Engraftment-associated hypophosphatemia - The role of cytokine release and steep leukocyte rise post stem cell transplantation

Hypophosphatemia associated with bone marrow transplantation has been infrequently reported. The suggested mechanism is phosphate uptake by the replicating cells. Various cytokines are associated with the development of hypophosphatemia. The present study evaluated the interrelationship between cytokine release, the rise in WBC and the development of hypophosphatemia during the engraftment period. Blood samples were obtained from 60 patients undergoing peripheral blood stem cell transplant, on the day of admission and then daily from the day of transplant until discharge. Hypophosphatemia developed in 62% of the patients. The median day of minimal phosphorus level was +8 and it antedated engraftment by 2 days. There was a significant correlation between the day of minimal phosphorus level and the day of maximal WBC and a significant correlation between the fall in phosphorus level and WBC rise. IL-6 and IL-8 showed similar kinetics. Higher IL-6 and IL-8 levels were directly associated with lower phosphorus levels. In conclusion, hypophosphatemia commonly occurs in the post-transplant period. We assume that both a direct effect of cytokine release and an increased consumption by the dividing WBCs contribute to its appearance. As its occurrence usually antedates engraftment it can be used as a forerunner for WBC recovery.