Edwards syndrome is a chromosome abnormality where the child has
an extra chromosome 18 in every cell. It is a rare disorder, seen
in about 1 in 4,400 live births.
There are three types of the syndrome:
- Full form - in this form, every cell in the body has three
chromosome 18s instead of two (94 per cent of cases).
- Mosaic form - in this form, some cells have two chromosome 18s
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 18. This is referred to as 'partial trisomy 18'. The
effects of this may be milder and would require further specialist
Children with the full form do not often survive beyond infancy,
with about 10 in 100 (10%) expected to live past one year of age.
Those affected by the mosaic and partial forms may sometimes
survive into adulthood.
Medical text written October 2010 by Dr Kate Baker, Specialty
Registrar in Clinical Genetics, Addenbrookes Hospital, Cambridge,
UK and Dr Nora Shannon. Last updated November 2016 by Dr Nora
Shannon, Consultant Clinical Geneticist, Nottingham University
Hospital, Nottingham, UK.
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