Marrow aplasia developing 3 years after treatment with busulphan for chronic myeloid leukaemia

A 31-year-old woman with Philadelphia chromosome-positive chronic myeloid leukaemia (CML) was treated intermittently with high-dose busulphan over a 6-yr period (total dose 1320 mg). 3 yr later (after receiving no further cytotoxic drugs) she developed pancytopenia and marrow aplasia of relatively abrupt onset. Transfusion of reconstituted blood-derived stem cells (collected 7 yr previously) re-established chronic phase CML. These events are more consistent with 'stem cell exhaustion' than with an acquired marrow microenvironmental defect occurring in the course of CML. The contribution of busulphan is uncertain.