Severe cyclophosphamide-related hyponatremia in a patient with acute glomerulonephritis

Abstract

Cyclophosphamide is frequently used to treat cancer, autoimmune and renal diseases, such as rapidly progressive glomerulonephritis. Its side effects are well-known, including bone marrow depression, infections, alopecia, sterility, bladder malignancy and hemorrhagic cystitis. Moreover, in some cases cyclophosphamide use has been related to the onset of hyponatremia, by development of a syndrome of inappropriate antidiuresis. Indeed, severe hyponatremia has been previously reported in patients treated with high-dose or moderate-dose of intravenous cyclophosphamide, while only few cases have been reported in patients treated with low dose. Here, we discuss a case of a syndrome of inappropriate antidiuresis followed to a single low-dose of intravenous cyclophosphamide in a patient with a histological diagnosis of acute glomerulonephritis, presenting as acute kidney injury. After cyclophosphamide administration (500 mg IV), while renal function gradually improved, the patient developed confusion and headache. Laboratory examinations showed serum sodium concentration dropped to 122 mmol per liter associated with an elevated urinary osmolality of 199 mOsm/kg, while common causes of acute hyponatremia were excluded. He was successfully treated with water restriction and hypertonic saline solution infusion with the resolution of the electrolyte disorder. This case, together with the previous ones already reported, highlights that electrolyte profile should be strictly monitored in patients undergoing cyclophosphamide therapy in order to early recognize the potentially life-threatening complications of acute water retention.

Keywords: Hyponatremia, Cyclophosphamide, Syndrome of inappropriate antidiuresis, Glomerulonephritis, Hypertonic solutions, Antidiuretic hormone, Urine osmolality

Core tip: The syndrome of inappropriate antidiuresis (SIAD) is a disorder of sodium and water balance characterized by hypotonic hyponatremia and impaired urinary dilution in the absence of renal disease or any non-osmotic stimulus known to release anti-diuretic hormone. It may be caused by several conditions including infections, neoplasms and use of some medications, such as antipsychotics, antidepressant and immunosuppressive drugs. Here, we report the clinical course of a case of SIAD attributed to administration of a single low-dose of intravenous cyclophosphamide in a patient with an acute glomerulonephritis.