Patau syndrome, also called trisomy 13, is a genetic disorder caused by the presence of an extra chromosome 13. It is the least common and the most severe of the viable trisomies.

FREQUENCY OFOCCURRENCESeen 1 in 10,000 births
• In utero death occurs in over 95% of fetuses with this chromosomal anomaly.
INHERITANCESporadic / not inherited
• Most cases of Patau syndrome are sporadic, and not inherited, including mosaicism.
• Patau syndrome caused by a translocation can be inherited. A carrier can have a rearrangement of genetic material between chr 13 and another chromosome. This is called a balanced translocation, because there is no extra material from chr 13. Although they do not have signs of Patau syndrome, people who carry this type of balanced translocation are at an increased risk of having children with the condition..
LIFE EXPECTANCYLimited lifespan, with 2.5 days of median survival
• 90% of infants die before 1 year of age. Prolonged survival is more common in cases ofmosaic or partial trisomy and in the absence of severe brain malformations.
CAUSEA third chromosome 13 appearing in all or some of the cells
• Primary trisomy: the presence of a third chr 13 in all cells (75% of all cases).
• Unbalanced translocation: an extra portion of chr 13 attached to another chromosome,which may be due to a balanced translocation of one parent.
• Mosaicism: some normal cells with 46 chromosomes, others with extra chr 13.


People with Patau syndrome have multiple congenital abnormalities, which result in severe physical and mental impairment. The syndrome carries a high mortality rate. It causes such serious birth defects that only few babies survive to their first birthday. Profound mental retardation and developmental delay occur in survivors. Seizures and feeding difficulties are also common.

Key features:

  • Intrauterine growth retardation
  • Low birth weight
  • Low muscle tone (hypotonia)
  • Small head (microcephaly)
  • Brain malformations (holoprosencephaly)
  • Craniofacial abnormalities
  • Ocular anomalies
  • Extra fingers or toes (polydactyly)
  • Clenched hands
  • Hyporeactivity
  • Congenital heart defects
  • Problems with control of breathing (central apnoea)
  • Gastrointestinal abnormalities
  • Urogenital malformations
  • Severe psychomotoric retardation

Management of children with trisomy 13 is planned on a case-by-case basis and depends on the individual circumstances of the patient. The treatment of the syndrome focuses on the particular physical problems with which each child is born.

Surgery may be necessary to repair heart defects or body abnormalities. Many infants do not survive the first few days or weeks due to severe neurological problems or complex heart defects.