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Patau syndrome
Also known as Trisomy 13 · 47,XX,+13 · 47,XY,+13
This condition typically causes significant developmental problems and serious health issues affecting many parts of the body. It is often identified at or before birth and affects around 1 in 10,000 to 16,000 live births.
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Overview
Patau syndrome, or Trisomy 13, is a genetic condition caused by the presence of an additional copy of chromosome 13 in an individual's cells. Chromosomes are structures within cells that hold our genes, providing instructions for how the body grows and functions. Usually, humans have 46 chromosomes in 23 pairs; however, individuals with Patau syndrome have three copies of chromosome 13 instead of the typical two [PMID:33671212].
This surplus genetic material leads to considerable health and developmental challenges. The condition can impact multiple organ systems, leading to a broad spectrum of physical characteristics and medical complications. Patau syndrome is considered rare, affecting approximately 1 in 10,000 to 16,000 live births in the UK.
Symptoms & clinical features
Individuals with Patau syndrome often present with a complex set of clinical features affecting various body parts. Common physical characteristics may include a notably small head (microcephaly), underdeveloped or small eyes (microphthalmia), a split upper lip and/or roof of the mouth (cleft lip and/or palate), and extra fingers or toes (polydactyly).
Internally, there can be serious issues with organ development. Heart defects are very common, often involving structural abnormalities. Brain abnormalities, kidney problems, and gastrointestinal system issues are also frequently observed. These health difficulties contribute to the severe nature of the syndrome.
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Affected organs
Patau syndrome impacts many organ systems due to the wide-ranging effects of the extra chromosome 13. The brain is often severely affected, leading to intellectual disability and structural malformations. The eyes can be underdeveloped, and hearing difficulties may be present.
Major organs such as the heart and kidneys frequently show congenital defects. The skeleton can also be affected, leading to conditions like polydactyly. Gastrointestinal issues, including problems with the gut's rotation and function, may also occur. These widespread effects underscore the severity of the condition.
Risks & severity
Patau syndrome is a severe condition, and many affected pregnancies do not progress to term. For those born with Patau syndrome, the prognosis is often challenging. Most infants with the condition have a very short lifespan [PMID:33671212]. A small number of children may survive into childhood, but they generally experience significant medical complications and severe developmental delay.
While the exact prevalence is not well established across all populations, it is generally estimated to occur in about 1 in 10,000 to 16,000 live births. The severity of the condition means that early diagnosis and comprehensive supportive care are crucial.
Genetic causes
Patau syndrome arises from the presence of three rather than two copies of chromosome 13 in the body's cells. This chromosomal arrangement, called trisomy 13, represents the fundamental biological cause of the syndrome. Unlike conditions linked to alterations in single genes, Patau syndrome results from a whole extra chromosome affecting cellular function across multiple systems [PMID:33671212].
The additional chromosome 13 typically appears due to an error during cell division when egg or sperm cells form, a process known as nondisjunction. This random event means that all cells carry the extra chromosome. In less common scenarios, only certain cells may contain the extra chromosome (mosaicism), or a piece of chromosome 13 may attach to another chromosome (translocation). These variations can sometimes lead to different clinical presentations, though the core features of trisomy 13 remain consistent.
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Inheritance pattern
Patau syndrome is generally not inherited, particularly in cases of full Trisomy 13. It typically arises from a spontaneous event called 'nondisjunction' during the formation of reproductive cells (eggs or sperm). This means that the parents usually have a normal set of chromosomes.
In rare cases, if a parent carries a 'balanced translocation' involving chromosome 13, there can be an increased chance of having a child with Patau syndrome. However, individuals with balanced translocations usually do not have any health problems themselves.
Diagnosis & testing
Patau syndrome can often be suspected during pregnancy through prenatal screening tests, such as ultrasound scans which may show certain physical anomalies. If screening suggests an increased risk, diagnostic tests like chorionic villus sampling (CVS) or amniocentesis can confirm the diagnosis by analysing foetal cells for the extra chromosome 13 [PMID:33671212].
