Trisomy 13 is a chromosomal disorder caused by an extra chromosome 13 that results in severe intellectual disability and physical abnormalities.
Trisomy 13 is caused by an extra chromosome 13.
Infants are typically small and often have major brain, eye, face, and heart defects.
Tests can be done before or after birth to confirm the diagnosis.
There is no cure for trisomy 13, but some specific symptoms and complications caused by the syndrome can be treated.
(See also Overview of Chromosome and Gene Disorders.)
Chromosomes are structures within cells that contain DNA and many genes. Genes are segments of deoxyribonucleic acid (DNA) and contain the code for a specific protein that functions in one or more types of cells in the body. Genes contain instructions that determine how the body is supposed to look and function. (See Genes and Chromosomes for a discussion about genetics.)
An extra chromosome, making 3 of the same chromosome (instead of the usual 2), is called trisomy. Children who have trisomy 13 have a third chromosome 13.
Trisomy 13 occurs in about 2 out of 10,000 pregnancies. The extra chromosome usually comes from the mother. The risk of trisomy 13 increases with the mother's age.
For most affected infants, trisomy 13 is fatal soon after birth. About 10% of infants survive beyond the first year of life.
Symptoms of Trisomy 13
In the womb, affected fetuses are typically not very active. The amount of amniotic fluid may be too much or too little.
Physical abnormalities
At birth, newborns are usually small. The brain typically does not develop properly, and these children have many facial abnormalities such as cleft lip and cleft palate, small eyes, defects of the iris (the colored area of the eye), and underdeveloped retinas (the clear, light-sensitive structures at the back of the eyes).
The ears are abnormally shaped and usually low-set. Defects in the scalp and openings in the skin are common. Loose folds of skin often are present over the back of the neck.
Newborns commonly have a single crease in the palm, extra fingers and toes (polydactyly), and poorly developed fingernails.
Cleft Lip and Cleft Palate: Defects of the Face
Other abnormalities
About 80% of newborns have severe heart defects. A defect called ventricular septal defect, in which there is an abnormal opening between the right and left ventricles, is common. Sometimes the heart may be located on the right side of the chest instead of the usual placement on the left side (a condition called dextrocardia).
Undescended testes and an abnormal scrotum occur in boys. An abnormally formed uterus occurs in girls.
Newborns frequently have prolonged periods of no breathing (apnea).
Hearing loss is common and is often suspected but can be difficult to confirm because these children are severely intellectually disabled.
Diagnosis of Trisomy 13
Before birth, ultrasound of the fetus or blood tests of the mother
Before birth, chorionic villus sampling, amniocentesis, or both
After birth, the appearance of the infant and blood tests of the infant
(See also Next-generation sequencing technologies.)
Before birth, trisomy 13 may be suspected based on findings detected during an ultrasound of the fetus. Doctors also can do a test to find deoxyribonucleic acid (DNA) from the fetus in the mother's blood and use this DNA to determine an increased risk of trisomy 13. This test is called noninvasive prenatal screening (NIPS) or cell-free fetal DNA analysis.
If doctors suspect trisomy 13 based on the results of these tests, they often confirm the diagnosis by doing chorionic villus sampling to obtain and test a small sample of the placenta, amniocentesis to obtain and test a sample of the fluid that surrounds the fetus (amniotic fluid), or both.
After birth, the infant's physical appearance may suggest the diagnosis of trisomy 13. To confirm the diagnosis, the infant's chromosomes are analyzed using a blood test.
Treatment of Trisomy 13
Support for the family
There is no cure for trisomy 13.
Children with trisomy 13 have severe developmental delay and disability. They should receive physical and speech therapies starting early. It is recommended that family members seek support.
Some children may receive surgical treatment for certain abnormalities resulting from trisomy 13, such as certain heart defects and cleft lip and cleft palate.
Prognosis for Trisomy 13
For most infants, trisomy 13 is fatal soon after birth.
However, some infants are alive at 1 year of age and beyond.
More Information
The following English-language resource may be useful. Please note that The Manual is not responsible for the content of this resource.
