Cri-du-Chat Syndrome was first described in `963 by Professor J. as a hereditary congenital syndrome caused by a deletions in the short arm of chromosome 5. For this reason, Cri-du-Chat syndrome is also called 5p minus syndrome. Interestingly, Professor Lejeune is also credited with discovering the association of Downs Syndrome with a trisomy on the 21st chromosome.
Cri-du-Chat is a relatively rare genetic condition with an estimated incidence of between 1 out of every 25,000 births and 1 out of every 50,000 births. There are more children being diagnosed now that genetic testing is more accurate. Approximately 80% are caused by a de novo deletion in the child, 10-13% by a balanced translocation in either parent, and 7-10% result from rare genetic anomalies. It is thought that more girls than boys are born with Cri-du-Chat, with three girl births to two boy births. It is possible to detect Cri-du-Chat Syndrome with amniocentesis or CVS in the first trimester of pregnancy, but at this point it is not possible to tell how severely affected the baby will be. Cri-du-Chat is an extremely variable syndrome, ranging from very mild to very severe, so researchers believe that understanding how the syndrome will affect the baby before it is born is the next crucial step.
There are a variety of genetic arrangements that code for Cri-du-Chat. The most common is an unbalanced translocation, which occurs when a piece of one chromosome breaks off and attaches to another, different chromosome. If either parent has a balanced translocation, the child may be born with an unbalanced translocation. This happens in about 10% of children with Cri-du-Chat Syndrome, although in a few cases the unbalanced translocation is de novo. This is one reason that parents of Cri-du-Chat children or individuals with Cri-du-Chat in their immediate families should see a genetics counselor before contemplating pregnancy.
