Patau Syndrome (Trisomy 13)

What is Patau Syndrome (Trisomy 13)?

Patau syndrome is a rare genetic condition that happens when a baby has an extra copy of chromosome 13. Most people have 23 pairs of chromosomes in every cell. Babies with Patau syndrome have three copies of chromosome 13 instead of two. This extra genetic material disrupts normal development before and after birth.

The condition affects about 1 in 10,000 to 16,000 newborns. It causes serious physical and mental challenges. Many babies with Patau syndrome have heart defects, brain abnormalities, and problems with other organs. The condition is also called trisomy 13 because of the extra third chromosome.

Most cases of Patau syndrome are not inherited from parents. The extra chromosome typically happens by chance during the formation of eggs or sperm. Advanced maternal age increases the risk, especially for mothers over 35 years old. Understanding this condition helps families prepare and make informed decisions about prenatal care.

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Symptoms

Heart defects present at birth
Brain or spinal cord abnormalities
Extra fingers or toes
Cleft lip or cleft palate
Small or poorly developed eyes
Low birth weight and poor muscle tone
Severe developmental and intellectual delays
Seizures
Kidney problems
Feeding difficulties

Many babies with Patau syndrome show visible physical differences at birth. Some symptoms may not appear until after delivery. The severity varies from person to person, but most cases involve multiple organ systems.

Causes and risk factors

Patau syndrome is caused by having an extra copy of chromosome 13 in some or all body cells. This happens most often because of a random error during cell division when eggs or sperm are forming. The error is called nondisjunction, meaning the chromosomes do not separate properly. When a sperm or egg with the wrong number of chromosomes joins with a normal one, the baby ends up with three copies of chromosome 13.

The main risk factor is advanced maternal age, particularly over 35 years. Older mothers have a higher chance of eggs developing with chromosome errors. In rare cases, a parent may carry a rearranged form of chromosome 13 that can be passed to the baby. Most of the time, neither parent has any genetic abnormality and the condition happens by chance. Having one child with Patau syndrome does not significantly increase the risk for future pregnancies unless a parent carries a chromosome rearrangement.

How it's diagnosed

Patau syndrome is usually diagnosed during pregnancy or shortly after birth. Prenatal screening tests can detect signs of the condition. First trimester screening may show abnormal levels of certain proteins and hormones in the mother's blood. Ultrasound examinations may reveal physical abnormalities like heart defects or extra fingers. Lower than normal estriol levels in maternal blood can indicate Patau syndrome in an unborn baby.

If screening tests suggest a problem, doctors recommend diagnostic testing. Chorionic villus sampling or amniocentesis can confirm the diagnosis by examining the baby's chromosomes directly. These tests analyze cells from the placenta or amniotic fluid. After birth, doctors can diagnose Patau syndrome based on physical features and confirm it with a blood test called a karyotype. The karyotype shows the number and structure of all chromosomes. Talk to a doctor about specialized prenatal testing if you have concerns about genetic conditions.

Treatment options

Supportive care focused on managing symptoms and improving quality of life
Surgery to repair heart defects or cleft lip and palate when appropriate
Feeding support including special bottles or feeding tubes
Physical therapy to help with muscle tone and development
Medications to control seizures if they occur
Regular monitoring by a team of specialists including cardiologists and neurologists
Palliative care to ensure comfort and dignity
Family counseling and support services

Frequently asked questions

Most babies with Patau syndrome have a very limited life expectancy. About 50% of affected babies do not survive beyond the first week of life. Only 5 to 10% live past their first year. A small number of children with partial or mosaic forms of the condition may survive longer with intensive medical care.

Yes, Patau syndrome can often be detected during pregnancy. Prenatal screening tests in the first or second trimester may show warning signs. Ultrasound can reveal physical abnormalities. Diagnostic tests like amniocentesis or chorionic villus sampling can confirm the diagnosis by analyzing fetal chromosomes.

The extra chromosome usually happens by chance during the formation of eggs or sperm. A random error called nondisjunction causes chromosomes to divide incorrectly. This error is not caused by anything the parents did or did not do. Advanced maternal age is the main known risk factor.

Most cases of Patau syndrome are not inherited. The extra chromosome occurs randomly during reproduction. In rare cases, about 20% of the time, a parent carries a balanced translocation involving chromosome 13. This rearrangement can be passed to children and may increase the risk of having a baby with Patau syndrome.

Full trisomy 13 means every cell has an extra chromosome 13. Mosaic trisomy 13 means only some cells have the extra chromosome while others are normal. Mosaic forms usually cause less severe symptoms and may have a better prognosis. The extent of mosaicism varies from person to person.

Common heart defects include holes in the walls between heart chambers. These are called atrial septal defects or ventricular septal defects. Babies may also have patent ductus arteriosus, where a blood vessel that should close after birth remains open. Many babies have multiple heart abnormalities that affect blood flow and oxygen levels.

Prenatal screening is offered to all pregnant people, but it becomes more important with advancing maternal age. Women over 35 have a higher risk of chromosome abnormalities like Patau syndrome. Your doctor can discuss screening options and help you decide what tests are right for you based on your individual situation and preferences.

There is no known way to prevent the random chromosome errors that cause most cases of Patau syndrome. If a parent carries a chromosome translocation, genetic counseling can help assess the risk. Prenatal testing allows for early diagnosis and informed decision making. Folic acid and prenatal vitamins support healthy pregnancy but do not prevent chromosome abnormalities.

Babies with Patau syndrome need care from multiple specialists. This typically includes cardiologists for heart problems, neurologists for brain issues, and surgeons for physical defects. Many babies need help with feeding and breathing. The care team works with families to provide comfort care and address medical needs as they arise.

If the Patau syndrome occurred randomly, your risk for future pregnancies is about 1%. This is slightly higher than the general population risk. If genetic testing shows that you or your partner carries a chromosome translocation, the risk can be much higher. Genetic counseling can help you understand your specific situation and options for future pregnancies.