Development of acute megakaryoblastic leukemia from a minor clone in a Down syndrome patient with clinically overt transient myeloproliferative disorder.

A Down syndrome male showed leukocytosis from birth and was diagnosed as transient myeloproliferative disorder (TMD). Eight months later, his condition had progressed to myelodysplastic syndrome after spontaneous resolution, and it then evolved to acute megakaryoblastic leukemia (AMKL) at the age of 20 months. Sequencing analysis showed that the predominant TMD and AMKL clones had different GATA1 mutations, although a minor TMD clone identical to the AMKL clone was present at birth. These observations suggest that a minor clone rather than the predominant clone at the time of TMD may give rise to AMKL later on.