In order to understand the genetic aspects / causes of myositis, and ultimately develop more effective treatment therapies in the future, patients with PM, DM or IBM, will be asked to give 20 mls of blood. These blood samples, along with the patient's clinical details, will then be sent to the Centre for Integrated Genomic Medical Research (CIGMR), at The University of Manchester, where all of the genetic analyses will take place. By understanding the genetic cause of the disease, it should be possible to design specific drugs for treating the condition in the future.