Trisomy 13, also referred to as Patau syndrome, is a rare genetic condition that occurs when a person has an extra copy of chromosome 13 in their cells. Our genetic information is contained in chromosomes, which determine how we develop and function. In normal circumstances, we have 23 pairs of chromosomes, one from each parent. However, in trisomy 13, chromosome 13 is duplicated three times instead of two. It affects the development of the face, brain, heart, and other organs in various ways.
The condition usually occurs by chance during the formation of an egg or sperm before conception, so the parents are not carriers and are not at greater risk of developing trisomy 13. In some cases, trisomy 13 can be inherited from a parent who has chromosome 13 rearrangement known as a translocation. The parent may not experience any symptoms of trisomy 13 since part of chromosome 13 is attached to another chromosome. The risk of having a child with trisomy 13 increases with the mother's age, especially after 35 years of age.
Trisomy 13 symptoms vary depending on how many cells have the extra chromosome 13 and which organs are affected. Some common symptoms include:
A small head (microcephaly) with an abnormal shape
A cleft lip and/or palate, which is an opening in the upper lip or roof of the mouth
Low-set ears that are malformed or missing
Eye defects, such as small or absent eyes (anophthalmia), or extra tissue in the eye (coloboma)
A single crease across the palm of the hand (simian crease)
Extra fingers or toes (polydactyly)
A small lower jaw (micrognathia)
A narrow forehead and a flat nose bridge
A scalp defect, such as a missing patch of skin or hair (cutis aplasia)
A low birth weight and slow growth
A low muscle tone (hypotonia) and poor reflexes
Severe intellectual disability and developmental delay
Seizures and brain abnormalities, such as a small or missing part of the brain (holoprosencephaly)
Heart defects, such as a hole in the heart (atrial septal defect or ventricular septal defect) or a narrowing of the main artery that carries blood from the heart to the body (coarctation of the aorta)
Kidney problems, such as cysts or missing kidneys (renal agenesis)
Hernias, which are bulges of organs through a weak spot in the abdominal wall
Skeletal abnormalities, such as a curved spine (scoliosis) or a short breastbone (pectus excavatum)
Trisomy 13 can be diagnosed before or after birth, depending on the availability and accuracy of the tests. Some of the tests that can be used to diagnose trisomy 13 include:
It is possible to determine the risk of having a baby with trisomy 13 based on the mother's age, the baby's size, and the presence of certain markers in the blood or on the baby's neck during prenatal screenings, which are blood tests and ultrasound scans. Neither of these tests is definitive, but only provides an indication of trisomy 13 probability.
Prenatal diagnostic tests, which are invasive tests that can confirm the diagnosis of trisomy 13 by analyzing the baby's chromosomes from a sample of amniotic fluid (amniocentesis) or placenta (chorionic villus sampling). While these tests are more accurate, they are also associated with a small risk of miscarriage or infection.
The postnatal test is used to diagnose trisomy 13 after the baby is born by examining the baby's physical features and taking a blood sample to analyze the chromosomes (karyotype).
There is no cure for trisomy 13, and the treatment is mainly supportive and palliative, which means that it aims to relieve the symptoms and improve the quality of life of the baby and the family. The treatment may include:
Surgery to correct some of the physical defects, such as the cleft lip and palate, the heart defects, or the hernias. However, surgery may not be recommended for some babies who have severe or multiple abnormalities and a poor prognosis.
Medications to control the seizures, infections, pain, or other complications that may arise from trisomy 13.
Feeding assistance, such as a feeding tube or a special bottle, to help the baby get enough nutrition and prevent choking or aspiration.
Physical therapy, occupational therapy, and speech therapy to help the baby develop their motor skills, sensory abilities, and communication skills.
Special education and early intervention services to help the baby learn and achieve their potential.
Counseling and support groups to help the parents and the siblings cope with the emotional and practical challenges of caring for a baby with trisomy 13.
In most cases, trisomy 13 is a random event that occurs during the formation of an egg or sperm. However, there are some steps you can take to reduce the chance of having a baby with trisomy 13:
Having a preconception checkup and taking folic acid supplements before and during pregnancy to ensure optimal health and prevent neural tube defects.
Having prenatal screening and diagnostic tests to detect trisomy 13 early and make informed decisions about the pregnancy and the baby’s care.
Seeking genetic counseling and testing if there is a family history of trisomy 13 or other chromosomal conditions to understand the risk and the options for future pregnancies.
