What Is Trisomy 13?

When a couple expects their baby, the main priority would be maintaining the baby’s health. However, rare genetic disorders like trisomy 13, also called Patau’s syndrome, disrupt these expectations. Trisomy 13 is a rare genetic disorder characterised by an abnormality in the number of chromosomes 13.¹ Understanding trisomy 13 is crucial due to its rarity. Therefore, this article aims to provide the symptoms and features of trisomy 13 in a baby. 

Genetics

Genes form the essential code for all living beings, shaping the physical traits of a person. Even a small change in a person’s genetics can have significant effects on physicality and health. We’ll explore chromosomes, genetic disorders, and how genetic testing works to detect trisomy 13.

Chromosomes

Every human cell has 23 pairs of chromosomes, and half of the chromosome is inherited from our mother and the other half from our father. Chromosomes carry our DNA, which acts as life’s blueprint, defining all our unique traits. Genes, functioning as precise instructions, direct the body’s growth, development, functions, and responses to the environment. Each gene contributes to a different function within the body.  

Genetic disorder

Genes aim to tailor every little detail in our bodies, but sometimes errors happen. In the case of trisomy 13, there are three copies of chromosome 13 present instead of the usual two. In the United Kingdom, trisomy affects approximately 2 out of every 10,000 births.²

Genetic testing

Genetic testing during pregnancy is not mandatory. However, healthcare providers often offer genetic testing to pregnant women, especially in higher-risk pregnancies, due to factors such as age and family history of genetic disorders. These tests provide valuable information about the baby’s genetic health and can help parents make informed decisions about their pregnancy. 

Follow-up tests, such as amniocentesis and chorionic villus sampling (CVS), are conducted to evaluate possible genetic abnormalities, including conditions like trisomy 13. These tests offer detailed information on the genes of the baby to guide medical decisions.

Amniocentesis

Amniocentesis is a medical procedure where a small amount of amniotic fluid, which surrounds the foetus in the womb, is extracted using a thin needle. This procedure is typically performed between the 14th and 20th weeks of pregnancy.³

 The extracted amniotic fluid contains cells from the baby, including genetic material. By analysing these cells, genetic abnormalities, including trisomy 13, can be detected through karyotyping, a technique that allows the visualisation of the baby’s chromosomes. It is a way for scientists to look at all the chromosomes in a cell. They arrange the chromosomes by size and other characteristics to see if there are any extra, missing, or abnormal chromosomes.

Chorionic villus sampling  

CVS involves the extraction of a tiny piece of placental tissue called chorionic villi, which shares the same genetic makeup as the fetus. This procedure can be performed between the 10th and 13th weeks of pregnancy.⁴ The extracted tissue is then analysed to identify any chromosomal abnormalities, including Trisomy 13. 

Trisomy 13

In medical genetics, the term “trisomy” refers to a condition with an extra copy of a specific chromosome. In the case of trisomy 13, it means there are three copies of chromosome 13 instead of the typical two. The prefix “tri-” indicates three, emphasising the presence of this additional chromosome. 

Trisomy 13 syndrome, also known as Patau’s syndrome, was named after researcher Patau K, who identified its origin in 1960.⁵ It seems to occur more often in females than males, and it is observed in approximately one in 5,000 to 12,000 live births.⁵ Having discussed trisomy 13 as a genetic disorder, we will now explore its diagnosis, beginning with its symptoms, followed by understanding how it is approached and managed.

Types of trisomy 13

1. Full trisomy 13

 In this type, every cell in the body has three copies of chromosome 13 instead of the usual two. This condition typically leads to more severe symptoms and health complications.

2. Mosaic trisomy 13

Mosaic trisomy 13 is characterised by the presence of a mixture of cells with the normal chromosome 13 count (two copies) and cells with an extra chromosome 13 (three copies). 

Both types of trisomy 13 result from errors during cell division, where chromosomes do not separate properly. These abnormalities can occur randomly and are not usually inherited. The severity of the disorder depends on the specific genetic makeup of the affected individual.

