Edward's Syndrome (Trisomy 18)

Original Editor - Anna Fuhrmann Top Contributors - Niha Mulla, Anna Fuhrmann and Kirenga Bamurange Liliane

Definition[edit | edit source]

Edward's Syndrome, also known as Trisomy 18, is a rare genetic condition caused by a triplication of the 18th chromosome. The additional chromosome causes a complex congenital malformation syndrome predominantly affecting inner organs, overall growth and anatomical anomalies. Most babies which carry the disease die either before birth or within the first days of their life, only around 13 out of 100 survive their first birthday.[1] Very few children survive longer than five years, and in those cases are severely impaired in their cognitive function and intellectual abilities.[2][3]

Chromosome pairs of a person with Edward's Syndrome (Trisomy 18).Source: Serra Amoros, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

Types of Edwards Syndrome

  • Full Edward's Syndrome (Three complete sets of the 18th chromosome): Most severe type of the disease, highest mortality rate.[1]
  • Mosaic Edward's Syndrome (Trisomy only appears in some cells): Severity of the condition depends on the number and types of affected cells, some children may live to adulthood.
  • Partial Edward's Syndrome (Partial trisomy 18, only sections of the 18th chromosome are tripled): Severity of the condition depends on which section of the 18th chromosome is tripled.

Prevalence[edit | edit source]

Around 1/5,000 - 1/6,000 children which are born alive have Edward's Syndrome.[4][5] Sadly, most babies carrying the Full Edward's Syndrome die before birth. Prevalence is lower for the types of Mosaic Edward's Syndrome (1/20) and Partial Edward's Syndrome (1/100) out of all children born with Edward's Syndrome.[1] The male-female ratio is 1:3.[5]

Etiology[edit | edit source]

The additional chromosome is most commonly not inherited, but an effect of spontaneous malformation during cell division.[6] In few cases of inheritance from the mother's side, mostly happening in Partial Edward's Syndrome.

Cause of Edwards' syndrome[edit | edit source]

Each cell in human body contains 23 pairs of chromosomes which carry the genes. A baby with Edwards' syndrome has 3 copies of chromosome number 18 instead of 2.This in turn affects the way the baby grows and develops.

Presence of three copies of genes on chromosome 18 instead of two happens by purely by chance and in no way runs in families, because of a change in the sperm or egg before a baby is conceived. The chances of this change happening increases with increasing age. [1][6][7][8][9][10]

Characteristics / Clinical Presentation[edit | edit source]

There are no specific criteria for clinically diagnosing children with Trisomy 18 since presentation can vary drastically, depending on the severity of the condition. Typical symptoms however include:

  • Low birth weight and small body[7]
  • Little intrauterine movement of the fetus
  • Abnormalities of body shape (especially microcephaly, prolonged back of the head, short sternum)
  • Organ deformities and malfunctions
  • Fisted fingers, crossed fingers (thumb and small fingers cross other fingers)
  • Rocker bottom feet or club feet
  • Problems with feeding, breathing.[7][9]
  • Heart defects. [9]
  • Elbows and knee joints are in a bent position instead of being relaxed[9]
  • Some babies with Edwards syndrome may also have spina Bifida, cleft lip and palate, eye problems and hearing loss.[9]
  • Seizures, hernias, scoliosis, kidney disease may all be present at birth or develop within the first year of life.

Diagnosis[edit | edit source]

  • Edwards syndrome can be suspected and diagnosed during pregnancy, during or after 10 to 14 -weeks by a pregnancy ultrasound and blood test.The screening is mostly paired with a screening for Down Syndrome and Patau's Syndrome.[1]
  • Possibility of Edwards syndrome is screened through non-invasive prenatal testing (NIPT), which is a blood test taken from 10 weeks of pregnancy.[7][9]
  • If an increased risk of Edward's Syndrome is presented, invasive testing will be offered either through chorionic villus sampling (analysing placenta cells) or amneocentesis (sampling the amniotic fluid). Invasive tests increase the risk of miscarriage and need to be thoroughly discussed with the parents. [8][9]
  • Genetic testing is the only way to confirm the diagnosis of Edwards syndrome.
  • In some instances, Edwards syndrome is not suspected during pregnancy, and is only discovered when the baby is born. If doctor believes the baby has Edwards' syndrome after they're born, a blood sample is taken to see if there are extra copies of chromosome 18.
  • Pre-natal screening is vital so there can be an early diagnosis.[1][7]

