Paraneoplastic myalgias and myositis.

There are several key observations on paraneoplastic myopathies: The risk of cancer associated with DM is very high, whereas risk of cancer associated with PM is mildly increased Most cancers develop within one year of the onset of myositis, although the risk remains high up to 5 years after diagnosis. The most common cancers associated with DM are adenocarcinoma, including lung, ovary, cervical, stomach, pancreas, colorectal and lymphoma, whereas PM is associated with a high risk of lymphoma. The clinical course of myopathy is closely linked with the course of cancer. Certain clinical features are associated with CAM including severe treatment resistant skin manifestations, severe muscle weakness, respiratory muscle weakness, and dysphagia, while some clinical features are protective such as arthritis, Raynaud, and ILD. Screening should be based on age, gender, ethnicity, and the geographic area of the patient; however, certain high-risk patients may require more extensive screening including tumor markers and thoracoabdominal–pelvic CT scans. Certain autoantibodies including anti-p155 and the absence of more common autoantibodies are associated with a higher risk of CAM, while the presence of antisynthetase autoantibodies lowers the risk for CAM. Although the pathogenesis of CAM is unclear, a plausible hypothesis is that immune responses generated against antigens commonly targeted in myositis are related to antitumor responses in affected individuals.