A chromosomal abnormality in which there are three copies of chromosome 13 instead of the usual two. It is a congenital (present from birth) condition and causes low birth weight and a number of other deformities including hare lip or cleft palate; low set ears; eye deformities; micrognathia (under sized jaw); extra digits; and malformation of the genitalia. There can also be extreme deformities of the internal organs, such as heart defects, meningomyelocele and exomphalos (in which part or all of the intestines protrude through the naval). Many children with Patau’s syndrome do not survive past the age of 2, and those that do survive have learning difficulties. Occasionally affected children can have a mixture of normal and abnormal cells, and they may have milder forms of the condition.
The condition can be diagnosed at an early stage of pregnancy by a test such as amniocentesis or chorionic villus sampling. In addition, genetic counselling can also be offered.