Single autosomal trisomy is a common numerical cytogenetic abnormality in hematological malignancies, and shows a predilection for myeloid disorders. While the strong morphologic correlation as for chromosomal translocations is lacking, phenotypic associations are observed for the trisomies. Trisomy 10 is associated with aberrant CD7 expression in acute myeloid leukemia (AML), and trisomy 13 is associated with immature subtypes of AML having hand-mirror blast morphology. Cytogenetic abnormalities have been shown to be the most valuable prognostic determinant in AML and myelodysplastic syndrome (MDS). Trisomy 8, the commonest of the trisomies in myeloid disorders, is associated with an intermediate prognosis, while poor clinical outcome has been described in AML with trisomy 11 and trisomy 13. Additionally, the presence of a trisomy allows the application of fluorescence in situ hybridization (FISH) techniques in monitoring therapy response, detection of minimal residual disease and determination of l ineage involvement. The role of trisomy in pathogenesis remains to be defined and a gene dosage effect has been suspected. The recent finding of MLL gene duplication in association with trisomy 11 represents the first documented gene rearrangement in this setting. Finally, whether single autosomal trisomy is a primary or secondary cytogenetic abnormality is presently unclear. Evidence in favor of a secondary change includes frequent association with well-defined structural changes and translocations, and appearance of trisomy with disease evolution. In this respect, it is interesting to note that trisomy may be a cytogenetic marker for an underlying cryptic gene rearrangement, for example trisomy 22 and CBFbeeta MYH11 fusion in AML. This review will summarize the current understanding of single autosomal trisomy in myeloid disorders.
Keywords: Single Autosomal Trisomy, Acute Myeloid Leukemia, Myelodysplastic Syndrome, Aberrant CD7 expression, Myeloid Leukemia AML, Fluorescence in situ hybridization, MLL Gene Duplication, Myeloid Disorders, Trisomy, Leukemogenesis