Patau Syndrome (Trisomy 13): Causes, Symptoms, Diagnosis, Treatment and Life Expectancy

Patau syndrome, also known as trisomy 13, is a rare chromosomal condition caused by an extra copy of chromosome 13 in some or all of a baby’s cells. Because chromosomes carry the genetic instructions needed for growth and development, having extra chromosome 13 material can affect many parts of the body, particularly the brain, heart, face, kidneys and other organs.

It is a serious condition, and many pregnancies affected by trisomy 13 end in miscarriage or stillbirth. Babies who are born alive often have complex medical needs, and most do not survive beyond the first year. However, survival varies considerably. Some children with mosaic or partial trisomy 13 live much longer than expected.

Receiving a prenatal diagnosis can be overwhelming for parents. Understanding what the diagnosis means, how it is confirmed and what treatment and supportive options are available can help families make informed decisions with their medical team.

What is Patau syndrome?

Patau syndrome is a genetic disorder in which there is an extra copy of chromosome 13. Normally, human cells contain 46 chromosomes arranged in 23 pairs. In classic or “full” trisomy 13, there are three copies of chromosome 13 rather than two, giving the cells 47 chromosomes.

There are three main forms:

• Complete trisomy 13: An extra chromosome 13 is present in essentially all cells.
• Mosaic trisomy 13: Only some cells have the extra chromosome.
• Partial trisomy 13: Only part of chromosome 13 is present in three copies, often because of a chromosomal translocation.

The type and amount of extra chromosome 13 material can influence how severely a baby is affected. Mosaic and partial forms may sometimes be associated with less severe features and longer survival.

What causes trisomy 13?

Patau syndrome usually happens because of an error during cell division called nondisjunction. This causes an egg or sperm cell to receive an abnormal number of chromosomes. After fertilisation, the resulting embryo can therefore have an extra chromosome 13.

Most cases happen randomly and are not caused by anything the parents did before or during pregnancy.

In a smaller number of cases, trisomy 13 is related to a Robertsonian translocation involving chromosome 13. A parent may carry a balanced translocation without having symptoms but can have an increased chance of having a pregnancy affected by an unbalanced chromosome arrangement.

Does Patau syndrome occur in meiosis 1 or 2?

It can occur during either meiosis I or meiosis II.

Research suggests that most complete trisomy 13 cases are caused by errors in the mother’s egg formation. One molecular study found that more than 91% of extra chromosome 13 copies were maternal in origin, with errors occurring in both meiosis I and meiosis II. Another large study found an almost equal distribution between maternal meiosis I and meiosis II errors.

So, the simple answer is: trisomy 13 can result from nondisjunction during meiosis I or II, although maternal errors account for the large majority of cases.

Does trisomy 13 come from mom or dad?

Most cases of complete trisomy 13 originate from the mother’s egg, but the extra chromosome can occasionally come from the father.

Importantly, this does not mean a mother or father “caused” the condition. Nondisjunction is generally a random event during the formation of reproductive cells.

In translocation trisomy 13, however, a parent may carry a balanced chromosomal rearrangement. This is why chromosome testing of both parents may be recommended when a baby is found to have a translocation involving chromosome 13.

Symptoms and physical features of Patau syndrome

Trisomy 13 can affect several organ systems, so babies may have a combination of physical and developmental abnormalities.

Common features include:

• Low birth weight and poor growth before birth
• Small head size (microcephaly)
• Brain abnormalities, particularly holoprosencephaly
• Cleft lip and/or cleft palate
• Very small or underdeveloped eyes
• Closely spaced eyes
• Low-set or unusually shaped ears
• Extra fingers or toes (polydactyly)
• Low muscle tone
• Congenital heart defects
• Kidney abnormalities
• Abdominal wall defects such as an omphalocele
• Feeding difficulties
• Breathing problems
• Seizures
• Significant developmental and intellectual impairment

Not every baby will have all of these findings. The presentation can be particularly variable in mosaic and partial trisomy 13.

What do babies with trisomy 13 look like?

There is no single appearance that every baby with Patau syndrome has. Some babies may have a small head, closely spaced or unusually small eyes, a cleft lip or palate, low-set ears, an unusual nose or facial structure, and extra fingers or toes.

Some may also have an omphalocele, in which abdominal organs protrude through an opening in the abdominal wall.

However, physical appearance alone cannot diagnose trisomy 13. A baby may have only a few noticeable physical features, particularly with mosaic or partial trisomy 13. Chromosome testing is needed to establish the diagnosis.

Can a trisomy 13 baby look normal?

Yes, particularly in some cases of mosaic or partial trisomy 13.

A baby with complete trisomy 13 is more likely to have multiple recognisable abnormalities. However, the severity can vary greatly, and some babies may not have obvious external features at birth.

This is one reason genetic testing is important. A normal-looking baby cannot be assumed to have normal chromosomes based solely on appearance.

What are the ultrasound signs of trisomy 13?

