While myositis doesn't cause cancer, physicians have found that a higher than normal percentage of dermatomyositis (DM) and polymyositis (PM) patients also have cancer. TMA's medical advisors suggest that newly diagnosed patients, especially those older than 50, be screened for cancer. When the cancer is successfully treated, the myositis symptoms often disappear. If there is more than a five-year lapse between the two diagnoses, they are not considered to be related.
More data are still required to determine individual cancer risks, although it appears that ovarian and lung cancer are associated with dermatomyositis while lung cancer and non-Hodgkin's lymphoma are associated with polymyositis. There is evidence that amyopathic dermatomyositis (DM without the muscle symptoms) also entails a higher-than-normal cancer risk.
Updated February 2014