Following birth, a diagnosis can be confirmed through a blood test. This involves a 'karyotype' analysis to examine the chromosomes. The NHS Genomic Medicine Service (GMS) provides pathways for genetic testing for suspected chromosomal conditions under relevant R-codes following referral by a clinician, such as a paediatrician or geneticist.
Management & lifestyle
Due to the severe and complex nature of Patau syndrome, management focuses primarily on supportive care to address the specific symptoms and improve the quality of life for affected individuals and their families. This often involves a multidisciplinary team of healthcare professionals, including paediatricians, cardiologists, neurologists, and genetic counsellors.
Treatment plans are highly individualised and may include interventions for heart defects, feeding difficulties, and other medical complications. Families receive support from the NHS and specialist charities, with access to genetic counselling providing information and guidance on the condition and its implications.
UK care pathway
In the UK, individuals and families affected by Patau syndrome are supported through the NHS Genomic Medicine Service. If Patau syndrome is suspected, a referral to clinical genetics services is typically made. Genetic counsellors play a crucial role in explaining the condition, its inheritance, and available resources. Diagnostic testing for chromosomal anomalies, including trisomy 13, falls under specific NHS R-codes and is accessible through specialist genomic laboratories.
Frequently asked questions
What is the difference between Patau syndrome and other trisomies?
Patau syndrome is caused by an extra copy of chromosome 13. Other trisomies, like Down syndrome (Trisomy 21) or Edwards syndrome (Trisomy 18), involve extra copies of different chromosomes, each leading to a distinct set of medical issues and developmental challenges.
Is Patau syndrome inherited from parents?
In most cases, Patau syndrome is not inherited. It usually results from a random error during the formation of egg or sperm cells. Rarely, it can be linked to a parent carrying a 'balanced translocation', which increases the chance of having a child with the condition.
Can Patau syndrome be detected before birth?
Yes, Patau syndrome can often be detected during pregnancy. Prenatal screening tests, such as ultrasound scans, may indicate potential issues, which can then be confirmed by diagnostic tests like chorionic villus sampling (CVS) or amniocentesis.
What kind of support is available for families in the UK?
Families in the UK can access support through the NHS, including specialist care from paediatricians, geneticists, and genetic counsellors. Various charities also provide resources, information, and emotional support for families affected by Patau syndrome.
What is a 'karyotype' and how does it help diagnose Patau syndrome?
A karyotype is a test that examines an individual's chromosomes. For Patau syndrome, it would identify the presence of three copies of chromosome 13 instead of the usual two, confirming the diagnosis.
References
- Williams GM, Brady R. Patau Syndrome (Archived). 2023. PMID: 30855930
- Pereira EM. Trisomy 13. Pediatrics in review. 2023. PMID: 36587017
- Goel N, Morris JK, Tucker D. Trisomy 13 and 18-Prevalence and mortality-A multi-registry population based analysis. American journal of medical genetics. Part A. 2019. PMID: 31566869
- Cammarata-Scalisi F, Araque D, Ramírez R. Trisomy 13 mosaicism. Boletin medico del Hospital Infantil de Mexico. 2019. PMID: 31536039
- Siddik AB, Daley SF. Trisomy 13 (Patau Syndrome). 2026. PMID: 32644517
- Cohen MM Jr, Gorlin RJ. Pseudo-trisomy 13 syndrome. American journal of medical genetics. 1991. PMID: 1867286
- Satgé D, Nishi M, Sirvent N. A tumor profile in Patau syndrome (trisomy 13). American journal of medical genetics. Part A. 2017. PMID: 28544599
- Zhegalova IV, Vasiluev PA, Flyamer IM. Trisomies Reorganize Human 3D Genome. International journal of molecular sciences. 2023. PMID: 38003233