A normal human cell contains 46: 23 pairs of chromosomes One set of the 23 chromosomes originates from the biological father from sperm, while the other set comes from the mother’s egg. Each chromosome comprises thousands of genes, which form proteins needed by the body for chemical reactions, growth, and development.
However, sometimes, an individual can miss one chromosome or it can get turned upside-down, or switched, resulting in a chromosol abnormality. Trisomy 13 or Patau’s syndrome is one example of chromosol abnormality that affects unborn babies.
Here, we will discuss everything about this rare genetic disorder, from its cause to treatment.
What is Trisomy 13?
Trisomy 13 or Patau’s disease is a rare genetic condition that occurs when there’s an extra copy of chromosome 13 in one cell or all of them. The disorder was first described in 1960 by Patau, hence the name Patau’s disease.
It’s identified by other names, including Patau Syndrome, Bartholin-Patau Syndrome, and Complete trisomy 13 syndrome. Also, the syndrome occurs in about 1 in 20,000 newborns.
A normal kid usually has 2 copies of chromosome 13, but those born with Trisomy have 3 copies. This usually happens due to abnormal cell division during reproduction, which results in additional genetic materials of chromosome 13.
Both the egg from the mother and sperm from the father can produce the extra chromosome. But according to doctors, women aged 35 and above are more susceptible to giving birth to kids with this chromosol defect.
Trisomy 13 is often associated with server mental and physical disabilities. Unfortunately, this condition often results in miscarriage and stillbirth. Even if the child is born, he will have a low survival chance. In fact, 9 out of 10 kids born with the condition will not live past the first month or year. But some babies do manage to live for years.
Trisomy 13 occurs by chance and naturally. The third chromosome 13 develops in the cell randomly during conception, affecting the fetus’s development.
However, it can also result when the chromosome attaches itself (translocated) to another chromosome during the early stages of fetal development. This process is what we know as chromosol translocation.
In rare cases, sections of chromosome 13 can attach to other chromosomes, causing a condition called trisomy 13 mosaicism or mosaic.
The type of trisomy 13 determines the severity of the condition. Trisomy 13 mosaic is usually less severe compared to full Trisomy 13.
Trisomy 13 cannot be inherited; it occurs randomly during the first stages of reproduction. An error occurs, leading to nondisjunction cell division, which results in additional chromosome 13.
That said, it is possible to inherit translocation trisomy 13. A person can carry the additional chromosome 13 in form of re-arranged genetic material. The extra chromosome 13 arranges itself in other chromosomes, such that there’s no trace of it. Such a process is called a balanced translocation. The genetic material of the chromosome then gets passed down to the next generation.
Infants with Trisomy 13 usually have several health problems. First, they are born underweight since their growth is restricted in the womb. Also, most babies never develop a full brain structure (the brain never divides into 2 halves) and often suffer from heart problems.
Other health defects include:
- Microcephaly or small head
- Cleft lip or palate
- Microphthalmia–abnormally small eyes
- Hypotelorism – reduced distance between one eye to another
- Cutis Scalp–scalp missing skin
- Low-set ears or deafness
- Undescended testes
- Raised, red birthmarks
- Polydactyly–additional fingers and toes
- Absence of one eye or both
- Enlarged clitoris in girls
- Abnormal cysts in the kidneys
As we said earlier, most newborns with this condition don’t live for long. Those who survive have to deal with health issues, such as:
- Neurological problems
- Intellectual disabilities
- Slow growth
- Difficulties with breathing
- Slow growth
- Trouble digesting food or even eating
- Congenital heart defects
A doctor can spot symptoms of trisomy 13 during a clinical exam (first-trimester fetal ultrasounds). He will conduct a genetic test like pregnancy-associated plasma protein-A (PAPP-A) or cell-free DNA screening (NIPT) and others to check the chromosome karyotype. By checking the chromosome, the doctor can determine if a parent has translocation trisomy 13.
However, the mentioned tests are screening tests, meaning the doctor can’t tell for sure if the unborn baby has trisomy 13. They only alert the specialist of the possibility of the condition. There might be a need for additional tests like amniocentesis or chorionic villus sampling (CVS) for confirmation.
These are invasive tests that involve removing a sample of fluid or tissue for testing to see if there’s an extra chromosome 13. If the parents visit a private hospital, the specialist might conduct a non-invasive prenatal test, which involves removing a sample of the mother’s blood. The baby’s DNA found within the blood then gets tested for trisomy 13.
Besides screening, pregnant mothers get scanned to look for signs of physical abnormalities linked to Patau’s syndrome. The scan is often conducted between 18 and 21 weeks of pregnancy.
Other tests parents might undergo to determine if the unborn kid has trisomy 13 include maternal blood screening and fetal ultrasound.
Trisomy 13 has no specific cure. Treatment mainly focuses on symptom management and offering comfort as well as supportive care. However, the care depends on the specific symptoms displayed by the newborn.
To ensure the survival of the kid, doctors might have to perform surgery if the baby manages to survive the first months. But parents and doctors must evaluate whether to take extraordinary measures to prolong the baby’s life against the severity of mental and physiological issues present and the prospect of post-surgical recovery.
In some cases, Trisomy 13 is not life-threatening. But it’s hard for doctors to predict the lifespan of the newborn if he has no life-threatening defects. But even if a kid survives, chances are he won’t make it into teenhood.
Genetic Testing for Parents
If doctors discover translocation trisomy 13 in an unborn baby, the parents of the baby might have to get their chromosomes analyzed.
Genetic testing allows parents to better plan for future pregnancies, but not for the current pregnancy. The outcome of the test will allow doctors to determine the likelihood of the condition affecting future pregnancies.
Scientists are yet to find a way to prevent this rare chromosomal defect. Also, there’s no reason whatsoever to blame a parent for causing or failing to prevent trisomy 13 in their baby.
If you’re 35 years and older, you are at a high risk of giving birth to a kid with trisomy 13. But don’t worry! The chance of this happening is very low. Nevertheless, if you suspect your baby has the syndrome, it’s wise to contact a healthcare provider. This way, they can conduct tests to confirm if the kid has the defect. This will also help in determining the risk to future pregnancies.
The doctor might refer you to a genetic counselor, where you will get more information about the chromosol defect and tests available to diagnose the condition before giving birth.
That said, Trisomy 13 is a rare but severe genetic condition that impairs a kid’s intellectual and physical capacity. So, if you’re pregnant, you must visit a hospital and conduct various genetic tests to check if your kid has any chromosomal defect.