Génétique humaine et Embryologie

A Baby With Double Aneuploidy Mosaicism

Abstract

Tim David

Double aneuploidy is prevalent, especially in conceived products, and is commonly caused by the combination of a sex chromosome and an acrocentric chromosome. Only five examples of double autosomal trisomy have been recorded. Only three occurrences of double aneuploidy mosaicism involving two separate cell lines have been recorded. A fourth occurrence of double aneuploidy mosaicism on a newborn is reported. A preliminary 24-hour chromosomal study at delivery revealed a mosaic karyotype, 47,XX,+18[15]/47,XX,+21[8]/48,XX,+21,+mar[7]. Reflex testing to SNP microarray with the same material obtained at birth revealed chromosome 18 increase of 77.9 Mb and chromosomal 21 gain of 32.5 Mb. The microarray revealed no further copy number alterations, implying that the marker chromosome does not contain any euchromatic material. At one year of life, a repeat chromosome analysis revealed a mosaic karyotype, 47,XX,+18[76]/47,XX,+21[4], with loss of the marker cell line. Double aneuploidy is prevalent, particularly in conceived products, and typically involves a sex chromosome and an acrocentric chromosome.