Cortés-Gutiérrez EI, Hernández-Herrera R, Leal-Garza CH

Language: English
References: 17
Page: 105-107
PDF size: 57.07 Kb.

ABSTRACT

A rare variant of trisomy 21 is the “mirror image” duplication of chromosome 21. The possible mechanism for the formation of this chromosomal rearrangement is not known yet.
The clinical diagnosis of these patients usually presents no special difficulty. Nevertheless, the karyotyping, and the determination of the origin of this duplication can provide the basics for genetic counseling.
Clinical case. A baby with stigmata of Down syndrome was found to be a “mirror image” (reverse tandem) duplication of chromosome 21: 46, XX, der (21;21) (21pter→21q22: :2lq22→21pter) This chromosome rearrangement apparently appeared de novo.
Discussion. Four mechanisms are discussed for the origin of the abnormal chromosome: (a) exchange inter-intrachromosomal, (b) parapericentric inversion, (c) telomeric fusion between two chromosomes 21 and (d) translocation between two chromosomes in a trisomy 21 zygote.
The present report supports the association between trisomy of band 2lq22 and the Down phenotype.

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