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Am J Med Genet A. 2017 Dec;173(12):3153-3157. doi: 10.1002/ajmg.a.38497. Epub 2017 Oct 19.

Beyond Down syndrome phenotype: Paternally derived isodicentric chromosome 21 with partial monosomy 21q22.3.

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Department of Obstetrics and Gynecology, Detroit Medical Center/Wayne State University, Detroit, Michigan.
Department of Obstetrics, Gynecology, and Reproductive Sciences, Magee-Womens Hospital, University of Pittsburgh, Pittsburgh, Pennsylvania.
Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania.
Magee-Womens Research Institute, Pittsburgh, Pennsylvania.
Genescreen, Pittsburgh, Pennsylvania.


Inverted isodicentric chromosome 21 is a rare form of chromosomal rearrangement that may result in trisomy 21; sometimes this rearrangement may also lead to segmental monosomy of the terminal long arm of chromosome 21. In this report, we describe the prenatal diagnosis and neonatal follow-up of a child with a paternally derived, de novo isodicentric chromosome 21 and a concurrent ∼1.2 Mb deletion of the 21q22.3 region [46,XX,idic(21)(q22.3)]. This child presented with unusual phenotype of Down syndrome and additional defects including esophageal atresia and tethered cord syndrome. The resulting phenotype in this infant might be a coalescence of the partial trisomy and monosomy 21, as well as homozygosity for idic (21). The utilization of chromosomal microarray in this case enabled accurate characterization of a rare chromosome abnormality, potentially contributes to future phenotype-genotype correlation and produced evidence for a molecular mechanism underlying this rearrangement.


21q22.3 deletion; chromosomal microarray analysis (CMA); isodicentric 21; partial trisomy 21; prenatal diagnosis

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