Syndrome of inappropriate antidiuretic hormone secretion induced by tacrolimus following allogeneic cord blood transplantation.

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is an important electrolyte abnormality that can occur following allogeneic stem cell transplantation. We herein report the case of a 20-year-old man who developed SIADH three weeks after undergoing cord blood transplantation. Tacrolimus administration was suspected to be a cause of the disorder. In addition to restricting water intake and administering hypertonic sodium, the tacrolimus dosage was reduced, resulting in alleviation of SIADH. Therefore, tacrolimus should be recognized as an important, albeit rare, cause of drug-induced SIADH, even in patients with tacrolimus blood concentrations within the normal range. We believe that dose reduction, not discontinuation, is an effective strategy.