Trisomy 13 (Patau Syndrome)

An additional chromosome 13 causes trisomy 13, also known as the Patau syndrome after the person that first described it. It affects one in 10,000 people. Trisomy 13 involves severe developmental disorders; babies are born exceedingly underweight and abnormalities include malformations of the inner organs, in particular the brain, heart, kidneys and digestive tract.Cardiac defects are present in about 80 per cent of cases, mostly in the form of ventricular septal defects. The heart may be positioned in the right side of the thorax and can be mirror inverted.Most affected children die within the first two months of life, very few reach one year.