Durable remission following a third allogeneic stem cell transplantation in a patient with repeatedly relapsing SAA. The importance of stroma cells for sustained engraftment?

Diagnosis of acquired AATP which finally progressed to SAA was established in an eight-yr-old boy. PBSCT from an HLA-identical unrelated donor using high numbers of CD34+ selected stem cells was performed and resulted in complete remission for almost two yr. However, SAA reoccurred with 100% donor hematopoiesis and was reversed by a second CD 34+ selected PBSCT from the same donor. Declining blood cell counts after an interval of two yr indicated second relapse. Chimerism analysis in PB and BM aspirates revealed a small autologous cell population of 4-12% and 2-11%, respectively. Finally, a third transplantation with unmanipulated BM from the same donor resulted in sustained remission with 100% donor hematopoiesis. The patient is in complete remission for more than five yr following the third SCT. Late graft failure or late graft rejection known to occur after transplantation of highly purified CD34+ cells, or even graft exhaustion caused by stromal dysfunction due to the underlying disease necessitated a third transplantation. Regardless of the cause of relapse, transplantation of unmanipulated BM instead of highly purified PBSCTs led to a permanent and stable engraftment in a third attempt after two previous PBSCTs.