Patau syndrome, also called Trisomy 13, is a chromosomal condition associated with severe intellectual disability and physical abnormalities in many parts of the body. Individuals with trisomy 13 often have heart defects, brain or spinal cord abnormalities. Due to the presence of several life-threatening medical problems, many infants with trisomy 13 die within their first days or weeks of life.
Patau syndrome is the least common and most severe of the viable autosomal trisomies. Median survival is fewer than 3 days. Only five percent to 10 percent of children with this condition live past their first year.
Patau syndrome occurs in about 1 in 16,000 newborns. Although women of any age can have a child with trisomy 13, the chance of having a child with this condition increases as a woman gets older.
Newborns born with Patau syndrome often have physical abnormalities or intellectual issues.
Other symptoms include:
• Extra fingers or toes (polydactyly)
• Deformed feet, known as rocker-bottom feet
• Neurological problems such as a small head (microcephaly), failure of the brain to divide into halves during gestation (holoprosencephaly), severe mental deficiency
• Micrognathia or smaller lower jaw size than normal
• Cutis Aplasia or missing skin on the scalp
• Deformation of ears accompanied with deafness
• Microphthalmia or poorly developed eyes
• Facial defects such as small eyes (microphthalmia), absent or malformed nose, cleft lip and/or cleft palate
• Hernias such as umbilical hernia or inguinal hernia
• Heart defects (80 percent of individuals)
• Kidney defects
• Undescended testes
When a baby is conceived, a normal egg cell and normal sperm cell start with 46 chromosomes. The egg and sperm cells then divide in half. The egg and sperm cells then have 23 chromosomes each. When a sperm with 23 chromosomes fertilizes an egg with 23 chromosomes, the baby will then have a complete set of 46 chromosomes. Half are from the father and half are from the mother.
But sometimes an error occurs when the 46 chromosomes are being divided in half. An egg or sperm cell may keep both copies of chromosome number 13, instead of just 1 copy. If this egg or sperm is fertilized, then the baby will have 3 copies of chromosome number 13. If the baby has 3 copies of chromosome number 13, this is called Patau syndrome or trisomy 13.
Risk Factors –
When a couple has a baby with Trisomy 13, it is usually unexpected. Nevertheless, some risk factors exist.
• The chance of having a baby with Trisomy 13 is higher in older mothers.
• Trisomy 13 can be inherited due to a familial chromosome rearrangement called a translocation.
Trisomy 13 is never the result of anything a mother or father did, or didn’t do.
• Full Trisomy 13
The existence of a third copy of chromosome 13 in all of the cells. About 95% of cases of Trisomy 13 are this type.
• Mosaic Trisomy 13
The existence of a third copy of chromosome 13 in some of the cells. About 5% of cases of Trisomy 13 are this type.
• Partial Trisomy 13
The existence of a part of a third copy of chromosome 13 in the cells. Less than 1% of cases of Trisomy 13 are this type.
Severe, often life-threatening health problems occur in trisomy 13. Treatment for complications varies depending on the body organ affected and the severity of the problem.
Trisomy 13 can be diagnosed while you are pregnant or after your baby is born.
• A cell-free DNA screening is a noninvasive blood test that can be done as early as 10 weeks into pregnancy. If your screen shows a positive result, it means that your child may have trisomy 13, but that more concrete testing is needed.
• An ultrasound scan may reveal certain features that match up with Patau syndrome, like extra fingers or toes, small head size, or eye abnormalities.
• Amniocentesis is a diagnostic test that can be done after week 15 of pregnancy. Your doctor will obtain a sample of amniotic fluid to look for additional chromosomes.
• Chorionic villus sampling is a test that can be done earlier than amniocentesis, at 10 to 13 weeks. Your doctor will obtain a sample of placental tissue to look for additional chromosomes.
After birth, your child’s doctor may make a diagnosis based on a physical exam, certain characteristics, and blood tests to analyze chromosomes.
There is no definitive treatment for Patau’s syndrome. As it cannot be cured, the treatment is usually based on the symptoms that ail the baby. The aim of the medical staff at the hospital is to minimize the discomfort of the baby and ensure that it is able to feed. Very often, the baby will be unable to respond to normal stimuli due to its abnormal development.
The care of the baby includes counseling the parents about what to expect. A support system is essential to help the new parents deal with the stark reality of the fact that their baby is not going to live beyond a year if it makes it past the first week in the hospital. It can be an emotionally traumatic experience for the parents.
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