Symptoms

Trisomy 13 can impact a child’s developmental process, potentially resulting in physical growth irregularities such as:⁶

• Cleft palate
• Additional fingers or toes 
• Weak muscle tone
• Small head

This condition also influences the formation of internal organs, possibly causing severe, life-threatening symptoms such as:⁶

• Cardiac failure
• Auditory impairments 
• Underdeveloped respiratory system
• Visual complications.

Healthcare professionals will provide essential medical support tailored to specific symptoms of trisomy 13 to increase your baby’s chances of survival.

Life expectancy

Life expectancy in trisomy 13 varies significantly based on the severity of symptoms and overall health. Unfortunately, many infants born with trisomy 13 have a short lifespan, often due to serious medical complications associated with the condition.

Miscarriage

About 70% of pregnancies identified with Patau’s syndrome through screening tests result in either miscarriage or stillbirth.² While the risk of miscarriage decreases as the pregnancy advances, there remains a possibility of stillbirth.²

Survival rate

Over 90% of infants born with Patau’s syndrome do not survive beyond their first year.⁷ Approximately 10% of babies with milder variations of the syndrome, like partial or mosaic trisomy 13, live past their first year of life.⁷

Is trisomy 13 genetically inherited?

Trisomy 13, or Patau syndrome, is typically not inherited. It occurs due to a random error in cell division during the formation of the egg or sperm. This error results in an extra copy of chromosome 13 in each cell, leading to the condition. While extremely rare, in some cases, Trisomy 13 can be inherited if one of the parents carries a balanced translocation involving chromosome 13.⁸ However, the vast majority of Trisomy 13 cases occur sporadically, without any family history of the condition.

Frequently asked questions

Can trisomy 13 be prevented?

Trisomy 13 cannot be prevented as it arises from a random genetic mistake. The likelihood of having a child with a genetic disorder rises for mothers who are 35 years old or older during pregnancy.

What support is available for families affected by patau’s syndrome?

Families can find support through genetic counselling, support groups and consultation with specialised medical professionals experienced in dealing with genetic disorders. These resources can provide valuable information, emotional support, and guidance for families navigating the challenges associated with Patau’s syndrome.

Are there any treatments available for patau’s syndrome? 

While there is no cure for Patau’s syndrome, supportive care and interventions can help manage symptoms and improve the quality of life. This may include surgeries to fix physical abnormalities and therapies to support development.

Is there any trisomy disorder similar to patau’s syndrome?

Yes, there are other genetic disorders similar to trisomy 13, such as trisomy 18 (Edwards syndrome) and trisomy 21 (Down syndrome). These conditions also involve extra copies of specific chromosomes and can result in developmental and health challenges. Each disorder has distinct characteristics and varying degrees of severity. Genetic counselling and medical professionals can provide detailed information about these conditions.

How fatal are trisomy disorders?

Similar trisomy disorders, such as trisomy 18 (Edwards syndrome) and trisomy 13 (Patau syndrome), often have a high mortality rate, especially in the early stages of life. These conditions can lead to severe health complications, making the affected individuals vulnerable.

However, the severity of the condition varies widely, and some infants with these disorders can live longer with the help of advanced medical care and supportive interventions. Medical professionals can provide detailed information based on individual cases.

What Is a cleft palate? 

A cleft palate is a birth defect where a baby is born with a split or opening in the roof of the mouth. This opening can occur on one or both sides of the palate, making it difficult for the baby to eat, speak, and even breathe properly. Cleft palates are usually repaired with surgery.

Summary

Genetic disorders can cause unexpected changes, often showing up without warning. Trisomy 13 is a rare genetic disorder that is caused by having an extra copy of chromosome 13 instead of the usual pair. Trisomy 13 is usually diagnosed during the 14th to 20th week of pregnancy by genetic testing methods to look at chromosomes the fetus possesses and ultrasound to visualise the fetus’ physical appearance. Genetic testing can give detailed information for the accurate diagnosis of trisomy 13 and better prepare parents and healthcare professionals to provide adequate medical intervention. 

Understanding the symptoms (both physical and internal) of trisomy 13 can help parents decide the right course of action for their infant. Even though trisomy 13 cannot be prevented, genetic testing helps diagnose them accurately. Emotional support from community groups and experts makes a big difference, helping families navigate these challenges with strength and understanding.