The effects of correction of vitamin D deficiency in children undergoing hematopoietic stem cell transplantation

   Literature data suggest that vitamin D (VD) deficiency may adversely affect many systems of the body, not only skeletal system, as believed earlier, but also central nervous system, cardiovascular system, urinary system, and immune system, which is particularly important for patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Two consecutive studies of VD deficiency after allogeneic HSCT in pediatric patients showed that VD deficiency was associated with decreased overall survival. The correction of VD deficiency was also reported to be a challenge, and in some cases higher doses of VD were needed (200 IU/kg/day or more), but even with this more aggressive approach VD deficiency could persist. In this article, we present a literature review on this topic as well as our data on the management of VD deficiency and monitoring of serum 25-hydroxycholecalciferol (25-HVD) levels in 18 children undergoing allogeneic HSCT at our hospital. This study was approved by the Independent Ethics Committee of the Regional Children's Clinical Hospital (Yekaterinburg). Unfortunately, because of the small size of the patient group we were not able to obtain reliable scientific data. However, here we present our approach to the clinical management of VD deficiency, personalized dosing of VD, and safe therapeutic ranges of VD metabolites in blood. The majority of HSCT recipients in our study achieved therapeutic levels of 25-hydroxycholecalciferol. Treatment of VD deficiency in children undergoing allogeneic HSCT is a promising way to improve overall survival, but further studies are needed to develop optimal clinical strategies.