Therapy-related myelodysplastic syndrome of recipient origin after allogeneic bone marrow transplantation for acute lymphoblastic leukaemia

Therapy-related myelodysplastic syndrome (t-MDS) is a very rare complicatio n of allogeneic bone marrow transplantation (BMT). A woman with T acute lym phoblastic leukaemia (T-ALL) received an allogeneic BMT from a donor with t he beta -thalassaemic trait. Five years after BMT, the red cell indices ret urned to normal after an initial conversion to microcytosis, implying autol ogous haematopoietic regeneration. Seven years after BMT, thrombocytopenia developed and marrow examination confirmed t-MDS, with a characteristic kar yotype 46,XX,inv(3)(q21;q26), del(5)(q13),add(17)(p11). Retrospective molec ular analysis of donor/recipient chimaerism showed gradual regeneration of recipient cells after BMT, culminating at the time of t-MDS. Our findings i llustrate the unusual occurrence of t-MDS after allogeneic BMT. Re-emergenc e of recipient haematopoesis may herald the development of a haematological malignancy different from the original neoplastic clone for which the BMT was performed.