3.2. Stable mixed chimerism
MC was diagnosed in four children. In two of them, the number of host cells was relatively small (6 and 2% in UPN 141 with SAA and UPN 191 with CGL, respectively). No GvHD was diagnosed and they are both alive with no evidence of disease and high Karnofsky score. Patient UPN 108 with SAA developed progressive poor graft function (trombocytopenia and anemia with absence of erythropoesis later accompanied by neutropenia requiring G-SCF) despite being stable MC (60% donor) for almost 2 years after the first transplant. A secondary graft failure was diagnosed and the patient was retransplanted from the same donor with intensified conditioning employing fludarabine, cyclophosphamide and ATG. After the second transplant, she developed stable CC and good engraftment. SCID patient UPN 121 was a stable mixed chimera, but with T cells exclusively of donor origin. The child developed aGvHD grade II and is alive with corrected immune function. However, he experienced late pulmonary complication (brionchiolitis obliterans) and requires repeated pulses of high-dose steroids.