– This guideline presents recommendations for the diagnosis and treatment of dermatomyositis, polymyositis and sporadic inclusion body myositis (sIBM) according to the best available evidence.
– Characteristic skin abnormalities can be sufficient for the diagnosis of dermatomyositis. In case of doubt, a skin biopsy is advisable. A muscle biopsy is indicated when other examinations are inconclusive and the musculature is involved.
– The working group considers screening for cancer to be required in adults with dermatomyositis and presents recommendations for the way that this should be done.
– At least one-third of all patients with polymyositis has, or will develop, an associated inflammatory connective tissue disease. If a patient with a connective tissue disease develops symmetrical, proximal muscle weakness in the course of weeks or months, this may be assumed to be due to polymyositis. In the absence of pre-existing connective tissue disease, demonstration of a mononuclear cell infiltrate in muscle tissue is a prerequisite for the diagnosis of polymyositis.
– The histopathology of muscle tissue is used as the gold standard for the diagnosis of sIBM.
– The practice guideline presents criteria for the concept ‘activity’ of myositis. Disease activity serves as a guideline for the treatment of polymyositis and dermatomyositis.
– The treatment of choice for dermatomyositis and polymyositis is high-dose prednisone. Physical activity does not have a negative effect on the course of these diseases.
– The long-term prognosis of dermatomyositis and polymyositis is not well known. The clinical course of sIBM is slowly progressive.
Ned Tijdschr Geneeskd 2005;149:2104-11