Patau syndrome – what is trisomy 13?

Patau syndrome – causes and risk factors.

Patau syndrome is a syndrome of genetic defects associated with an extra third chromosome 13. couples. It occurs as a result of an error during the division of the Parents’ germ cells. Importantly, this happens regardless of external factors, so it cannot be prevented. Due to an abnormal amount of genetic material, numerous errors develop in the yet unborn child. Unfortunately, most patients die during fetal life or shortly after birth. This is because Patau syndrome is classified as a lethal (fatal) defect. 

There are 3 mechanisms leading to trisomy 13:

• Simple trisomy – is a situation in which there is an extra copy of chromosome 13 in all cells of the body. This abnormality occurs during meiosis and is related to the age of the mother.
• Unbalanced robertson translocation – in this case there is an extra copy of chromosome 13, which is attached to another pair of chromosomes. This situation is not related to the age of the parent.
• Mosaicism – is a circumstance in which not all cells of the body have an extra chromosome 13. Therefore, a certain percentage of cells in the body contain an extra copy of chromosome 13, and the rest do not. This type of error occurs during mitosis and is also not dependent on the age of the mother.

It is worth knowing that the risk of Patau syndrome also increases when the mother-to-be is over 35, which is why free prenatal tests are targeted, among other things. For women who have reached 35. year of life. However, the Polish Society of Gynecologists and Obstetricians recommends that they be performed for all pregnant women.

Patau syndrome – symptoms

Symptoms of Patau syndrome can vary between affected children. In some situations, the course of the disease is strongly pronounced, and sometimes it happens that the symptoms are much less severe, so that the survival period is longer. This is especially true when the child is a mosaic (i.e., only some cells have an extra chromosome, and others are normal).

Symptoms of Patau syndrome in children include:

• Cleft lip and palate,
• congenital heart defects,
• kidney defects,
• Finger Faults,
• holoprosencephaly, an undescended division of the forebrain that causes, among other things. cyclopia;
• brain malformations,
• Intellectual disability of a severe degree,
• low birth weight,
• umbilical hernia,
• neural tube defects,
• deafness,
• non-substitution of testicles,
• characteristic cavities on the scalp.

Patau syndrome – diagnosis in pregnancy

The doctor during the I. and II. Trimester performs a mandatory ultrasound. The ultrasound evaluates markers of genetic defects (mainly nuchal translucency and presence of nasal bone). Very often, this type of examination already shows the first characteristics of Patau syndrome (these include the aforementioned cleft lip and palate, ventricular septal defect in the heart or cystic kidney disease). The specialist may also order a double test, where, in addition to the ultrasound image, the concentration of
beta- HCG
 and 
PAPP-A protein
. When imaging and screening results suggest abnormalities, an invasive test (e.g., amniocentesis) is implemented, which makes it possible to analyze the baby’s karyotype and confirm or exclude a genetic defect syndrome, of which Patau syndrome is an example.

There is now a non-invasive prenatal test available on the market , the so-called “free fetal DNA test.
free fetal DNA testing
. It involves analyzing the fetal genetic material present in the mother’s blood. It is particularly recommended for women who have been calculated to have an intermediate risk of genetic defects during screening – that is, between 1:300 and 1:1000.

Children with Patau syndrome – can they be cured?

Patau syndrome is an extremely serious defect that unfortunately cannot be causally cured. Nevertheless, there are methods of hospitalization to keep the child alive for as long as possible. This is the so-called. Palliative therapy, for which various types of medications are used to improve the comfort of the young patient. The effects of this treatment depend on the severity of the disease.

In addition, surgery is sometimes required for a cleft lip or palate, as well as a heart defect, if one exists. Specialists also recommend physiotherapy, if the toddler’s condition allows it.

Trisomy 13. chromosome – prognosis

Apgar Scale parameters determined after birth are very low for most cases – they are usually 0-3 points. Due to the coexistence of multiple birth defects, a lot of children with Patau syndrome die within days or weeks of birth (an estimated 80%). About 90% of toddlers do not live past the first year of life, and only 5% reach the age of 5.

It is worth knowing that Patau syndrome contributes to a high degree of intellectual disability, seizures and developmental disorders, which are not only unpleasant for the patient, but also for his Parents. However, medicine describes isolated exceptions of patients who lived several years, communicated with their families and showed little developmental progress.

Patau syndrome – what about after birth?

Sometimes it happens that the pregnancy went flawlessly, and the gynecologist found no abnormalities on ultrasound, and yet the child at birth presents features associated with a possible genetic defect. In such a situation, genetic tests are performed to examine the newborn’s karyotype, which can confirm or rule out, among other things. Patau syndrome.

Parents who learn of their child’s birth defect syndrome should always be able to consult a geneticist and receive support and assistance from both prenatal hospice while still in pregnancy and postpartum hospice for children.

Patau syndrome and another pregnancy

After a child is diagnosed with Patau syndrome, many Parents are concerned about the risk of the defect reappearing during a subsequent pregnancy. Risk of trisomy of chromosome 13. increases with a woman’s age, but most cases are related to a spontaneous error during conception. These are known as the “spontaneous” cases. De novo, or non-inherited, mutations.

Often Parents of a child affected by Patau syndrome decide to perform cytogenetic testing for carrying a balanced translocation, which is one of the causes of Patau syndrome. Both the child and the Parents are examined in such a situation, so that an increased risk of repeating trisomy 13 in subsequent pregnancies can be determined.

FAQ

• Patau syndrome – symptoms

Symptoms that often manifest with Patau syndrome include. severe mental retardation, multiple heart defects (e.g., persistent ductus arteriosus or dextrocardia), nervous system problems, cleft iris and brain damage.

• What are the risk factors for giving birth to a toddler with Patau syndrome ?

The high risk of having a child with such a genetic defect is caused by, among other things. By carrying a balanced translocation (in the case of this abnormality there is no excess genetic material, so its carrier is healthy) spontaneous separation of homologous chromosomes (mother and father) and the age of the mother.

• Children with Patau syndrome – what is the prognosis?

Most babies with Patau syndrome die within the first few days of life. There are isolated cases that describe adults functioning with the condition.