Polymyositis and dermatomyositis are connective tissue diseases characterised by inflammation of muscles. Idiopathic inflammatory myopathies are a group of chronic, autoimmune conditions affecting primarily the proximal muscles. The most common types of myositis are dermatomyositis, polymyositis, necrotising autoimmune myopathy and sporadic inclusion body myositis (IBM).1
This is a companion discussion topic for the original article at https://patient.info/doctor/multisystem-diseases/myositis-polymyositis-and-dermatomyositis