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Trisomy 13 (Patau Syndrome)

Trisomy 13 (Patau Syndrome)



Overview

Trisomy 13 (Patau syndrome) is a rare genetic condition that occurs when the 13th chromosome appears three times (trisomy) instead of two times in a person’s DNA. Trisomy 13 affects the development of the face, brain and heart, along with physical growth abnormalities throughout a child’s body. Symptoms of trisomy 13 can be life-threatening and the condition poses a risk of miscarriage or death before the child turns 1 year old.

Who does trisomy 13 (Patau syndrome) affect?

Trisomy 13 can affect anyone because it’s the result of a copying error during fetal development where an extra chromosome joins a pair. The rate of occurrence is higher among children born to parents who are older than 35 years.

To understand your risk of having a child with a genetic condition, talk to your healthcare provider about genetic testing.

How common is trisomy 13 (Patau syndrome)?

Trisomy 13 occurs in an estimated 1 out of 10,000 to 20,000 live births. The mortality rate is high during a baby’s first few days of life and many pregnancies result in a miscarriage due to life-threatening symptoms like heart problems and spinal cord abnormalities during fetal development. Only 5% to 10% of babies born with trisomy 13 survive past their first year.

Symptoms

Symptoms of trisomy 13 affect several different parts of the body and range in severity for each person diagnosed with the condition. Symptoms of trisomy 13 include:

Heart abnormalities present at birth (congenital).

Physical growth irregularities with many cases targeting the spinal cord.

Severe issues with cognitive function.

Underdeveloped internal organs.

Physical symptoms

Physical symptoms of trisomy 13 include:

Cleft lip or cleft palate.

Difficulty gaining weight.

Extra fingers or toes (polydactyly).

Ears forming low on the head.

Growth abnormalities in the arms and legs.

Low muscle tone (hypotonia).

Small head and lower jaw.

Very small, close together or underdeveloped eyes.

Internal organ symptoms

Symptoms of trisomy 13 that affect the development of internal organs include:

Gastrointestinal (GI) problems that make eating difficult.

Heart failure.

Hearing problems.

Underdeveloped lungs.

Vision problems.

Since internal organ symptoms can be life-threatening, nearly 80% of babies diagnosed with Trisomy 13 don’t survive past their first year. Those that do survive may face more life-threatening complications after their first year including an increased risk of developing cancer and seizures.

Causes

A third chromosome 13 that attaches to a pair of chromosomes causes trisomy 13. A person with trisomy 13 has 47 total chromosomes.

There are normally 46 chromosomes in your body. Chromosomes carry DNA in cells, which works as an instruction manual to tell your body how to form and function. Genes are segments of your DNA that are chapters in your body’s instruction manual.

Cells initially form in reproductive organs by dividing from one fertilized cell, which is a combination of the sperm and the egg. The newer cells divide and copy themselves with half the amount of DNA as the original cell. During this process of cell division, a trisomy (when a third chromosome joins a pair) can occur randomly as cells re-type the instruction manual word for word. Any time that there’s a typo, symptoms of trisomy 13 occur because your cells don’t have the instructions they need to form and function properly.

There are three possible ways for a trisomy to form at chromosome 13 depending on how the chromosomes come together.

Complete trisomy 13

Random copying errors where more genetic material connects to a chromosome than necessary (complete trisomy 13) during the formation of the sperm and egg before conception causes trisomy 13. People with trisomy 13 have three copies of chromosome 13 instead of two. The extra genetic material attached to chromosome 13 causes symptoms of the condition.

Translocation

In about 20% of trisomy 13 cases, symptoms occur when part of chromosome 13 attaches to a nearby chromosome when eggs and sperm form (translocation) during fetal development. In this case, there are two pairs of chromosome 13, and an additional copy of chromosome 13 forms and bonds with a nearby chromosome pair, not necessarily in the 13th position.

Mosaic trisomy 13

In rare cases, an extra copy of chromosome 13 appears in some cells in the body but not all cells. This means that some cells in the body have three chromosome 13’s and others only have a pair of chromosome 13 (euploid). The severity of symptoms for a mosaic trisomy 13 diagnosis depends on how many cells have the third copy of trisomy 13. Symptoms are more severe if more cells have a third copy.

Diagnosis

During the first trimester of pregnancy, your healthcare provider may offer genetic testing in addition to prenatal ultrasounds, with tests as early as 11 to 14 weeks to check for genetic changes, like a third chromosome attached to a pair. Confirmation of the diagnosis occurs after your baby is born, when your healthcare provider can physically examine your baby for symptoms and provide additional tests, if necessary.

Your healthcare provider will offer screening tests during pregnancy to test a sample of your blood in addition to an ultrasound. During the ultrasound, your healthcare provider will look for signs of a trisomy, like excess amniotic fluid. The most common diagnostic test for trisomy 13 is a karyotype test.

Treatment

Trisomy 13 requires immediate and long-term treatment after your baby is born to alleviate any symptoms associated with the condition. Treatment for children born with trisomy includes:

Educational support.

Medicines to reduce symptoms.

Speech, behavioral and physical therapy.

Surgery to repair any physical abnormalities.

While some trisomy 13 cases can result in a live birth, severe symptoms of the condition can prevent your child from reaching their first birthday. Most often, a trisomy 13 diagnosis results in a miscarriage or loss of pregnancy. During this challenging time, reach out for support from your friends, family and healthcare provider to find comfort after a loss. Grief counseling or bereavement counseling helps individuals cope with the loss of a loved one.

Type of Doctor Department : A pediatric cardiologists and neurologists


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