GATA1 and Down syndrome: This presentation of the constitutional SH2B3-related disease is reminiscent of that observed in other MPD in neonates or infants, such as in patients with Down syndrome with somatic mutations in GATA1, or in RASopathies associated with germline mutations in CBL or PTPN11. In particular, MPD in CBL syndrome characterized by monoallelic germline mutation and LOH in hematopoietic cells, runs a self-resolving clinical course in the vast majority of cases.