Busulfan-induced loss of Ph chromosome in chronic myeloid leukemia

We report a 44-yr-old female with Philadelphia chromosome positive chronic myeloid leukemia who was initially treated with busulfan, and clinical remission has been achieved. After 4 yr, low-dose busulfan therapy was started again and induced bone marrow aplasia. The patient spontaneously has recovered from aplasia, and complete cytogenetic remission with loss of Ph+ chromosome in bone marrow has been achieved. However, reverse-transcription-polymerase chain reaction analysis showed presence of the bcr-abl transcript in bone marrow.