One theory is that autoimmune conditions start because of contact with a ‘trigger’, which makes the body’s immune system overreact. A variety of triggers may spark off events that lead to PM and DM and these include environmental factors such as sunlight, some infections or medications.
In some people, the trigger is an underlying cancer, which may already have been diagnosed, or might be discovered during the investigation of the myositis. Research has found that some people with myositis spectrum disorders have an increased risk of developing cancer. If you have any concerns about this, please get in touch with your specialist.