The inflammatory myopathies – polymyositis, dermatomyositis, inclusion body myositis and immune-mediated necrotising myopathy – are rare but in many cases, treatable causes of muscle weakness.
The inflammatory myopathies are a group of rare conditions that usually present in general practice as a patient with muscle weakness and/or an elevated serum creatine kinase (CK) level. Possible extramuscular manifestations include skin rashes, fever and weight loss. Recently there have been important advances in our understanding of these conditions and in their management. The group includes polymyositis, dermatomyositis, inclusion body myositis and immune-mediated necrotising myopathy (also known as necrotising autoimmune myopathy and a potential drug side effect). These conditions are differentiated on the basis of their pattern of presentation, patient age at onset and immunohistopathologic features.