Paraneoplastic Dermatomyositis Revealing the Metastatic Progression of an Undifferentiated Nasopharyngeal Carcinoma: A Case Report From Northern Morocco.

Dermatomyositis (DM) is an inflammatory disease of striated muscles and skin that can occur sporadically or rarely be associated with malignancy, thereby serving as a potential clinical indicator or harbinger of underlying cancer. Knowing the pathognomonic, clinical, and biological features of DM plays a pivotal role in its recognition. Its correlation with nasopharyngeal carcinoma (NPC) is particularly prevalent in regions where the incidence of NPC is notably high, underscoring the intricate interplay between immune dysregulation and oncogenesis. Specially, in the context of patients previously treated for NPC, the emergence of DM raises the clinical suspicion of metastatic progression or recurrence of the cancer. Thus, early recognition of DM-associated paraneoplastic syndromes can facilitate prompt intervention and optimize patient outcomes. We present a case of metastatic progression in a patient treated for NPC, revealed by the pathognomonic, clinical, and biological signs of DM.