Successful engraftment after infusion of multiple low doses of CD34+ cells from a poorly matched sibling donor in a patient with severe aplastic anemia

The dose of CD34+ cells is known to influence the outcome of allogeneic peripheral blood stem cell (PBSC) and/or T-cell-depleted transplantation. A previous study proposed that $2{\times}10^6\;CD34+\;cells/kg$ is the ideal minimum dose for allogeneic transplantation, although lower doses did not preclude successful therapy. In the case we present here, CD34+ cells were collected from a matched sibling donor on the day of allogeneic hematopoietic stem cell transplantation; however, the number of cells was not sufficient for transplantation. Consequently, PBSCs were collected three additional times and were infused along with cord blood cells from the donor that were cryopreserved at birth. The cumulative dose of total nuclear cells and CD34+ cells was $15.9{\times}10^8\;cells/kg$ and $0.95{\times}10^6\;cells/kg$, respectively. White blood cells from this patient were engrafted on day 12. In summary, we report successful engraftment after infusion of multiple low doses of CD34+ cells in a patient with severe aplastic anemia.