A case of primary adrenal diffuse large B cell lymphoma presenting with severe hyponatremia.

We herein report a case of primary adrenal lymphoma with severe hyponatremia. The patient was admitted for an evaluation of severe hyponatremia and an enlarged bilateral adrenal mass, which were found in a previous examination for causes of general fatigue and anorexia. Laboratory data, including the serum levels of sodium (115 mEq/L), osmolality (239 mOsm/kgH2O), ADH (5.8 pg/mL), cortisol (11.6 µg/dL), free T3 (2.42 pg/mL), urinary Na (117 mEq/L) and urine osmolality (490 mOsm/kgH2O), fulfilled the diagnostic criteria for the syndrome of inappropriate secretion of ADH (SIADH). An abdominal computed tomography scan revealed a large bilateral adrenal mass. A biopsy of the enlarged left adrenal mass revealed diffuse large B cell lymphoma, which was negative for ADH protein. Hydrocortisone treatment normalized the patient's body temperature and serum sodium concentration. In this case, hyponatremia developed when both adrenal glands were involved and was normalized with hydrocortisone. These findings suggest that adrenal insufficiency was the cause of hyponatremia, although the basal serum cortisol was normal. The current case suggests that the administration of hydrocortisone is recommended if suspicious clinical signs or symptoms are found in severe hyponatremia, even if hyponatremia is associated with a normal serum cortisol level and fulfills the diagnostic criteria for SIADH.