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Leukemia - Acute

AML not otherwise categorized

Transient abnormal myelopoiesis (TAM)


Reviewer: Daniela Mihova, M.D. (see Reviewers page)
Revised: 2 February 2013, last major update September 2012
Copyright: (c) 2001-2013, PathologyOutlines.com, Inc.

General
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● 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
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● 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
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● Stillborn male fetus, gestational age 28 weeks, with severe disease (Nat Clin Pract Oncol 2007;4:433)
● Newborn (Hum Pathol 2000;31:396)

Treatment
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● Less intensive chemotherapy may be effective (J Clin Oncol 2007;25:5442)

Micro description
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● 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

Micro images
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Blasts in transient abnormal myelopoiesis of Down syndrome

Positive stains
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● CD4 (dim), CD7, CD13, CD33, CD34, CD36, CD41, CD42, CD56, CD61, CD71, CD117, TPO-R, IL-3R, HLA-DR (30%) (Am J Clin Pathol 2001;116:204)

Negative stains
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● CD11b, CD13, CD14, CD15, glycophorin A, myeloperoxidase and Sudan Black B

Molecular description
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● Trisomy 21 and acquired mutations in GATA1 gene in almost all cases (versus 4% of all Down syndrome infants, Blood 2007;110:2128), specific mutations may differ in TAM and subsequent AMKL (Int J Hematol 2007;86:250)
● Loss of GATA1 impairs maturation of megakaryocyte erythroid progenitors (Blood 2006;107:87)
● JAK3 mutations in 50% (Br J Haematol 2007;137:337)

End of Leukemia - Acute > AML not otherwise categorized > Transient abnormal myelopoiesis (TAM)


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