Patau syndrome

Patau syndrome

Description, Causes and Risk Factors:

Patau's syndrome carries a high mortality rate with multiple congenital abnormalities which result in severe physical and mental impairment.

It is usually in 80% of cases due to a freestanding trisomy with an extra number 13 chromosome, instead of the usual pair in all cells. An unbalanced chromosome translocation can also occur, commonly a Robertsonian translocation. This is when an extra copy of chromosome 13 is attached to another chromosome. Rarely, structural chromosome abnormalities can occur where only part of chromosome 13 is duplicated. There may also be mosaic variations in which some cells are normal with 46 chromosomes and others have the extra chromosome. Infants with mosaic variations tend to be less severely affected.

Patau's syndrome is the least common and the most severe of the viable trisomies. In liveborn infants, it is more likely that the affected infant is female rather than male. This is thought to be due to the fact that male fetuses with trisomy 13 are more likely to be lost due to miscarriage or stillbirth. This ratio continues as the infant ages, with females more likely to survive.

The incidence in live births is 1 in 21,700 and may be falling due to antenatal screening and selective termination of pregnancy.

Signs & Symptoms:

• Intrauterine growth retardation and low birth weight.

• Congenital heart defects.

• Holoprosencephaly (presence of a single forebrain hemisphere or lobe; cycloplia occurs in the severest form. It is often accompanied by a deficit in median facial development).

• Cleft lip and palate.

• Microphthalmia or anophthalmia.

• Nasal malformation.

• Hypotelorism (reduced distance between the eyes) or cyclops.

• Other brain and central nervous system abnormalities including:

• Neural tube defects.

• Other anatomical defects of the brain.

• Severe learning disability.

• Problems with control of breathing (central apnoea).

• Other craniofacial abnormalities.

• Microcephaly.

• Ear malformations and deafness.

• Capillary haemangiomata.

• Gastrointestinal abnormalities: omphalocele, exomphalos, hernias.

• Urogenital malformations.


Cytogenetic studies and chromosomal analysis will confirm the diagnosis.

Organ systems will need specific investigation depending on the abnormality, e.g. echocardiography for cardiac abnormalities, skeletal radiography, etc.


Treatment of a liveborn infant is generally supportive but life sustaining measures are not always carried out. Considerable thought and discussion is recommended before undertaking measures such as surgical correction of abnormalities. Nasogastric or gastrostomy feeding is feasible but it is questionable if this is prolonging life or prolonging death. Parents will need a great deal of support and counselling. Support organisations may be useful.

If Patau's syndrome is due to an unbalanced chromosome translocation or structural chromosome abnormality, both parents should undergo chromosomal analysis. It may be that the translocation in the infant occurred de novo (from the beginning) but a balanced translocation may be found in one of the parents. This has significance for future pregnancies because of a higher risk of recurrence. Other family members may also be affected. Screening and/or prenatal diagnosis should be offered for future pregnancies. For full trisomy 13, the risk of recurrence is approximately 0.5% above the mother's age-related risk. Risk may be higher if a parent carries a balanced translocation. Referral should be made to a geneticist as appropriate.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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