Heterogeneous group of muscular disorders characterised by progressive muscle weakness.
Presentation is sub-acute or chronic and rarely acute.
May be associated with dysphagia, fatigue, difficulties with breathing, and skin lesions.
Diagnosis is confirmed by elevated serum muscle-derived enzymes, typical electromyography (EMG) findings, and inflammation on muscle biopsy.
Corticosteroids are first-line therapy. Intravenous immunoglobulin, methotrexate, and azathioprine are used as second-line therapy. Third-line therapies include cyclophosphamide, mycophenolate, ciclosporin, and tacrolimus.
Idiopathic inflammatory myopathies constitute a heterogeneous group of sub-acute, chronic, and, rarely, acute diseases of skeletal muscle that have in common the presence of moderate-to-severe proximal muscle weakness and inflammation on muscle biopsy. Based on distinct features, they are divided into 3 groups: polymyositis, dermatomyositis, and inclusion body myositis. Polymyositis and dermatomyositis seem to have an autoimmune pathogenesis, whereas inclusion body myositis seems to have an autoimmune and degenerative pathogenesis.
History and exam
- frequent falls
- fatigue and generalised malaise
- weight loss
- shortness of breath
- mild fever
- abnormal breath sounds
- symptoms of MI
- facial rash
- erythematous rash
- nail fold changes
- facial muscle weakness
- skin calcinosis
- joint swelling
- signs of heart failure and/or MI
- physical findings of malignancy
- systemic signs of autoimmune disease
- peripheral neuropathy
- children and age >40 years
- exposure to high intensity of global UV radiation
- genetic predisposition
- female sex and/or black ethnicity (polymyositis and dermatomyositis)
- male sex and/or white ethnicity (inclusion body myositis)
- lipid-lowering agents
- viral infections (excluding HIV)
- non-viral infection
- other drugs or toxins
Associate Professor of Neurology
Rutgers, The State University of New Jersey
New Jersey Medical School
NS declares that he has no competing interests.
Department of Neurology
Penn Presbyterian Medical Center
University of Pennsylvania Health System
SK declares that he has no competing interests.
Department of Neurology
Brigham and Women's Hospital
Harvard Medical School
AAA declares that he has no competing interests.
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