We think that the syndrome is caused by just one faulty gene. Every cell in our bodies contains about 50,000 genes. We each have two copies of each of these genes, one we inherit from our mother and the other from our father. In many cases we only need one good copy of the gene and one faulty copy is then not a problem. However, this is not always the case and for other genes we need both copies of the gene to be working correctly. In de Lange Syndrome we think that one copy of a very important gene has a fault in it and that the fault occurs I either the egg or the sperm.
The chances of having another child with the syndrome are very small. There are only a few known cases in the world of a couple having two children with the syndrome. We are therefore more than 99% sure it will not happen again in your family. We think that in these cases a fault occurred early on in the development of the ovary or the testis and that instead of just one copy of an egg or sperm carrying the faulty gene there were in fact several eggs or sperm with the fault. Even though couples know that it is extremely unlikely that they will have another child with the syndrome they feel very unlucky, especially if it is their first child, and often believe that things will go wrong again if they have another child.