Paraneoplastic dermatomyositis accompanying nasopharyngeal carcinoma: diagnosis, treatment and prognosis.

Dermatomyositis (DM) is a multisystem inflammatory disorder primarily affecting the skin and muscles. Its pathophysiology is still very poorly understood, but humoral and cellular immune dysregulation is apparent. Diagnosis of DM is based on five criteria: proximal limb muscle weakness, serum muscle enzyme elevation, histopathologic muscle abnormalities on muscle biopsy, electromyographic abnormalities, and clinical inflammatory dermatological manifestations (heliotrope rash, poikiloderma, and inflammatory lesions on the hands and facing joints). DM is frequently associated with certain cancers, and may appear before, concurrent with, or after diagnosis of cancer. DM has been reported to be associated with approximately one per 1000 cases of nasopharyngeal carcinoma. Treatment is based on long-course nonselective immunosuppression, particularly corticosteroids, by general route, even when malignancy is present, but new-targeted therapies may modify the treatment strategy in the near future. Despite iatrogenic immunosuppression, the prognosis of nasopharyngeal cancer is not worse in patients with paraneoplastic DM. We report one case as an illustration of this paraneoplastic course (evolving in parallel with the cancer), and to make an update on the state of knowledge on paraneoplastic DM in such cancers.