Down syndrome is the most common chromosomal abnormality in humans with a frequency of 1 in 650 live births. Clinical manifestations are highly variable and depend largely on the presence of various genetic factors as mosaicism, copy number variants changes or single nucleotide variants. The identification of these variants has become a central topic of research, since it is essential for understanding the molecular mechanisms underlying this disease. KEYWORDS: Down syndrome; trisomy 21; Hsa 21; genomicsActa Pediatr Mex. 2016 sep;37(5):289-296. Genómica del síndrome de Down ResumenEl síndrome de Down es la cromosomopatía más común del ser humano, con una frecuencia de 1 en 650 recién nacidos vivos. Las manifestaciones clínicas son muy variables y dependen, en gran parte, de la presencia de diversos factores genéticos como mosaicismo, cambios variables en el número de copias o variantes de un solo nucleótido. La identificación de estas variantes se ha convertido en un tema central de investigación ya que es esencial para la comprensión de los mecanismos moleculares subyacentes en esta enfermedad.PALABRAS CLAVE: síndrome de Down, trisomía 21, Hsa21, genómica.
Background The 17p11.2p12 locus is an unstable region that is predisposed to several known genomic disorders and non-recurrent rearrangements that yield varied and wide-ranging phenotypes. Nearly 1% of male newborns have deletions in the Y chromosome; these events primarily involve the heterochromatic region, but may extend to euchromatic Yq segments containing azoospermia factor regions. Case presentation We describe the occurrence of two independent chromosomal rearrangements that originated as de novo events in a single male patient: a 10.8-Mb duplication of 17p11.2p12 and a 14.7-Mb deletion of Yq11. This individual shares some clinical characteristics with previously described patients having one or the other of these rearrangements, including global developmental delay, short stature, hypotonia, delayed puberty, certain facial features and a generalized demyelinating sensory-motor polyneuropathy without clinical manifestation. Our patient also presents some features that were not previously described in relevant individuals, including camptodactyly, preauricular pits and hypertrichosis of the back and elbows. Conclusions To our knowledge, this is the first patient to be reported with independent de novo deletion/duplication events involving chromosomes 17 and Y. We discuss possible responsible mechanisms and address the phenotype, particularly in light of the clinical features that were not previously reported for patients bearing a duplication of 17p11.2p12 or a deletion of Yq11. We suggest that some of the previously reported patients with Yq11 deletion and clinical manifestations other than male infertility may have additional chromosomal imbalances that could be identified by chromosome microarray analysis, as illustrated by the present case. Electronic supplementary material The online version of this article (10.1186/s13039-019-0438-0) contains supplementary material, which is available to authorized users.
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