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Trisomy 13
Monday, 21 July 2003
Thursday, 14 July 2005
Patau Syndrome

What

Trisomy 13 is a chromosome abnormality caused by having three copies of chromosome 13. Normally, each person has two copies of every chromosome. One copy comes from the mother, and one copy comes from the father. Children with trisomy 13 have two copies of all their chromosomes and an extra copy of chromosome 13. It is also possible for a child to have an extra copy of only part of chromosome 13, which is called partial trisomy 13.

Who

Trisomy 13 occurs in all ethnicities and equally affects both males and females. Trisomy 13 occurs in about 1 in 10,000 live births.

Signs and Symptoms

Trisomy 13 is present from birth. Children with trisomy 13 have certain physical characteristics but may not have all of the following symptoms: 

  1. Infants have difficulties breathing and feeding.
  2. The head is small with a sloping forehead.
  3. They may have an opening in the lip or palate because it did not close or come together completely (called a cleft lip or cleft palate).
  4. The ears are placed lower on the head than normal.
  5. There can be hearing loss and recurrent ear infections.
  6. There can be abnormal or missing ribs.
  7. There may be extra fingers and toes.
  8. The eyes are often small or spaced closely together and there may be defects of the eyes.
  9. The brain may not be completely separated into two halves (into the left and right sides of the brain.)
  10. The infant may not breathe periodically (apnea).
  11. There may be seizures.
  12. The chin may be small.
  13. There may be heart problems.
  14. The back of the neck may have extra loose skin.
  15. They have severe mental retardation.

Possible Causes

Trisomy 13 is caused by having an extra copy of part or all of chromosome 13. Most commonly, the extra chromosome comes from the mother. In 75% of cases, trisomy 13 results because the chromosomes did not separate normally in the mother’s egg and the fetus receives two copies of chromosome 13 from the mother instead of just one copy (a process called non-disjunction). The risk of non-disjunction increases as mothers get older. Approximately 20% of cases are due to the joining of two chromosomes 13. This is referred to as a Robertsonian translocation. About 5% of cases are caused by the chromosomes not separating normally after fertilization.

Diagnosis

The diagnosis of trisomy 13 is made by the above signs and symptoms. Genetic testing to look at the chromosomes, called a karyotype, can confirm the diagnosis. This testing can be performed during the pregnancy (prenatally) using amniocentesis or chorionic villus sampling, or after the baby is born.

Treatment

There is currently no treatment or cure for trisomy 13. The infant should be kept comfortable.

Prognosis

The prognosis for infants with trisomy 13 is not very good. Approximately 45% of infants do not live past 1 month of age, 69% do not live past 6 months, and 72% do not live past 1 year. The prognosis is different for children with partial trisomy 13 depending on how much extra chromosome material there is.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

SOFT: Support Organization For Trisomy 18, 13 and Related Disorders 
A great website with information about Trisomy 13 as well as available support for families affected by the disorder.

HAND: Helping After Neonatal Death
A volunteer support group which helps families who have experienced loss of a baby before, during, or after birth.

Medline Plus
A well-written article on Trisomy 13 with nice definitions of medical terms.

Google Search for Trisomy 13

References and Sources

Jones KL (1996). Smith’s Recognizable Patterns of Human Malformation. 5th edition. WB Saunders Company. . harrisons.accessmedicine.com/server_java/Arknoid/amed/harrisons/co_chapters/ch066/ch066_p06.html www.icondata.com/health/pedbase/files/TRISOMY1.HTM