BACKGROUND: Syndrome of inappropriate antidiuresis is characterized by euvolemic hyponatremia due to inappropriate secretion or elevation of antidiuretic hormone or arginine vasopressin. Patients with small cell lung cancer are especially prone for this complication and multiple randomized control trials have shown an improvement in sodium with tolvaptan.
CASE: We report a 61-year-old-male patient with small cell lung cancer who presented with to the hospital multiple times with acute on chronic symptomatic hyponatremia. The patient showed a good response to tolvaptan but subsequently developed resistance as a result of progression of lung cancer with metastasis to liver.
CONCLUSION: In cases of paraneoplastic effects of lung cancer, hyponatremia is an important manifestation from syndrome of inappropriate antidiuresis. Hyponatremia, in these patients, is associated with significant morbidity and mortality and treatment includes surgery, chemotherapy or radiation therapy for the cancer, tolvaptan for hyponatremia and in cases of progression of cancer, addition of salt tablets or loop diuretics may be necessary
