Clinical characterization and genetic analysis of transient abnormal myelopoiesis without Down syndrome phenotype

This case study describes transient abnormal myelopoiesis (TAM) in a neonate with trisomy 21 and GATA1 mutation but lacking typical Down syndrome features; the condition resolved spontaneously without chemotherapy. A literature review of 13 similar cases demonstrates that TAM can present with mosaic or acquired trisomy 21 confined to hematopoietic cells, with self-limiting remission and favorable long-term prognosis.