Myeloid proliferation associated with Down syndrome

**Definition:** Myeloid neoplasms occurring in individuals with Down syndrome. There is an increased risk of acute leukaemias in both children and adults with Down syndrome. In particular, the incidence of acute myeloid leukaemia in Down syndrome children of less than five years of age is particularly high, it is usually an acute megakaryoblastic leukaemia, and is associated with GATA1 gene mutation. This group of disorders also includes the entity transient abnormal myelopoiesis which occurs in neonates and is associated with GATA1 gene mutation.