Dermatomyositis

Original Editors Megan Sarason from Bellarmine University's Pathophysiology of Complex Patient Problems project.

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Definition/Description

A systemic connective tissue disease, found in the rheumatoid family, characterized by inflammatory and degenerative changes in the muscles and skin leading to symmetric weakness and some degree of muscle atrophy, principally in the limb girdles, neck and pharynx.  This disease has also shown to effect the esophagus, lungs, and least commonly the heart.

Prevalence

• In the United States, approximately 5-10 in 1 million people are affected and the incidence appears to be increasing.
• May appear at any age but most commonly from age 40-60 in adulthood; in childhood 5-15
• The female to male ratio is 2:1
  

Characteristics/Clinical Presentation

• Symptom onset maybe acute or insidious
•  Progressive symmetric muscle weakness primarily in muscles of proximal joints and neck and pharynx
•  Dusky or erythematous skin rash, potentially scaly, elevated, or smooth. Typically found on the face resembling the butterfly rash associated with SLE, neck, shoulders, chest and back, forearms, lower legs, medial malleoli, and dorsum of the proximal interphalangeal and metacarpophalangeal joints.

• Gottron's papules 

•  Base and sides of nails maybe hyperemic
•  Muscular pain and tenderness typically associated with the rash
•  Subcutaneous calcifications may occur particularly in childhood
• diffuse alopecia with scaly scalp
  
•  Fatigue, fever, weight loss
•  Difficulty swallowing
•  Cardiopulmonary involvement such as arrhythmias, congestive heart failure, conduction deficits, ventricular hypertrophy, or pericarditis and respiratory muscles in severe cases 
  

Subtypes 

JUVENILE DERMATOMYOSITIS
While the clinical presentation of juvenile dermatomyositis is usually different from the presentation of the adult type, the skin lesions are similar, with the exception of an increased incidence of calcinosis cutis in juvenile patients. Common findings include low-grade fever, increased risk of gastrointestinal manifestations, and symmetric arthritis of the large and small joints. Asymptomatic cardiac conduction delays or right bundle branch block may be found in 50 percent of this group.

Patients may exhibit weakness of the truncal muscles that requires them to use their arms to push themselves up from a prone position (i.e., Gower's sign). There does not appear to be any association between juvenile dermatomyositis and malignancy.

OVERLAP SYNDROME
A number of patients with dermatomyositis also meet the criteria for one of the connective tissue disorders. To be a true overlap syndrome, the patient must meet the diagnostic criteria for each separate disorder. Overlap syndrome occurs more frequently in females than in males, with a 9:1 ratio. Eleven to 40 percent of patients with dermatomyositis have been reported to have a concomitant diagnosis of a connective tissue disorder.

These disorders include rheumatoid arthritis, scleroderma, systemic lupus erythematosus, Sjögren's syndrome, polyarteritis nodosa and mixed connective tissue disease', and these patients may present withp'olyarthritis, sicca syndrome, sclerodactyly, Raynaud's phenomenon and late symptoms of myositis. Patients are also more likely to have positive nonmyositis–associated antibodies (such as double-stranded DNA, antinuclear antibodies [ANA], Scl-70, Jo-1 precipitating antibodies, PM-Scl, Ku antibodies or extractable nuclear antigen antibodies). ANA are found in up to 80 percent of patients with dermatomyositis or polymyositis, but this finding does not aid in distinguishing myositis from scleroderma or other rheumatologic diseases. Precipitating autoantibodies to the Mi-2 antigen are specific for dermatomyositis but are found in only about 20 percent of patients with dermatomyositis. In patients with overlap syndrome, the myositis tends to respond better to treatment with corticosteroids than it does in patients with an idiopathic etiology.

AMYOPATHIC DERMATOMYOSITIS
This classification has been controversial because it does not strictly meet the criteria put forth by Bohen and Peter.Amyopathic patients essentially have pathognomonic skin changes without clinical or laboratory evidence of muscle involvement. This condition has been reported in approximately 2 to 11 percent of patients with dermatomyositis. Patients most commonly present with lethargy, pruritus, fatigue, photosensitivity or arthralgias. In some cases, myositis developed later; in others, myositis that was not found by standard methods was suspected on the basis of magnetic resonance imaging (MRI).

DERMATOMYOSITIS/MALIGNANCY
Although an increased risk of malignancy has not been associated with juvenile dermatomyositis, it has been demonstrated in adults with dermatomyositis. This risk appears to be highest in patients diagnosed with dermatomyositis after 45 years of age. The most commonly reported malignancies are ovarian and gastric cancer, and lymphoma. Other reported malignancies include lung, male genital organ, nonmelanoma skin, Kaposi's sarcoma, mycosis fungoides and melanoma.

Skin changes are not different in patients with or without malignancy. Therefore, careful investigation for malignancy should be initiated at the time dermatomyositis is diagnosed. In women with dermatomyositis, there is a significant association with ovarian cancer, and some authors recommend that the work-up for dermatomyositis include a comprehensive gynecologic evaluation, including a cancer antigen (CA-125) baseline screen, mammography and transvaginal ultrasonographic evaluation of the ovaries at baseline, and gynecologic examinations at six- to 12-month intervals for at least two years.

