Mosaicism for trisomy 21: a review

Am J Med Genet A. 2015 Jan;167A(1):26-39. doi: 10.1002/ajmg.a.36861. Epub 2014 Nov 20.


The clinical and cytogenetic findings associated with mosaicism for trisomy 21/Down syndrome are the focus of this review. The primary topics discussed in this overview of the extant literature include the history of this condition and its diagnosis, the incidence of mosaicism, the meiotic and/or mitotic chromosomal malsegregation events resulting in mosaicism, the observation of mosaicism in the parents of children with the non-mosaic form of Down syndrome, and the variation in phenotypic outcome for both constitutional and acquired traits present in people with mosaicism for trisomy 21/Down syndrome, including cognition, fertility, and overall phenotypic findings. Additional topics reviewed include the social conditions of people with mosaicism, as well as age-related and epigenetic alterations observed in people with mosaicism for trisomy 21/Down syndrome. .

Keywords: Down syndrome; mosaic; mosaic Down syndrome; mosaicism; mosaicism for trisomy 21; trisomy 21.

Publication types

  • Historical Article
  • Review

MeSH terms

  • Down Syndrome / diagnosis
  • Down Syndrome / genetics*
  • Down Syndrome / history
  • Genetic Testing
  • History, 19th Century
  • Humans
  • Meiosis / genetics
  • Mosaicism*
  • Nondisjunction, Genetic
  • Phenotype