Myelodysplastic Syndrome after Regression of Transient Abnormal Myelopoiesis in a Down Syndrome Infant: Different Clonal Origin?

A boy with Down syndrome who developed myelodysplastic syndrome after regression of transient abnormal myelopoiesis (TAM) is described. His blast cells in TAM had other chromosome abnormalities in addition to trisomy 21;50,XY,+21c,+12,+14,+21. Serial chromosome analysis in follow-up showed abnormal clones involving monosomy 7. Myelodysplastic syndrome was diagnosed. Because two clones had different karyotypes, they might have derived from different clones.