[Myeloid proliferations related to Down syndrome]

Down syndrome (DS) is related to constitutional trisomy 21 and is characterized by typical dysmorphic features and various congenital abnormalities. DS is also associated with a broad spectrum of hematological findings, such as transient thrombocytopenia in the neonatal period and acute leukemia. Of those hematological abnormalities, transient abnormal myelopoiesis (TAM) and acute myeloid leukemia (AML) have common genetic abnormalities, i.e., trisomy 21 and GATA1 mutation, and form a continuous spectrum, referred to as myeloid proliferations related to DS. Recent studies have demonstrated interactions between trisomy 21 and GATA1 mutations. Trisomy 21 promotes the expansion of early hematopoietic progenitors and upregulates short form GATA1, resulting in the accelerated production of aberrantly differentiated cells and development of TAM. Following spontaneous remission of TAM, subsequent AML can evolve from a preexisting residual TAM clone through the acquisition of additional mutations involving multiple cohesion components and epigenetic regulators.