Prenatal ultrasound may identify several abnormalities that raise suspicion for Patau syndrome. Possible ultrasound findings include:

• Growth restriction
• Holoprosencephaly
• Abnormal facial development
• Cleft lip or palate
• Microcephaly
• Severe congenital heart defects
• Omphalocele or another abdominal wall defect
• Kidney abnormalities
• Polydactyly
• Abnormal limbs or feet
• Certain brain abnormalities

Importantly, ultrasound is a screening and diagnostic-support tool, not a chromosome test. Some affected pregnancies may have fewer detectable abnormalities, especially earlier in pregnancy or in milder forms.

How is Patau syndrome diagnosed?

Patau syndrome can be suspected during pregnancy through ultrasound and prenatal genetic screening.

Screening options include:

Cell-free DNA or NIPT: This blood test can screen for trisomy 13 from around 10 weeks of pregnancy. It is highly effective as a screening test but is not a definitive diagnosis.

Ultrasound: A first-trimester or detailed anatomy ultrasound may identify abnormalities associated with trisomy 13.

CVS: Chorionic villus sampling obtains placental tissue for chromosome analysis and can provide a prenatal diagnostic result.

Amniocentesis: A sample of amniotic fluid is examined for fetal chromosomes and is another diagnostic test.

After birth, doctors may use a karyotype, chromosomal microarray, or other chromosome analysis to confirm the diagnosis and determine whether the condition is complete, mosaic or related to a translocation.

How do you confirm trisomy 13?

The most reliable way to confirm trisomy 13 is diagnostic chromosome testing.

A positive NIPT or an ultrasound showing several abnormalities does not, by itself, prove that a baby has trisomy 13. A positive screening result is generally followed by genetic counselling and diagnostic testing such as CVS or amniocentesis.

After birth, a blood sample can be tested to identify the extra chromosome 13 and determine its pattern.

Can a trisomy 13 diagnosis be wrong?

A screening result can be wrong, although definitive diagnostic testing is much more reliable.

For example, NIPT analyses DNA fragments mainly originating from the placenta. A positive result indicates a high likelihood of trisomy 13 but does not prove that the fetus has the condition. False-positive and false-negative results can occur.

Therefore, when NIPT suggests trisomy 13, doctors generally recommend genetic counselling, detailed ultrasound assessment and diagnostic testing with CVS or amniocentesis.

Do most trisomy 13 babies miscarry?

Many pregnancies affected by trisomy 13 do not continue to term. Miscarriage and stillbirth are common because the chromosomal abnormality can cause severe problems with fetal development.

The exact proportion varies depending on how pregnancies are detected and whether the statistics include pregnancies diagnosed early through screening. Among babies born alive, more than 90% are reported to die during the first year in NHS guidance.

How long do babies with trisomy 13 live?

Life expectancy is usually short, but it varies from one baby to another.

Many babies with complete trisomy 13 die during pregnancy, shortly after birth or within the first weeks or months. More than 9 in 10 children born with Patau syndrome die during the first year, according to NHS information.

A smaller group survives beyond infancy. Children with mosaic or partial trisomy 13 may have a better chance of longer survival, although they can still have significant medical and developmental needs.

Therefore, there is no single answer to “How long can a child with trisomy 13 live?” Some die within days, while rare individuals have survived into adolescence or adulthood.

Why is trisomy 13 so fatal?

Trisomy 13 is life-threatening because the extra chromosome disrupts normal development of multiple organs.

Serious heart defects can interfere with circulation. Brain abnormalities can affect breathing, swallowing and neurological function. Underdeveloped lungs, feeding problems, aspiration, kidney abnormalities and severe neurological complications can also contribute to poor survival.

In newborns, cardiopulmonary arrest and central breathing disturbances are among the reported causes of death. Feeding difficulties and aspiration can also lead to serious deterioration.

Do babies with Patau syndrome suffer? Is trisomy 13 painful?

There is no way to say that every baby with trisomy 13 experiences pain in the same way.

Some babies may experience breathing difficulty, feeding problems, seizures, heart complications or other sources of discomfort. Others may have periods of relative comfort and stability.

When a baby has a life-limiting condition, doctors can provide comfort-focused or palliative care, including appropriate pain and symptom management. In other situations, families and medical teams may choose more intensive treatments. Decisions are individual and should focus on the baby’s condition, expected benefits and the family’s goals.

Is there a treatment for trisomy 13?

There is currently no treatment that removes the extra chromosome 13.

Treatment focuses on the baby’s individual medical needs. Depending on the situation, this may include:

• Respiratory support
• Feeding assistance
• Medicines for seizures
• Treatment of heart problems
• Surgery for selected structural abnormalities
• Physiotherapy and developmental support
• Hearing and vision care
• Palliative or comfort-focused care

Some babies may receive intensive medical treatment, while others may receive primarily supportive or palliative care. The appropriate approach depends on the child’s health, the severity of abnormalities and the family’s wishes.

What makes you high risk for trisomy 13?

The risk of having a pregnancy affected by trisomy 13 increases with maternal age, particularly as the mother gets older.

