Trisomy 13, also known as Patau syndrome, is a genetic condition in which cells in the body have three copies of chromosome 13 instead of two. The condition arises when errors occur during cell division and fertilization, where either the egg or sperm carries an additional copy of chromosome 13 and passes it on to the embryo. This extra chromosome disrupts the genetic balance, leading to a variety of symptoms and health complications, ranging from miscarriages and stillbirths to short life span and compromised life quality of affected individuals [1, 2]. Additionally, expectant parents may receive mixed messages from medical professionals regarding treatment interventions following a trisomy 13 diagnosis.
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History of trisomy 13
Initially described in 1656 as a case study by Thomas Bartholin, trisomy 13 was first reported in 1960 by Klaus Patau, his wife, Eeva Therman – also known as Mrs. X Chromosome for her extensive research into sex chromosomes – and by Smith, Inhorn, and Wagner [3]. In honor of the scientists who described it, the condition is also referred to as Bartholin-Patau, although it is most commonly called Patau syndrome.
How common is trisomy 13?
Estimates of the frequency of trisomy 13 vary from 1 in 5,000 births [4] to in 1 in 16,000 births [1]. The risk of having a baby with trisomy 13 increases with maternal age [1, 4], and the risk of trisomy 13 recurrence is around 1% [4]. This risk is higher only in cases where one of the parents unknowingly carries a balanced translocation, i.e. all genetic material is present but arranged incorrectly on the chromosomes [4].
Causes of trisomy 13
The majority of cases (75%) of Patau syndrome have free or standard trisomy 13, where there is an extra whole chromosome 13. Overall, 20% of cases are caused by translocations where an extra whole or partial chromosome is attached to another chromosome [4]. It is called partial trisomy 13 when part of an extra chromosome is found in cells [5]. In about 5% of cases, mosaic trisomy 13 is seen where some cells have three copies of chromosome 13, while other cells have two [4, 6]. Watch our team explain mosaicism here.
Due to the different causes of trisomy 13, symptoms can vary widely [1]. The individuals who survive longer are the ones with partial and mosaic trisomies, as symptoms are fewer and less severe [1, 4].
Symptoms of trisomy 13
Unfortunately, the most severe trisomy 13 cases – accounting for 95% overall – die in utero during early pregnancy [4, 7]. Of the babies with trisomy 13 carried to term, some are stillborn while others die within the first days or weeks of life [2]. A very small percentage (5-15%) survive past the first year of life [7].
Babies born with trisomy 13 may have low birth weight [7] and failure to thrive (gain weight) due to feeding difficulties [6]. Common symptoms include cleft lip and palate that occurs in up to 80%, congenital heart defects, such as atrial or ventricular septal defects in 80%, holoprosencephaly—a defect in the division of the brain into two halves—in 70%, and eye defects microphthalmia (small eyes) or anophthalmia (one or both eyes is missing) in 40% of cases. Additionally, they exhibit a wide range of symptoms including skeletal, kidney, vision, and hearing problems [4].
Other symptoms include [1, 2, 4, 5, 6]:
- Clenched hands
- Coloboma (missing tissue in eye)
- Ear dysplasia and deafness
- Extra fingers or toes
- Hernia
- Hypotonia
- Intellectual disability
- Microcephaly and micrognathia (small head and jaw)
- Omphalocele (abdominal organs develop outside of the body due to a defect in the abdominal wall)
- Kidney defects, including cysts
- Rounded bottom to the feet, known as rocker-bottom feet.
- Scalp defects (missing skin)
- Seizures
- Simian crease (single deep crease across the palms of the hands)
- Skeletal (limb) abnormalities
- Undescended testicle (cryptorchidism)
Diagnosing trisomy 13
Trisomy 13 can be detected prenatally through ultrasound, serum marker screening, and non-invasive prenatal testing (NIPT). NIPT has the highest detection accuracy and can be performed from the 10th week of pregnancy. Prenatal diagnosis is integral in trisomy 13 management, as it reduces postnatal diagnostic delays, and facilitates earlier and better decision-making by parents and physicians. Accurate information, and awareness of the condition and the spectrum of severity are instrumental for well-informed decision-making.
Treating trisomy 13
Unfortunately, trisomy 13 cannot be prevented and there is no cure; however, corrective surgeries and comfort measures may be beneficial in some cases [8]. Very few babies with trisomy 13 survive, and mortality rates may have been affected by historical guidelines that suggested terminating resuscitation efforts in some cases of major chromosomal abnormality such as trisomy 13 [9], leading to debate among healthcare professionals on how much medical intervention should be given to trisomy 13 infants. There is evidence that some babies with trisomy 13 (and 18) can survive surgical and other interventions, and the risks and benefits of medical intervention should be considered in each case [10].
Conclusion
Each patient with trisomy 13 is different, and their length of life is impossible to predict from the time of diagnosis as it depends on the level of medical care they will receive, and the severity of their symptoms. Importantly, change in attitudes and increased knowledge of trisomy 13 was influenced by support groups and families with affected children that spread awareness and demand medical care. Living with and caring for infants with trisomy 13 can be challenging, but knowledge can help prepare parents to come to terms with the diagnosis and decide on whether – and how much – medical intervention they would like; a decision that only they can make.
Read more about trisomies here.
References
[1] MedlinePlus [Internet]. Bethesda (MD): National Library of Medicine (US); [updated 2020 Jun 24]. Trisomy 13; updated 09 Sept. 2021; Available from: https://medlineplus.gov/genetics/condition/trisomy-13/. Accessed 24 Feb. 2025.
[2] National Health Service (2016) https://www.nhs.uk/conditions/pataus-syndrome/. Accessed 24 Feb. 2025.
[3] Patau K. et al. (1960) ‘Multiple congenital anomaly caused by an extra autosome’. Lancet. April 9;1(7128):790-3 https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(60)90676-0/fulltext
[4] Orphanet: Trisomy 13, https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=3378. Accessed 24 Feb. 2025.
[5] A.D.A.M. Medical Encyclopedia [Internet]. Johns Creek (GA): Ebix, Inc., A.D.A.M.; c1997-2020. Trisomy 13; [updated 18 Sept. 2023]. Available from: https://medlineplus.gov/ency/article/001660.htm. Accessed 24 Feb. 2025.
[6] NORD. “Trisomy 13 Syndrome – NORD (National Organization for Rare Disorders).” NORD (National Organization for Rare Disorders), NORD, 2015, https://rarediseases.org/rare-diseases/trisomy-13-syndrome/. Accessed 24 Feb. 2025.
[7] Peroos S. et al. (2012). ‘Longevity and Patau syndrome: what determines survival?’ BMJ case reports; December 6, 2012: bcr0620114381. https://casereports.bmj.com/content/2012/bcr-06-2011-4381.long
[8] International Health Alliance. “What Is Trisomy 13?” International Health Alliance, 5 Jan. 2021, www.internationaltrisomyalliance.com/what-is-trisomy-13/. Accessed 10 Mar. 2025.
[9] Morrison et al. (2010) ‘American Heart Association Guidelines for Cardiopulmonary resuscitation and emergency cardiovascular care. Part 3: Ethics’. Circulation, Volume 122, Issue 18. https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.110.970905
[10] Acharya, Krishna et al. “Medical and surgical interventions and outcomes for infants with trisomy 18 (T18) or trisomy 13 (T13) at children’s hospitals neonatal intensive care units (NICUs).” Journal of Perinatology: official journal of the California Perinatal Association vol. 41,7 (2021): 1745-1754. https://pmc.ncbi.nlm.nih.gov/articles/PMC8191443/
