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. 2022 Jan 24;15(1):1.
doi: 10.1186/s13039-021-00578-7.

Double aneuploidy mosaicism involving chromosomes 18 and 21 in a neonate

Christina Mendiola  1 , Veronica Ortega  1 , Allison Britt  2 , Rafael Fonseca  2 , Gopalrao Velagaleti  3
Affiliations

Double aneuploidy mosaicism involving chromosomes 18 and 21 in a neonate

Christina Mendiola et al. Mol Cytogenet. .

Abstract

Background: Double aneuploidy is common, especially in products of conception, frequently involving a combination of a sex chromosome and an acrocentric chromosome. Double autosomal trisomies are rare with only five cases reported. Double aneuploidy mosaicism involving two different cell lines is rarer with only three cases reported.

Case presentation: We report a fourth case of double aneuploidy mosaicism on a baby. Results of a 24-h preliminary chromosome analysis at birth showed a mosaic karyotype, 47,XX,+18[15]/47,XX,+21[8]/48,XX,+21,+mar[7]. Reflex testing to SNP microarray with the same sample collected at birth showed gain of a 77.9 Mb region on chromosome 18 and gain of a 32.5 Mb region on chromosome 21. Microarray did not show any other copy number variants indicating that the marker chromosome may not contain any euchromatic material. A repeat chromosome analysis at 1-year of age showed a mosaic karyotype, 47,XX,+18[76]/47,XX,+21[4] with loss of the marker cell line.

Conclusion: Based on our results, we propose that the mosaic double autosomal trisomy in our case was due to two independent non-disjunction events in a normal zygote very early during embryogenesis.

Keywords: Double aneuploidy; Non-disjunction; SNP microarray; Trisomy 18; Trisomy 21.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
GTG-banded karyotype at birth showing A trisomy 18, B trisomy 21 and C trisomy 21,+mar. FISH study at birth showing interphase nuclei with D trisomy 18 in AQUA and chromosome X in green and E trisomy 21 in orange
Fig. 2
Fig. 2
Karyoview at birth using Affymetrix CytoScan® HD array (ChAS 3.0), showing gains along the length of chromosome 18 (A). Segment view of chr.18 showing gain from 18p11.32 to 18q23 (B). Allele peaks showing 4 tracks (C) and Smooth signal showing gain (D)
Fig. 3
Fig. 3
Karyoview at birth using Affymetrix CytoScan® HD array (ChAS 3.0), showing gains along the length of chromosome 21 (A). Segment view of chr.21 showing gain from 21q11.2 to 21q22.3 (B). Allele peaks showing 4 tracks (C) and Smooth signal showing gain (D)
Fig. 4
Fig. 4
Hypothesized diagram showing mechanism of origin of double mosaic aneuploidy
See this image and copyright information in PMC

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