- Diagnosis of engraftment failure either primary or secondary, following allogeneic transplantation. Graft failure is defined as absolute neutrophil count < 500/mm3 and/or platelet count < 20,000/mm3. Primary graft failure is defined as failure to maintain absolute neutrophil count > / = 500/mm3 for 3 consecutive days following allogeneic transplantation. Secondary graft failure is defined as failure to sustain an absolute neutrophil count > / = 500/mm3 after attainment of primary engraftment or failure to sustain platelet count > / = 20,000/mm3 despite neutrophil engraftment. For SCID patients, graft failure is defined as failure to recover > / = 500/mm3 T-cells and/or failure to generate satisfactory response to in vitro mitogen stimulation. For patients with genetic diseases, engraftment failure is defined as donor chimerism insufficient to correct or overcome the genetic or metabolic deficiency.