Dermatomyositis is associated with an underlying malignancy in approximately 25% of patients. A weaker association is evident for polymyositis. The underlying malignancy is usually an adenocarcinoma of the ovary, lung, or gastrointestinal tract. Patients with dermatomyositis or polymyositis need to be evaluated uniformly for an underlying malignancy at the time of initial diagnosis and, in some cases, in the event of a subsequent recurrence. This apparent paraneoplastic syndrome may stem from an immune reaction to antigens expressed in cancer cells that crosses over to the same antigens expressed by regenerating fibers in damaged or diseased muscle.
- Paraneoplastic syndrome
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