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Patau syndrome

Also known as: Trisomy 13, 13+ syndrome

Background

Patau syndrome is a chromosome abnormality where the child has an extra chromosome 13 in every cell. It is a rare condition, seen in about 1 in 7,000 live births. There are three types of the syndrome:

  • full form - in this form, every cell in the body has three chromosome 13s instead of two.
  • mosaic form - in this form, some cells have two chromosome 13s while others have three. The extent and severity of the condition will depend upon the ratio of normal to abnormal cells.
  • partial form - in some cases there may be an extra copy of part of chromosome 13. This is referred to as 'partial trisomy 13'. This may be due to a ring chromosome or an unbalanced translocation. The effects of this may be milder and would require further specialist advice.

Babies with the full form may not survive to term and around half die in the first 6 months of life. A few children will survive past a year and there are small numbers of individuals who survive into adulthood.

Credits

Medical text written December 2011 by Dr Nora Shannon. Last updated November 2016 by Dr Nora Shannon, Consultant Clinical Geneticist, Nottingham University Hospital, Nottingham, UK.

Although great care has been taken in the compilation and preparation of all entries to ensure accuracy, we cannot accept responsibility for any errors or omissions. Any medical information is provided is for education/information purposes and is not designed to replace medical advice by a qualified medical professional.

What are the symptoms?

Characteristic features include:

  • low birth weight
  • heart defects
  • structural eye defects
  • cleft lip and/or palate
  • meningomyelocele (a spinal defect; see entry Spina Bifida)
  • omphalocele (abdominal defect; see entry Abdominal Exstrophies)
  • abnormal genitalia
  • low-set ears
  • abnormal palm creases
  • scalp defects
  • extra digits and overlapping of fingers over thumb
  • abnormal brain development (holoprosencephaly)
  • learning disability

How is it diagnosed?

Patau syndrome is often detected during pregnancy (see prenatal diagnosis) and some parents will opt not to continue the pregnancy. In some cases a spontaneous miscarriage will occur.

Sometimes a baby may be born with features of Patau syndrome after normal scans in the pregnancy. In this situation, a blood sample from the baby will be sent for karyotype analysis to confirm the diagnosis.

How is it treated?

Parents should meet with the obstetric and neonatal teams to discuss the diagnosis and to prepare for delivery and the care of their baby. It is likely that the baby will be admitted to the special care baby unit, and will require supportive treatments over the first days of life. Many babies with Patau syndrome have congenital problems such as a cleft lip/palate or heart defects. They will need treatments to alleviate symptoms and improve their quality of life.

Sadly, many children with Patau syndrome will be lost during a pregnancy, are stillborn or do not survive past the first week of life. A few children will live longer than one year and there are some cases of adults with this condition. If a baby is well enough to leave hospital, community support arrangements should be put in place, and follow-up plans made with the local paediatric team.

Inheritance patterns and prenatal diagnosis

Inheritance patterns
Patau syndrome usually happens as 'one off' (sporadic) event in a family. In this situation the chance of another baby with Patau syndrome in the family is low. In rare cases, a balanced translocation in a parent can give rise to an unbalanced translocation in their child. This situation is detected on the baby's karotype.

Prenatal diagnosis
Screening for Patau syndrome is now offered at 10-14 weeks of pregnancy using a combined blood test and ultrasound scan as part of antenatal care. If this screening test gives a high risk result a further definitive test (chorionic villous sample test or amniocentesis) is offered.

Features of Patau syndrome can be detected on the routine detailed anomaly scan at 20 to 22 weeks gestation (see prenatal diagnosis section) in around 80% of cases. In this situation a definitive chromosome test will be offered. Parents may opt not to continue with the pregnancy. In many cases the baby is lost as a spontaneous miscarriage.

Is there support?

Information and support in the UK for Patau syndrome is provided by SOFT UK (see entry Edward's syndrome).

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