The idiopathic inflammatory myopathies represent a rare group of diseases characterized by autoimmune inflammation of skeletal muscle and other organs. There has been significant recent progress in understanding pathogenesis, phenotyping disease subtypes and investigating effective therapeutic options. Patients typically present with progressive, proximal weakness and elevated muscle enzymes, and often have additional extramuscular manifestations, including skin, respiratory, articular, gastrointestinal and cardiovascular involvement. These extramuscular manifestations can precede or occur in the absence of clinically detectable muscle involvement. There are a multitude of potential differential diagnoses to consider and a careful initial evaluation supported by structured investigations remains critical for accurate diagnosis and timely commencement of appropriate treatment.