Bone marrow neoplastic
Bone marrow - neoplastic myeloid
Transient abnormal myelopoiesis associated with Down syndrome

Topic Completed: 1 February 2013

Minor changes: 30 November 2020

Copyright: 2001-2021,, Inc.

PubMed Search: Transient abnormal myelopoiesis TAM

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Cite this page: Mihova D. Transient abnormal myelopoiesis associated with Down syndrome. website. Accessed March 2nd, 2021.
Definition / general
  • Myeloid proliferations related to Down syndrome (trisomy 21) include transient abnormal myelopoiesis (TAM) and Myeloid leukemia associated with Down syndrome; separate categories in WHO 2008
  • TAM occurs in 10% of Down syndrome newborns, clinical and morphologic findings indistinguishable from AML
  • Blasts morphologically and immunophenotypically are similar to megakaryocytic lineage
  • Down syndrome patients have increased risk for AML, usually AMKL (AML M7)
  • TAM usually resolves in 2 - 14 weeks in neonates, but 20 - 30% progress to AMKL within 3 years
  • TAM: early death in 17%, associated with high white blood cells at diagnosis, increased bilirubin and liver enzymes and failure to normalize white blood cells (Blood 2006;107:4606)
  • TAM rarely occurs without Down syndrome (Arch Dis Child Fetal Neonatal Ed 1998;79:F215)
Clinical features
  • 10% of newborns with Down syndrome but uncommon in neonates with trisomy 21 mosaicism
  • Thrombocytopenia, marked leucocytosis, %blasts in peripheral blood may exceed %blasts in bone marrow; also hepatosplenomegaly, cardiopulmonary failure, hyperviscosity, splenic necrosis and progressive hepatic fibrosis
Case reports
Microscopic (histologic) description
  • Blasts have moderate basophilic cytoplasm with cytoplasmic blebs, coarse azurophilic granules resembling those in basophils, round to slightly irregular nuclei
  • Also promegakaryocytes, micromegakaryocytes and dyserythropoiesis
  • Peripheral blood: White blood cells up to 100K with 30 - 50% blasts, nucleated red blood cells and micromegakaryocytes

Microscopic (histologic) images

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Blasts in transient
abnormal myelopoiesis
of Down syndrome

Positive stains
Molecular / cytogenetics description
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