However, trisomy 13 can occur in pregnancies at any age. Other situations that may warrant genetic counselling include:

• A previous pregnancy affected by trisomy 13
• A parent carrying a balanced Robertsonian translocation involving chromosome 13
• Abnormal prenatal screening results
• Ultrasound findings suggestive of a chromosomal condition
• A family history of a chromosome rearrangement

If a translocation is identified in a baby, chromosome testing for both parents can help determine whether one parent carries a balanced rearrangement and clarify the risk in future pregnancies.

Can Patau syndrome be prevented?

In most cases, Patau syndrome cannot be prevented because it results from a random chromosome-separation error.

Parents should not blame themselves for a pregnancy affected by trisomy 13.

When a previous child or pregnancy has had translocation-related trisomy 13, however, genetic counselling can be particularly important. Testing can identify whether a parent carries a balanced chromosomal rearrangement and help determine reproductive options for future pregnancies.

Who is the longest living person with trisomy 13?

There is no reliable worldwide registry that can establish the current longest-living person with trisomy 13.

A frequently cited medical report published in 1981 described a 19-year-old girl with regular, non-mosaic trisomy 13, who was reported at that time as the oldest known living person with regular trisomy 13.

There have also been later reports of individuals surviving into adolescence and adulthood, including people with partial or mosaic forms. A 2007 case report described a 51-year-old woman with a partial translocation involving chromosome 13, illustrating just how variable survival can be in less typical forms of the condition.

These rare cases should not be interpreted as typical life expectancy for trisomy 13.

Frequently Asked Questions About Patau Syndrome

How long do babies with trisomy 13 live?

Most babies born with trisomy 13 do not survive beyond the first year. Many die during pregnancy, shortly after birth or during the first few months. A small number, particularly those with mosaic or partial trisomy 13, survive much longer.

What is Patau’s syndrome?

Patau syndrome is another name for trisomy 13, a chromosomal disorder caused by an extra copy or extra material from chromosome 13.

Does trisomy 13 occur in meiosis 1 or 2?

It can occur in either meiosis I or meiosis II. Studies show that most cases are maternal in origin, with both meiotic stages contributing to nondisjunction.

How is Patau syndrome diagnosed?

It can be suspected through ultrasound and prenatal screening such as NIPT. Confirmation requires diagnostic chromosome testing, usually through CVS or amniocentesis during pregnancy, or chromosome analysis after birth.

How do you confirm trisomy 13?

A karyotype or other diagnostic chromosome test confirms the presence of an extra chromosome 13. NIPT is a screening test and should not be considered definitive on its own.

Can a trisomy 13 baby look normal?

Yes. Babies with mosaic or partial trisomy 13 may have fewer or less obvious physical features. Genetic testing is needed for confirmation.

Why does trisomy 13 cause death?

The extra chromosome can severely disrupt development of the brain, heart, lungs, kidneys and other organs. Respiratory failure, cardiac complications, neurological problems, feeding difficulties and aspiration can contribute to death.

Do most trisomy 13 babies miscarry?

A large proportion of affected pregnancies end in miscarriage or stillbirth. Among live-born babies, survival during the first year remains low.

Can trisomy 13 be prevented?

Usually, no. Most cases occur randomly during chromosome division. Genetic counselling may help families understand recurrence risk when a translocation is involved.

Is trisomy 13 painful?

Trisomy 13 itself is not necessarily painful, but affected babies may develop medical problems that cause discomfort. Doctors can provide symptom relief and palliative care when appropriate.

What are the ultrasound signs of trisomy 13?

Important findings can include growth restriction, holoprosencephaly, heart defects, facial abnormalities, cleft lip or palate, omphalocele, kidney abnormalities and polydactyly.

Can a trisomy 13 diagnosis be wrong?

A screening result can be false-positive or false-negative. A positive NIPT should therefore be confirmed with diagnostic testing such as CVS or amniocentesis.

What is the treatment for Patau syndrome?

There is no cure for the underlying chromosome abnormality. Treatment is supportive and may include respiratory care, feeding support, medicines, surgery for selected defects and palliative care.

Final thoughts

Patau syndrome is a complex chromosomal condition with a wide range of possible effects. Although complete trisomy 13 is usually associated with severe abnormalities and a high risk of miscarriage, stillbirth and early death, the condition is not identical in every child. Mosaic and partial forms can sometimes have a substantially different course.

If a prenatal screening test or ultrasound has raised concerns about trisomy 13, it is important to remember that screening is not the same as diagnosis. A maternal-fetal medicine specialist, obstetrician and genetic counsellor can explain the findings and discuss diagnostic testing such as CVS or amniocentesis.

For families facing a confirmed diagnosis, medical care is only one part of the picture. Emotional support, genetic counselling and clear discussions about treatment goals and quality of life are equally important. The best care plan is one developed individually for the baby and family, with compassion, accurate information and shared decision-making.

To consult a Pediatrician at Sparsh Diagnostic Centre, call our helpline number 9830117733.

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