Clonality switch in acute myeloid leukemia.

We have previously described a case of clonality switch in a female patient with acute myeloid leukemia (AML) by X-chromosome inactivation analysis. She presented with refractory anemia with excess blasts in transformation but soon progressed to overt AML. Following induction chemotherapy, she went into complete remission but later relapsed into a second myelodysplastic phase. Analysis of her X-linked DNA polymorphism patterns at presentation and relapse showed that hematopoiesis was clonal, but the genotypes of the two clones was different. She remains clinically well and has a virtually normal blood count more than 5 years from presentation. We now report an update of this unique case and discuss the implications of this finding within the context of a multicellular origin of leukemia.