Hematological Conditions in Infants With Trisomy 21.

Virtually all neonates with Down syndrome (DS) have hematological abnormalities, including thrombocytopenia, polycythemia, and changes in the types and proportions of leukocytes. While many of these abnormalities are mild, they are important for neonatologists to be aware of, not only because some are life-threatening but also because they affect the interpretation of complete blood cell count results. The most serious hematological condition in neonates with DS is transient abnormal myelopoiesis (TAM), a neonatal leukemic syndrome unique to DS that is caused by mutations in the GATA1 transcription factor gene. In this review, we describe the spectrum of hematological conditions in neonates with DS and their implications, focusing primarily on TAM. We outline the approach to diagnosis and management of these conditions during the neonatal period and their significance for the health of these children in the short and long term. Lastly, we review the nonmalignant hematological abnormalities seen in neonates with DS, which are due to the effects of the extra 21 chromosome in the absence of GATA1 mutations.