<unk>  is the result of trisomy 13, meaning each cell in the body has three copies of chromosome 13 instead of the usual two. A small percentage of cases occur when only some of the body's cells have an extra copy; such cases are called mosaic trisomy 13.<unk>  can also occur when part of chromosome 13 becomes attached to another chromosome (translocated) before or at conception in a Robertsonian translocation. Affected people have two copies of chromosome 13, plus extra material from chromosome 13 attached to another chromosome. With a translocation, the person has a partial trisomy for chromosome 13 and often the physical signs of the syndrome differ from the typical<unk> . Most cases of<unk>  are not inherited, but occur as random events during the formation of reproductive cells (eggs and sperm). An error in cell division called non-disjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of the chromosome. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra chromosome 13 in each of the body's cells. Mosaic<unk>  is also not inherited. It occurs as a random error during cell division early in fetal development.<unk>  due to a translocation can be inherited. An unaffected person can carry a rearrangement of genetic material between chromosome 13 and another chromosome. This rearrangement is called a balanced translocation because there is no extra material from chromosome 13. Although they do not have signs of<unk> , people who carry this type of balanced translocation are at an increased risk of having children with the condition. Recurrence risk Unless one of the parents is a carrier of a translocation, the chances of a couple having another trisomy 13 affected child is less than 1%, below that of Down syndrome.
Patau syndrome
Bart syndrome
McGillivray syndrome
Sotos syndrome
Keutel syndrome
Cortes Lacassie syndrome
Bart–Pumphrey syndrome
Fryns-Aftimos syndrome