A bone marrow disorder that can occur in newborns who have Down syndrome. It is marked by abnormal, immature blood-forming cells in the blood and bone marrow (especially the cells involved in making platelets). The liver may also be larger than normal. TAM is caused by mutations (changes) in a gene called GATA1. TAM usually goes away on its own within the first 3 months of life. Sometimes TAM causes severe or life-threatening problems, such as bleeding problems, infection, heart, kidney, and liver failure, and abnormal build-up of fluid in the tissues that cover the organs in the body. Infants who have TAM have an increased risk of developing acute myeloid leukemia (AML) before the age of 3 years. Also called TMD, transient abnormal myelopoiesis, transient leukemia, and transient myeloproliferative disorder.