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Dermatomyositis and polymyositis
Background
Overview
Definition
DM/PM are autoimmune myopathies characterized by subacute or chronic inflammation and weakness of proximal muscles with extra muscular manifestations.
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Pathophysiology
Dermatomyositis is mostly caused by humoral immune response whereas polymyositis is caused by T cell-mediated immune response.
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Disease course
Autoimmunity results in polymyositis (PM) and dermatomyositis (DM), which cause clinical manifestations of symmetrical proximal muscle weakness, pain, inflammation, typical rash in DM, fever, non-erosive arthritis, hyperkeratotic lesions along the radial and palmar aspects of fingers. Disease progression may lead to ILD and increased risk of malignancy.
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Prognosis and risk of recurrence
The in-hospital mortality rate of DM/PM is 4.58%.
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Guidelines
Key sources
The following summarized guidelines for the evaluation and management of dermatomyositis and polymyositis are prepared by our editorial team based on guidelines from the American College of Rheumatology (ACR 2023), the European League Against Rheumatism (EULAR 2023), the British Society for Rheumatology (BSR 2022), and the Japan College of Rheumatology (JCR 2019).
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