Medications

Corticosteroids:

• Prednisone

Immunosuppressive or cytotoxic agent: 

• Methotrexate
• Azathioprine
• Cyclophosphamide
• Cyclosporin
• Mycophenolate mofetil
• Chlorambucil

Antimalarial: steroid-sparing agent to treat skin disease

• Hydroxychloroquine and chloroquine

Mainstay adequate antibody levels to improved muscle function and for skin lesions in patients whom corticosteroids and immunosupressives have failed:

• Intravenous immune globulin

Monoclonal antibodies (destruction of B cells):

• Rituximab

Calcium channel blocker: (gradual resolution of calcinosis)

• Diltiazem

Diagnostic Tests/Lab Tests/Lab Values

laboratory studies are helpful but nonspecific:

•  ESR frequently elevated
•  Antinuclear antibodies (ANA) elevated in 60 to 80 percent of patients
•  Elevated creatine kinase (CK) enzyme, transaminases, and lactate dehyrogenase levels
•  EMG to measure the electrical activity of the muscles: typically present as short-wave and fibrillations or myopathic pattern, 10 percent are false-negative
• Rheumatoid factor: elevated in 20 percent of patients, most often in those with overlap syndromes
• Neopterin and factor VIII–related antigen (von Willebrand factor): reported to correlate with juvenile DM
  

Causes

• The etiology of this disease is unknown
• Potential autoimmune mechanism; T cells inappropriately recognize muscle fiber antigens as foreign and attack the    muscle tissues causing muscle breakdown
• Potentially triggered by a virus
• Potentially drug induced
  

Systemic Involvement

Systemic manifestations:
Common: proximal muscle weakness, dysphonia, dysphagia
Less common: respiratory muscle weakness, visual changes, abdominal pain

Systemic complications/association:

Cardiomyopathy
Cardiac conduction defects

Aspiration pneumonia secondary to respiratory muscle weakness
Diffuse interstitial pneumonitis/fibrosis
Large-bowel infarction secondary to vasculopathy has occurred in juvenile patients with myositis
Muscle atrophy
Muscle calcification
Ocular complications including iritis, nystagmus, cotton-wool spots, optic atrophy, conjunctival edema and pseudopolyposis
Internal malignancy

Medical Management (current best evidence)

 The main goals when treating patients with dermatomyositis are improve function and prevent disability. The treatment regimen must be instituted early and requires a team approach between the physical therapist, dermatologist and family physician.  While currently there is no cure for this systemic disease the symptoms can be treated.  Corticosteroids are used initially to reduce the inflammation, shorten the time to normalization of muscle enzymes, and reduce morbidity. Maintenance therapy with Prednisone usually is necessary indefinitely in the adult patient. Immunosuppressive therapies may be used in individuals who do not respond well to the corticosteroids.  The skin disease is primarily treated with sun avoidance, topical corticosteroids, antimalarial agents,methotrexate, mycophenolate mofetil, and/or intravenous immune globulin.  Patient education is highly important to assist in control of the disease process.

Physical Therapy Management (current best evidence)

Preferred Practice Patterns for Physical Therapy:

• Impaired Joint Mobility, Motor Function, Muscle Performance, and Range of Motion Associated with Connective Tissue Dysfunction.
• Impairments/ Skin Involvement Into Fascia, Muscle, or Bone and Scar Formation

Focus of Treatment should include:  Patient education on joint preservation

• Strengthening to prevent atrophy once inflammation is controlled
• Range of motion exercises to prevent contractures
• Passive stretching and splinting
  

Alternative/Holistic Management (current best evidence)

Stress management:  

• Meditation
• Yoga

Diet Changes:

• diet high in fiber (if large amount of muscle damage has occurred)
• low-fat

Avoidance of sun and increased use of sunscreen has shown to decrease skin symptoms.

Differential Diagnosis

• CREST Syndrome
• Parapsoriasis
• Graft Versus Host Disease
• Pityriasis Rubra Pilaris
• Lichen Myxedematosus
• Polymorphous Light Eruption
• Lichen Planus
• Psoriasis, Plaque
• Lupus Erythematosus, Acute
• Rosacea
• Lupus Erythematosus, Discoid
• Sarcoidosis
• Lupus Erythematosus, Subacute Cutaneous
• Tinea Corporis
• Morphea
• Urticaria, Chronic
• Multicentric Reticulohistiocytosis
  

Case Reports

http://www.intarchmed.com/content/1/1/25

http://pathhsw5m54.ucsf.edu/case34/case34.html

http://www.amc.edu/amr/archives/200201/case02.html

Resources

Support Groups:

Polymyositis and Dermatomyositis support group

Myositis support group

General Information:

Myositis

dermatomyositis

Recent Related Research (from Pubmed)

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