Dermatomyositis (DM) is an idiopathic autoimmune inflammatory disorder characterised by a myopathy with a distinctive cutaneous eruption.
Skin lesions are frequently the initial presenting complaint, with muscle involvement developing later. Some patients have cutaneous involvement alone. Hallmark features include a heliotrope rash, Gottron's papules, photosensitivity, and nail fold capillary dilatation.
May be associated with interstitial lung disease, cardiac involvement, oesophageal involvement, dystrophic calcification, and underlying malignancy.
Initial treatment of muscle disease is with high-dose oral corticosteroids, followed by the addition of immunosuppressants or intravenous immunoglobulin in refractory cases.
Skin manifestations are treated with topical antipruritics and topical corticosteroids. Antimalarials and topical tacrolimus can be used in resistant disease.
Immunosuppressants and intravenous immunoglobulin are generally used for resistant and severe skin disease. Photoprotection is advised in all patients.
Dermatomyositis (DM) is an idiopathic autoimmune inflammatory myopathy characterised by distinctive skin manifestations. Diagnosis is based on the presence of a symmetrical proximal myopathy, raised muscle enzymes, myopathic changes on electromyography, a characteristic muscle biopsy, and a typical skin rash (e.g., periorbital dusky violaceous erythema, or macular violaceous erythema such as in V, shawl, and Gottron's signs). Some patients present with typical cutaneous manifestations but have delayed-onset, subclinical, or absent muscle disease. DM occurs in both adult and juvenile forms and can overlap with other connective tissue disorders (systemic sclerosis, systemic lupus erythematosus, mixed connective tissue disease, and, less often, rheumatoid arthritis and Sjögren's syndrome). It may be associated with interstitial lung disease, cardiac involvement, oesophageal involvement, dystrophic calcification, and underlying malignancy. Adult-onset DM is significantly associated with occult malignancy.
History and exam
Key diagnostic factors
- presence of risk factors
- Gottron's papules
- heliotrope rash with or without periorbital oedema
- macular violaceous erythema
- periungual erythema, nail-fold capillary dilation, cuticular overgrowth
- 'mechanic's' hands
- proximal muscle weakness
Other diagnostic factors
- poikiloderma vasculare atrophicans
- fatigue and malaise
- weight loss
- palpitations and syncope
- Raynaud's phenomenon
- cutaneous calcinosis
- vesicobullous lesions
- leukocytoclastic vasculitis
- cutaneous necrosis
- non-scarring alopecia
- genetic predisposition
- bimodal age distribution: children and age >40 years
- female sex
- black race
- ultraviolet radiation
- infectious agents
1st investigations to order
- serum creatine kinase (CK)
- serum aldolase
- muscle biopsy
- electromyogram (EMG)
- skin biopsy
- antinuclear antibody (ANA)
- myositis-specific antibodies (MSAs) and myositis-associated antibodies (MAAs)
Investigations to consider
- muscle MRI
- cardiac troponin I
- chest x-ray (CXR)
- pulmonary function tests (PFTs)
- high-resolution CT of chest
- barium swallow or video-fluoroscopic assessment of swallow
severe disease or acute flares
combined muscle and skin disease
skin disease only
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