In a case report by Anzai et al. [14], the MCC and peripheral blood both had elevated adrenocorticotropic hormone (ACTH) levels, but the ACTH levels of the tumor were significantly lower than those of other ectopic ACTH-producing tumors, suggesting that the patient’s postoperative hyponatremia was caused by surgical stress and indapamide. Other dermatological and nondermatological malignancies presenting with dermatomyositis as paraneoplastic syndrome are listed in Table 1. Here, POMC is linked to Hyponatremia.