Hyponatremia and syndrome of inappropriate antidiuretic hormone secretion complicating stem cell transplantation.

Hyponatremia is a common electrolyte disorder in hospitalized patients. Although there are a few case reports of hyponatremia following stem cell transplantation (SCT), no reports concerning the incidence are currently available. We describe the occurrence of hyponatremia and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) following SCT. In a single center analysis of 140 patients, hyponatremia and SIADH were observed in 40 and 11.4% of patients, respectively, following SCT. Risk factors for SIADH included young age, transplantation from an HLA-mismatched or unrelated donor, cord blood transplantation, and graft-versus-host disease prophylaxis with methyl prednisolone. Multivariate analysis revealed that transplantation from an HLA-mismatched donor and performance of SCT in a child below 4 years of age were risk factors for SIADH. For patients who underwent SCT from an HLA-mismatched or unrelated donor, those with SIADH showed a significantly higher overall survival rate (90.9 vs 40.2%) and event-free survival rate (77.8 vs 33.8%) compared to those without SIADH. Overall, our data show that hyponatremia and SIADH are relatively common complications following SCT, especially in children below 4 years of age and after SCT from an HLA-mismatched donor.