What Causes Trisomy 13?

Trisomy 13 can be diagnosed through genetic testing

Ultrasound image of fetus with trisomy 13
Ultrasound image of fetus with trisomy 13. BSIP/Universal Images Group/Getty Images

Trisomy 13, also known as Patua syndrome, is a relatively rare chromosome abnormality that occurs in about 1 in 16,000 newborns. Those with the condition are born with severe intellectual and physical defects. Many infants with trisomy 13 are stillborn. Only five to 10 percent of those born with the condition will survive beyond their first year of life. The average life expectancy is three days. Stillbirths and miscarriages are common.

Trisomy 13 is caused by an extra copy of chromosome 13. Infants with trisomy 13 have 47 chromosomes instead of 46. Some people may have partial trisomy 13 in that part of chromosome 13 becomes attached to another chromosome. A small percentage of people may have mosaic trisomy 13, where only some cells have an extra chromosome 13. Children with mosaic trisomy 13 may have milder symptoms. 

Any woman can give birth to a child with Patua syndrome. However, the likelihood increases based on the mother's age –– with older mothers being more at risk.

Other conditions caused by trisomies –– three chromosomes instead of two –– include Down syndrome (trisomy 21) and Edwards syndrome (trisomy 18). Patua syndrome is the rarest of the three trisomies. 

Signs and Symptoms of Patua Syndrome

Signs of Patua syndrome are often present at birth. Newborns with trisomy 13 often exhibit the following symptoms:

  • Extra fingers or toes (polydactyly)
  • Deformed feet (known as rocker-bottom feet)
  • Neurological problems
  • Smaller than average head size (microcephaly)
  • Brain fails to separate into two hemispheres (holoprosencephaly)
  • Intellectual disabilities
  • Facial defects such as small eyes (microphthalmia)
  • Absent or malformed nose
  • Cleft lip or cleft palate
  • Heart defects (80 percent of individuals)
  • Kidney problems
  • Delayed growth
  • Feeding and breathing difficulties
  • An opening in the abdomen (omphalocele) 
  • Scalp defects
  • Irritability

Trisomy 13 symptoms may be confused with those of Edwards syndrome. Genetic testing can differentiate between the two conditions. 

Diagnosing Trisomy 13

Trisomy 13 can be diagnosed during pregnancy through prenatal testing. Expectant mothers with an increased risk chromosomal abnormalities. can choose to undergo an amniocentesis or chorionic villus sampling. If trisomy 13 is confirmed, a doctor can help you determine how to proceed with your pregnancy.

Genetic testing after birth can be done as well. If a child is born with Patua syndrome, they should have imaging tests to check for heart and brain abnormalities, as well as other organ defects. Poor neurological function can also help form a diagnosis. There is no cure nor are there any specific treatments for trisomy 13. If a child is born with the condition, medication and assistive therapies can help manage symptoms and any complications that may arise. 

If your child is born with Patua syndrome, a genetic counselor can advise you of your risks of having another child with the condition. 

Families affected by trisomy 13 can join the support group for Trisomy 13, called S.O.F. T. -- Support Organization for Trisomy.

Related Resources

Myths, Misconceptions and Facts about Down Syndrome

Trisomy 18 - Edwards Syndrome

Prenatal Testing for Down Syndrome

Should You Do Prenatal Testing?

Maternal Age, Chromosomes, and Down Syndrome


Patau Syndrome. Medscape. (2015) 

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