Patau syndrome


A syndrome caused by a chromosomal abnormality, in which some or all of the cells of the body contain extra genetic material.

This extra genetic material disrupts normal development, causing multiple and complex organ defects.

It is a Trisomy 13.

Each cell contains a full extra copy of chromosome, a disorder known as trisomy 13 or trisomy D, or because each cell contains an extra partial copy of the chromosome,

Full trisomy 13 is caused by nondisjunction of chromosomes during meiosis.

The mosaic form is caused by nondisjunction during mitosis.

The risk of this syndrome in the offspring increases with maternal age at pregnancy, with about 31 years being the average.

Patau syndrome affects somewhere between 1 in 10,000 and 1 in 21,700 live births.

Most affected people die in infancy, some survive for months or years.

Facial features included sloping forehead with a nose superior to a single central palpebral fissure.

Of fetuses that survive to gestation and subsequent birth, common abnormalities may include:

Intellectual disability and motor disorder


Failure of the forebrain to divide properly

Structural eye defects


Musculoskeletal and cutaneous changes




Congenital trigger digits

Low-set ears

Prominent heel

Rocker-bottom feet


Abnormal palm pattern

Overlapping of fingers over thumb

Cutis aplasia

Cleft palate


Abnormal genitalia

Kidney defects

Heart defects-ventricular septal defect, Patent Ductus Arteriosus


Single umbilical artery

It is the result of trisomy 13, meaning each cell in the body has three copies of chromosome 13.

In a small percentage of cases occur when only some of the body’s cells have an extra copy, called mosaic Patau.

The syndrome can also occur when part of chromosome 13 becomes attached to another chromosome before or at conception in a Robertsonian translocation.

Affected people have two copies of chromosome 13, plus extra material from chromosome 13 attached to another chromosome.

With a translocation, the person has a partial trisomy for chromosome 13 and often the physical signs of the syndrome differ from the typical Patau syndrome.

Most cases occur as random events during the formation of reproductive cells, with an error in cell division called non-disjunction which can result in reproductive cells with an abnormal number of chromosomes.

Mosaic Patau syndrome is also not inherited. It occurs as a random error during cell division early in fetal development.

Patau syndrome due to a translocation can be inherited.

Unless one of the parents is a carrier of a translocation, the chances of a couple having another trisomy 13 affected child is less than 1%.

Physical development occurs more slowly than in normal children

Diagnosis is usually based on clinical findings.

Fetal chromosome testing will show trisomy 13.

Unlike Edwards syndrome and Down syndrome, the quad screen does not provide a reliable means of screening for this disorder.

Many infants die in the first few days or weeks due to severe neurological problems or complex heart defects.

More than 80% of children with Patau syndrome die within the first year of life.

Children with the mosaic variation are usually affected to a lesser extent.

In a Canadian study of 174 children with trisomy 13, median survival time was 12.5 days, with 1 and 10 year survivals at 19.8% and 12.9% respectively.

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