Early onset of syndrome of inappropriate antidiuretic hormone secretion (SIADH) after allogeneic haematopoietic stem cell transplantation: case report and review of the literature.

Severe hyponatraemia and syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a rare but fatal complication following stem cell transplantation (SCT). This case report details a patient with early-onset SIADH after allogeneic haematopoietic SCT (allo-HSCT) and reviews the literature on risk factors for the development of this condition. The patient, who had chronic myelogenous leukaemia, developed acute graft-versus-host disease (GVHD) on day 5 after allo-HSCT, which was relieved promptly by steroids. On day 18, he presented with hyponatraemia, which was refractory. Despite intensive restriction of fluid and administration of hypertonic saline, his condition worsened and he died of multiple systemic organ dysfunction. A review of the literature reveals that early-onset SIADH following SCT is insidious, but progresses rapidly. The severity of the disorder is underestimated because of the non-specific clinical features and the lack of effective treatment. Myeloablative conditioning and acute GVHD are two major important predisposing factors in SIADH.