Schwartz-Bartter Syndrome: A Subtle Complication of Small Cell Lung Carcinoma

Paraneoplastic syndromes are defined as a conglomerate of clinical disorders that are caused by neoplastic diseases, specifically lung cancer. The clinical symptomatology of paraneoplastic syndromes usually precedes the diagnosis of the associated neoplasm, however, according to our current literature; the extent of the symptoms is not associated with the size of the tumor. Syndrome of inappropriate anti-diuretic hormone release (SIADH), also known as Schwartz-Bartter syndrome, is commonly caused by small cell lung carcinoma (SCLC) and is characterized by euvolemic hypoosmolar hyponatremia, which will lead to a low serum osmolality as well as a significantly high urine osmolality in the absence of other medical conditions such as adrenal insufficiency, heart failure, cirrhosis, and diuretic syndrome among others. The clinical presentation related to SIADH varies based upon the severity of the hyponatremia as well as the acuteness of the decrease in serum sodium levels. Symptoms due to SIADH include anorexia, nausea, vomiting, and in more severe cases, cerebral edema due to rapid of onset hyponatremia thus causing confusion, restlessness, coma, seizures, and respiratory arrest.