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

Medically Reviewed by Poonam Sachdev on October 18, 2023
Written by Stacey Jones, MS, BA, Kristin Mitchell
5 min read

Trisomy 13, sometimes called Patau syndrome, is a rare genetic condition that happens when babies have an extra 13th chromosome. 

Chromosomes in our cells carry DNA, which controls how our bodies develop. Usually, people have 23 pairs of chromosomes, half from each parent. 

But babies with trisomy 13 have three copies of chromosome 13 instead of two. This causes very serious physical and mental issues. If you're carrying a fetus with trisomy 13, a miscarriage is likely.

Most babies born with it don’t live past their first year, though some can survive much longer. This condition affects 1 in every 10,000 to 20,000 newborns. 

 

Trisomy 13 syndrome happens when cells don't divide normally while a fetus is forming. The extra chromosome can come from either the egg or the sperm.

Scientists think this happens by chance. The condition doesn't usually run in families. The risk goes up for parents over 35, but it could affect your pregnancy at any age. 

It can affect some of the body's cells, or all of them:

  • Full trisomy 13, the most common form, is when the extra chromosome is in all cells.
  • Mosaic trisomy 13 is when the extra chromosome is in some cells.
  • Partial trisomy 13 is when the baby inherits only part of the extra chromosome. 

Sometimes, chromosome 13 detaches from one cell and moves to another. This is known as translocation. This type has been linked to heredity.

 

The symptoms of trisomy 13 affect many body systems and parts. The more cells in your baby's body that have the extra chromosome, the more serious their symptoms will be.

Babies born with trisomy 13 tend to have a low birth weight and brain structure problems, which affect their facial development. About 80% of babies born with trisomy 13 have heart problems. Cleft lip or palate is also common.

Other physical symptoms include:

  • Eyes that are set close together
  • A nose or nostrils that aren't fully developed
  • Clenched hands 
  • Small eyes, head, or lower jaw
  • Low-set ears
  • Extra toes or fingers 
  • Low muscle tone
  • Missing skin on the scalp 
  • Hernias
  • A hole or split in the iris of the eye 
  • Palms with one crease instead of the usual three
  • Undescended testicle
  • An abnormal skeleton

Your doctor might notice physical signs of trisomy 13 during your regular first-trimester fetal ultrasounds.

If your fetus is at risk of having abnormal chromosomes, your doctor may do screening tests such as cell-free DNA screening (NIPT) or the PAPP-A (pregnancy-associated plasma protein A).

But these tests can’t tell your doctor whether your fetus definitely has trisomy 13. They can only show that it's more likely.

To make sure, your doctor will likely recommend a karyotype test, such as a chorionic villus sampling (CVS) or amniocentesis, the most common diagnostic test for trisomy 13. 

If you didn't have genetic testing during pregnancy, the diagnosis is confirmed after your baby is born, when the doctor can look at their symptoms. 

There's no cure for trisomy 13. Treatment depends on what kind of symptoms your child has. It might include:

  • Medications to ease symptoms
  • Physical, speech, or behavior therapy
  • Surgery for physical issues
  • Support with education

Depending on how serious the issues are, some parents and doctors may choose to wait on considering any treatment based on the chances of the baby’s survival. 

 

Complications from trisomy 13 start at birth. Most babies with the condition are born with heart disease. The extra 13th chromosome also causes other serious physical problems, such as:

Doctors can’t predict how long a baby with trisomy 13 might live if they don’t have any immediate life-threatening problems. 

More than 80% of babies with the condition don’t live past their first month, and only 5%-10% live past age 1. About 10% live more than 5 years.

Nutrition treatment and surgery can increase survival for babies with trisomy 13. But children with the condition rarely live into their teens.

Support from friends, family, and others who've been there can help you deal with the trauma that a diagnosis of trisomy 13 can bring. It may also help to learn more about the condition. Some places to start are:

  • SOFT (Support Organization for Trisomy 18, 13, and Related Disorders), a group that helps families affected by trisomy 13 share information and find referrals for care
  • Hope for Trisomy, which helps families connect with one another and find information and news about the condition.
  • UNIQUE (Understanding Rare Chromosome and Gene Disorders), an international organization dedicated to rare chromosome conditions like trisomy 13 that produces a newsletter and works to raise awareness about these diseases

Other organizations such as the National Organization for Rare Disorders (NORD) and the National Institutes of Health’s Genetic and Rare Diseases Information Center (GARD) have information and links to resources about trisomy 13 as well.

If your baby has trisomy 13, they may have serious mental and physical problems. It can be found in your first trimester of pregnancy. There's no cure for trisomy 13. But there are treatments, including surgery and therapy, that focus on easing symptoms and providing comfort to your baby.

Why is trisomy 13 so fatal?

Trisomy 13 disrupts a baby’s development in the womb. They grow slowly, are born severely underweight, and have many serious medical problems. That’s why trisomy 13 often results in miscarriage, stillbirth, or death soon after birth.

What age is the longest-living child with trisomy 13?

The longest-living person with trisomy 13 was recorded in a 1981 journal article as being 19 years old. How long your baby survives depends on their medical complications and what form of trisomy 13 they have. Despite the many challenges that face them, there are babies born with trisomy 13 who do progress. About 5%-10% of babies live past their first year.

Is trisomy 13 a type of Down syndrome?

No, but both are conditions in which three chromosomes are present instead of two. Down syndrome, also known medically as trisomy 21, affects the 21st chromosome.