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
- 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
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
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.
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