[Salt-wasting nephropathy induced by foscarnet treatment for HHV-6 encephalitis in a hematopoietic stem cell transplant].

A 51-year-old woman with myelodysplastic syndrome developed HHV-6 encephalitis on day 34 after unrelated bone marrow transplantation. Although prompt treatment with foscarnet stabilized encephalitis and there were no serious neurological sequelae, the patient developed both hyponatremia and natriuresis 11 days after intravenous administration of foscarnet. Subsequent investigation demonstrated hyponatremia due to salt-wasting nephropathy induced by foscarnet. Discontinuation of foscarnet and fluid replacement therapy with adequate sodium chloride (NaCl) resulted in a gradual resolution of hyponatremia and natriuresis. Currently, 8 months after these clinical events, the patient is under outpatient treatment for persistent nephropathy that requires small amounts of oral NaCl supplement, but she is otherwise in good clinical condition.