients. About 5% of patients have a fulminant progressive course with eventual death. It can occur in people of any age. Two peak ages of onset [5-10 years and 50 years exist] and the condition is more common in females.
Pathophysiology of Dermatomyositis
The disease is considered to be the result of a humoral attack against the muscle capillaries and small arterioles an ongoing microangiopathy.
Capillary destruction lead to microinfarction of the muscles and perifascicular atrophynecrosis and muscle degeneration.
The pathogenesis of the skin component is poorly understood, but is thought to be similar to that of muscle involvement.
Two subset of patients with dermatomyositis are known.
Also called dermatomyositis sine myositis affect only skin and normal serum muscle enzyme levels. However some of them may have abnormal findings on ultrasonography, electromyography, magnetic resonance imaging (MRI), magnetic resonance spectroscopy, or muscle biopsy and are better classified as hypomyopathic dermatomyositis. ADM or hypomyopathic DM may also be related to an underlying malignancy.
The term clinically amyopathic dermatomyositis is often used to encompass patients with both amyopathic and hypomyopathic dermatomyositis
Aother subset of patients with dermatomyositis with controlled myopathy who continue to have severe and sometimes debilitating skin disease (ie, postmyopathic dermatomyositis).
Causes of Dermatomyositis
The cause of dermatomyositis is unknown. However, genetic, immunologic, infectious, and environmental factors have been implicated.
Possible triggers of include
- Human T-cell lymphotropic virus type 1 [HTLV-1]
- Toxoplasma species
- Borrelia species
- Anti–tumor necrosis factor drugs
- Bacillus Calmette-Guérin (BCG) vaccine
Clinical Presentation of Dermatomyositis
Patients often present with skin disease, and is sole sole manifestation at onset. Muscle disease may occur concurrently, may precede the skin disease, or may follow the skin disease by weeks to years.
Typically proximal muscles are involved and patients complain of muscle fatigue or weakness when climbing stairs, walking, rising from a sitting position, combing their hair, or reaching overhead.
Arthralgia, arthritis, dyspnea, dysphagia, arrhythmia, and dysphonia can be reported.
Children resembles the adult form of the disease and commonly develop a tiptoe gait secondary to flexion contracture of the
Extramuscular manifestations are more common in children and include
- Systemic disturbances such as fever, arthralgia, malaise, weight loss, Raynaud phenomenon
- Gastroesophageal reflux
- Atrioventricular defects, tachyarrhythmias, dilated cardiomyopathies
- GI ulcers and infections
- Joint contractures
- Pulmonary involvement [Thoracic muscles weakness, interstitial lung disease]
Subcutaneous calcifications are higher in children.
A detailed drug history is warranted to rule out drug induced cases.
A thorough history, review of systems, and assessment for previous malignancy should be performed in all patients with dermatomyositis due to association with malignancies especially in persons older than 60 years of age.
Other skin features are
- Poikiloderma – Erythema, hypopigmentation, hyperpigmentation, and telangiectasias, may occur on photoexposed skin, .
- Pruritic eruption on photoexposed surfaces.
- Dilated capillary loops at the base of the fingernail, cuticular hypertrophy and ragged cuticles.
- Palmar and lateral surfaces of the fingers may become rough and cracked [Mechanic’s hands]
Other rare skin findings include the following:
- Cutaneous mucinosis
- Follicular hyperkeratosis
- White plaques on the buccal mucosa
- Cutaneous vasculitis
- Flagellate erythema
- Diffuse subcutaneous edema
- Vesiculobullous or erosive lesions
- Exfoliative erythroderma
There would be weakness of muscles, often proximal and often symmetrical.
The degree of weakness may range from mild to moderate to severe. Sometimes, quadriparesis is present.
Muscle tenderness may be especially early in the course of the disease; muscle tenderness is a variable finding. Sensation is normal, and tendon reflexes are preserved unless the muscle is severely weak and atrophic.
