Patau's syndrome
Overview
Patau's syndrome is a serious, rare genetic disorder caused by having an additional copy of chromosome 13 in some or all of the body's cells. It's also called trisomy 13.
Symptoms
Babies with Patau's syndrome can have a wide range of health problems. Their growth in the womb is often restricted, resulting in a low birth weight, and 8 out of 10 will be born with severe heart defects. The brain often does not divide into 2 halves. This is known as holoprosencephaly. When this happens, it can affect facial features and cause defects such as: cleft lip and palatean abnormally small eye or eyes (microphthalmia)absence of 1 or both eyes (anophthalmia) Other abnormalities of the face and head include: smaller than normal head size (microcephaly)ear malformations anddeafness Patau's syndrome can also cause other problems, such as: an abdominal wall defect where the abdomen does not develop fully in the womb, resulting in the intestines being outside the body, covered only by a membrane – this is known as an exomphalos or omphalocoeleabnormal cysts in the kidneys There may also be abnormalities of the hands and feet, such as extra fingers or toes (polydactyly) and a rounded bottom to the feet, known as rocker-bottom feet.
Causes
Patau's syndrome happens by chance and is not caused by anything the parents have done. Most cases do not run in families (they're not inherited). They happen randomly during conception, when the sperm and egg combine and the foetus starts to develop. There's an error when the cells divide, resulting in an additional copy, or part of a copy, of chromosome 13, which severely affects the baby's development in the womb. In many cases, the baby dies before reaching full term(miscarriage)or is dead at birth(stillbirth). In most cases of Patau's syndrome, a baby has a whole extra copy of chromosome number 13 in their body's cells. This is sometimes known as trisomy 13 or simple trisomy 13. In some cases of Patau's syndrome, genetic material is rearranged between chromosome 13 and another chromosome. This is called a chromosomal translocation. Patau's syndrome that arises because of this can be inherited. Sometimes only some cells have the extra copy of chromosome 13. This is known as trisomy 13 mosaicism. Occasionally, only part of 1 chromosome 13 is extra (partial trisomy 13). The symptoms and features of both mosaicism and partial trisomy tend to be less severe than in simple trisomy 13, resulting in more babies living longer. Genetic Alliance UK has more information about chromosome disorders