[Syndrome of inappropriate secretion of antidiuretic hormone in multiple myeloma patients treated with bortezomib, lenalidomide, and dexamethasone combination therapy].

Hyponatremia occurs while receiving bortezomib-containing combination therapy in multiple myeloma (MM) ; however, the mechanism of hyponatremia remains unclear. A 65-year-old female with MM was treated with bortezomib, lenalidomide, and dexamethasone. Fourteen days after chemotherapy initiation, she developed hyponatremia (serum sodium, 127 mEq/l, compared with 136 mEq/l before chemotherapy) with plasma hypo-osmolality and urine hyper-osmolality. She exhibited neither dehydration nor adrenal insufficiency. Her serum arginine vasopressin peptide (AVP) level was 1.5 pg/ml. She was diagnosed with syndrome of inappropriate secretion of antidiuretic hormone (SIADH), wherein causative roles of inflammatory cytokines were strongly suggested in the development because (1) SIADH was triggered by the cessation of the dexamethasone treatment and (2) hyponatremia was successfully treated with prednisolone, which was administered for the complication of drug eruption. Perhaps, bortezomib-induced immune reactions could be involved in a subset of hyponatremia during bortezomib-containing antimyeloma chemotherapy.