• Clinical science

Chromosomal aberrations

Abstract

Structural and numerical chromosomal aberrations may affect either the autosomes or gonosomes and are a common cause of spontaneous abortions. Autosomal aberrations that are frequently observed are trisomy 13 (Patau syndrome), trisomy 18 (Edwards syndrome), and the most common and widely recognized chromosomal aberration, trisomy 21 (Down syndrome). These conditions have an extra copy of the chromosome to which their name refer. The risk of autosomal aberrations increases with maternal age. Characteristic features include facial and skeletal malformations, which are usually recognizable at birth. The conditions are further associated with congenital heart defects and malformations of other internal organs. Turner syndrome and Klinefelter syndrome are gonosomal aberrations in which individuals have a missing X chromosome or an additional X chromosome, respectively. These conditions are primarily characterized by impaired development of secondary sexual characteristics and infertility secondary to gonadal dysgenesis. The diagnosis for all chromosomal aberrations is confirmed via karyotyping.

General information

Definitions

  • Chromosomal aberrations: deviation from the normal chromosome constellation
    • Numerical chromosomal aberrations; (e.g., aneuploidy, polyploidy)
    • Structural chromosomal aberrations; (e.g., deletion, translocation)
  • Triploidy: : presence of three sets of chromosomes
  • Trisomy: : presence of triplicate instead of duplicate number of a particular chromosome or part of a chromosome

Epidemiology

  • Chromosomal aberrations are the most common cause of spontaneous abortions (accounting for 60% of cases).
    • Approx. 50% of anomalies are trisomies.
    • Approx. 20% of anomalies are triploidies.

Overview of viable numerical chromosomal aberrations

References:[1]

Trisomy 13 (Patau syndrome)

References:[2][3][4][5][6][7][8]

Trisomy 18 (Edwards syndrome)

References:[3][6][8]

Down syndrome (trisomy 21)