The group of idiopathic inflammatory myopathies encompasses polymyositis, dermatomyositis and inclusion body myositis. These diseases share the following features: progressive muscle weakness, an increase in serum creatine kinase activity and the presence of mononuclear cell infiltrates in the muscle biopsy. Polymyositis, dermatomyositis and inclusion body myositis are differentiated on the basis of the distribution of muscle weakness, and specific histopathological features. Many specialties may see these patients as the clinical presentation can vary widely and may be atypical, requiring further diagnostic procedures. A 40-year-old man with a heliotrope rash and periorbital oedema, but no muscle involvement, was diagnosed with dermatomyositis sine myositis. He was successfully treated with corticosteroids but died later of cardiac failure. A 72-year-old man with a pulmonary malignancy subsequently developed the clinical features of dermatomyositis. Steroid therapy diminished the complaints but he died of pulmonary embolism. A 54-year-old woman with the clinical features of inclusion body myositis did not have rimmed vacuoles in her muscle biopsy specimen and was initially erroneously diagnosed with polymyositis, for which she was treated with corticosteroids, but without beneficial effect.