Dermatomyositis (DM) is an autoimmune disorder of skin and muscle characterized by a broad spectrum of cutaneous manifestations. The dermatosis of DM may occur in isolation (clinically amyopathic DM) but myositis is usual and can lead to profound weakness. Involvement of the oro‐pharynx and the upper oesophageal sphincter in DM causes dysphagia. Aspiration pneumonia, exacerbated by respiratory muscle weakness, is the life‐threatening complication of oro‐pharyngeal involvement. There is a strong association between DM and internal malignancy, with studies indicating that up to one‐third of adult patients have an underlying cancer. Pathogenetically, DM is a humorally mediated microvasculopathy; the majority of patients have disease‐associated autoantibodies, notably the myositis‐specific antibodies (MSAs), including anti‐Mi‐2, TIF‐1γ, MDA‐5, Jo‐1 and SUMO activating enzyme. MSAs are specific for myositis and help define phenotype. Systemic corticosteroids are the primary treatment when both skin and muscles are involved. An immunosuppressant agent, such as azathioprine, methotrexate or mycophenolate mofetil, is usually needed to control the inflammatory activity and limit corticosteroid requirements. Intravenous immunoglobulin infusions can be effective for both muscle and skin activity. Antimalarials, topical corticosteroid and topical tacrolimus are variably useful in the management of DM skin disease.
Keywords dermatomyositis, amyopathic dermatomyositis, myositis, Gottron's papules, nail folds, shawl sign, poikiloderma, antisynthetase syndrome, myositis‐specific antibodies, myositis‐associated antibodies, immunosuppressants, intravenous immunoglobulin, autoimmune, interstitial lung disease, cancer