Other systemic features include joint swelling, changes associated with Raynaud phenomenon, and abnormal findings on cardiopulmonary examination.
- Discoid Lupus Erythematosus
- Pityriasis Rubra Pilaris
- Polymorphous Light Eruption
- Systemic Lupus Erythematosus
- Subacute Cutaneous Lupus Erythematosus
- Graft Versus Host Disease
- Lichen Myxedematosus
- Lichen Planus
- Multicentric Reticulohistiocytosis
Muscle enzyme levels
Abnormally raised during the course of dermatomyositis
- Creatine kinase (CK)
- AST and/or LDH [Aspartate aminotransferase [AST] and/or lactic dehydrogenase [LDH])
- Myositis-specific antibodies
- Antinuclear antibodies
- Anti–Mi-2 antibodies
- Asssociated with pulmonary involvement (interstitial lung disease), Raynaud phenomenon, arthritis, and mechanic’s hands in the setting of the anti-synthetase syndrome.
MRI can assess the presence of an inflammatory myopathy, even in patients without weakness.
Electromyography can detect muscle inflammation and damage but the use has decreased after advent of MRI.
Evaluation of esophageal dysmotility.
scanning of the chest, abdomen, and pelvis for evaluation of potential malignancy that might be associated with dermatomyositis.
For malignancy screening in women.
To rule out breast malignancy.
- Pulmonary function studies with diffusion capacity
- Electrocardiography (ECG)
- Esophageal manometry (in selected patients)
- Malignancy screening tests
- Age-related colonoscopy
- Fecal-occult blood testing for malignancy screening
- Pap Smear
- Cancer antigen 125 (CA-125) and CA-19-9 for malignancy screening
Muscle biopsy, either open or via needle, may enhance the clinician’s ability to diagnose dermatomyositis. The biopsy results may be useful in differentiating steroid myopathy from active inflammatory myopathy when patients have been on corticosteroid therapy but are still weak.
- Perivascular and interfascicular inflammatory infiltrates
- Muscle fiber degeneration/regeneration
Non-pharmacological Measures for Dermatomyositis
- Bed rest – for those with severe inflammation of the muscles.
- Physical therapy to prevent the contractures that can complicate the disease when patients do not fully move their joints.
- Elevation of the head of their bed and avoidance of eating prior to bedtime for patients with dysphagia and/or gastroesophageal reflux
- Diet with extra proteins
- Sun avoidance and sun protection
- Resistance training and aerobic exercise
Drug Treatment for Dermatomyositis
Steroid Sparing Drugs
Classicially steroids like prednisone were first line of treatment but few drugs are able to limit or avoid steroid use and are immunosuppressives called steroid sparing drugs.
These drugs are
- Steroid-sparing immunosuppressive or cytotoxic agent
- Mycophenolate mofetil
Generally, methotrexate, mycophenolate mofetil, or azathioprine are used as first line.
Use of monthly high-dose intravenous immune globulin for six months is considered in refractory cases.
Tacrolimus is another promising drug in trial stage for dermatomyositis.
Methotrexate and mycophenolate mofetil and intravenous immunoglobulin are effective in skin lesions too.
Subcutaneous IgG is also given for skin lesions.
The use of the calcium channel blocker diltiazem, intravenous pamidronate has been effective in resolution of the calcinosis.
Some patients with localized areas of calcinosis may wish to have the calcinotic nodules surgically removed, particularly if they are tender
Risk factors for a poorer prognosis in patients with dermatomyositis include the following:
- An associated malignancy
- Cardiac, pulmonary, or esophageal involvement
- Older age (>60 years)
Dermatomyositis may cause death because of muscle weakness or cardiopulmonary involvement. Patients with an associated cancer may die of the malignancy.
Contractures can occur if the patient is immobile.
Dermatomyositis may may increase risk for venous thromboembolism (deep venous thrombosis or pulmonary embolism) and myocardial infarction.
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