Stem Cell Transplant for Juvenile Myelomonocytic Leukemia (JMML)

Prior to transplantation, subjects will receive BUSULFAN via the central venous line, six times a day for four days, CYCLOPHOSPHAMIDE via the central venous line once a day for two days, and MELPHALAN via the central venous line for one day. Busulfan, cyclophosphamide, and melphalan are given to destroy the subject's leukemia. As well, these drugs will destroy the subject's own immune system to help ensure the new bone marrow takes and grows after transplantation. On the day of transplantation, bone marrow or umbilical cord blood from the donor will arrive to the bone marrow transplant unit and be transfused via venous line. These new cells will replace the subject's bone marrow.