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Chromosomal aberrations

Last updated: July 15, 2021

Summarytoggle arrow icon

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.

Definitions

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.

Viable numerical chromosomal aberrations

Overview of autosomal chromosomal aberrations
Trisomy 13 (Patau syndrome) Trisomy 18 (Edwards syndrome) Trisomy 21 (Down syndrome)
Karyotype
  • : 47,XX,+13
  • : 47,XY,+13
  • : 47,XX,+18
  • : 47,XY,+18
Pathogenesis

Clinical features

Associated conditions

Neurocognitive deficiency

  • Variable (average IQ: 50)
Life expectancy
  • < 12 months of age
  • < 12 months of age
  • Decreased (∼ 60 years)

The age of Puberty onset is 13: Patau syndrome is caused by trisomy 13.

7 Ps of Patau syndrome: holoProsencephaly, cleft liP and Palate, Polydactyly, Pump disease (congenital heart disease), Polycystic kidney disease, cutis aPlasia.

PRINCE Edward turned 18: Prominent occiput, Rocker-bottom feet, Intellectual disability, Nondisjunction (in meiosis), Clenched fists, low-set Ears, and chromosome 18.

See article on “Down syndrome.”

  1. XYY Syndrome. https://rarediseases.org/rare-diseases/xyy-syndrome/. Updated: January 1, 2012. Accessed: March 6, 2017.
  2. Trisomy X. https://rarediseases.org/rare-diseases/trisomy-x/. Updated: January 1, 2014. Accessed: March 6, 2014.
  3. 47,XYY syndrome. https://ghr.nlm.nih.gov/condition/47xyy-syndrome#statistics. Updated: February 14, 2017. Accessed: February 16, 2017.
  4. triple X syndrome. https://ghr.nlm.nih.gov/condition/triple-x-syndrome#statistics. Updated: February 14, 2017. Accessed: February 16, 2017.
  5. Otter M, Schrander-stumpel CT, Curfs LM. Triple X syndrome: a review of the literature. Eur J Hum Genet. 2009; 18 (3): p.265-271. doi: 10.1038/ejhg.2009.109 . | Open in Read by QxMD
  6. Data & Statistics on Birth Defects. https://www.cdc.gov/ncbddd/birthdefects/data.html. Updated: January 23, 2020. Accessed: June 29, 2020.
  7. Meyer RE, Liu G, Gilboa SM, et al. Survival of children with trisomy 13 and trisomy 18: A multi-state population-based study. American Journal of Medical Genetics Part A. 2015; 170 (4): p.825-837. doi: 10.1002/ajmg.a.37495 . | Open in Read by QxMD