Prevention[edit | edit source]

Edwards syndrome happens as a result of a genetic mutation and there’s no way to prevent it from happening. Genetic counseling and genetic testing can prove to be helpful for early diagnosis.[8][9]

Treatment[edit | edit source]

  • The condition is usually so severe that babies who survive being born with Edwards syndrome (trisomy 18) are treated with comfort/ palliative care.[7]
  • Treatment is unique for each child, based on the severity of their diagnosis and there is no cure.
  • Therapy and medical management focus on supporting the family and the babies' acute impairments.

Some forma of treatment for Edwards syndrome include:[8][9]

  1. Cardiac treatment: Heart problems affect nearly all cases of Edwards syndrome while only very few qualify for surgery to get the condition treated.
  2. Assisted feeding: Infants with Edwards syndrome have problems eating due to delayed physical growth and feeding tube might be necessary to help the baby get nutrition.
  3. Orthopedic treatment: Treatment involves surgery or bracing for scoliosis and other joint issues.
  4. Psychosocial support: To help cope with the loss of the child or navigate through child’s complex diagnosis, mental and emotional health support us vital.

Prognosis[edit | edit source]

  • Almost all pregnancies with Edwards syndrome end in a miscarriage or stillbirth.[8]
  • One half of infants with this condition do not survive beyond the first week of their life.
  • 60% and 75% of the infants survive only the first week.
  • 20% and 40% survive to their first month.
  • Nine out of ten children die by 1 year of age with only 10% surviving past their first year of life. [9]
  • Some children have survived to the teenage years, but with serious medical and developmental issues.

References[edit | edit source]

  1. 1.0 1.1 1.2 1.3 1.4 1.5 National Health Service, Edward's syndrome (trisomy 18), Sept 2020, Available from: https://www.nhs.uk/conditions/edwards-syndrome/, [last accessed 12 March 2022].
  2. Cereda A, Carey JC. The trisomy 18 syndrome. Orphanet journal of rare diseases. 2012 Dec;7(1):1-4.
  3. Wu J, Springett A, Morris JK. Survival of trisomy 18 (Edwards syndrome) and trisomy 13 (Patau Syndrome) in England and Wales: 2004–2011. American Journal of Medical Genetics Part A. 2013 Oct;161(10):2512-8.
  4. DocCheck Flexikon, Edwards Syndrom, 18. April 2011, Available from: https://flexikon.doccheck.com/de/Edwards-Syndrom [last accessed 12 March 2022].
  5. 5.0 5.1 MSD Manuals, Trisomie 18, Okt 2018, Availabe from: https://www.msdmanuals.com/de-de/profi/p%C3%A4diatrie/chromosomen-und-genanomalien/trisomie-18 [last accessed 12 March 2022].
  6. 6.0 6.1 Medline Plus - National Library of Medicine (NIH), Trisomy 18, Feb 2021, Available from: https://medlineplus.gov/genetics/condition/trisomy-18/#inheritance [last accessed 12 March 2022].
  7. 7.0 7.1 7.2 7.3 7.4 7.5 Edwards syndrome (trisomy 18). Healthdirect Australia. 2020 . Available from: https://www.healthdirect.gov.au/edwards-syndrome-trisomy-18
  8. 8.0 8.1 8.2 8.3 8.4 Edwards syndrome (trisomy 18): Genetic condition, symptoms & outlook. Cleveland Clinic. 2021 Dec 12 . Available from: https://my.clevelandclinic.org/health/diseases/22172-edwards-syndrome
  9. 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 Trisomy 18 (Edwards syndrome). AboutKidsHealth Canada. 2016 July 19. Available from: https://www.aboutkidshealth.ca/article?contentid=875&language=english
  10. Satgé D, Nishi M, Sirvent N, Vekemans M. A tumor profile in Edwards syndrome (trisomy 18). InAmerican Journal of Medical Genetics Part C: Seminars in Medical Genetics 2016 Sep (Vol. 172, No. 3, pp. 296-306).