Koolen-De Vries syndrome whose scientific name is Microdeletion 17q21.31 is a rare genetic disorder .
Genetic disease means disease caused by the anomaly on the behavior of a gene.
Rare means that the number of people affected is limited compared to the general population.
Microdeletion 17q21.31 is therefore a genetic condition in which a tiny fragment is missing from one of the 46 chromosomes, there is a lack of a small amount of genetic material.
A small number of people with Koolen-De Vries syndrome do not have a microdeletion of chromosome 17 but a mutation in the KANSL1* gene that results in a non-functioning copy of the gene.
There are no exact data on the number of people affected in France or in the world.
The incidence of people affected by the deletion is 1/55,000 births.
However, it is impossible to quantify the number of births in the case of the mutation.
* Translation of the definition of the KANSL 1 gene from the site https://ghr.nlm.nih.gov/gene/KANSL1 : The KANSL1 gene provides instructions for the creation of a member (subunit) of a group of interacting proteins called the KAT8 regulatory NSL complex. This complex is classified as a histone acetyltransferase (HAT) complex. It helps regulate gene activity (expression) by altering chromatin, the complex of DNA and proteins that packages DNA in chromosomes. The protein produced from the KANSL1 gene is found in most organs and tissues of the body before birth and throughout life. Through its involvement in controlling the activity of other genes, this protein plays an important role in the development and functioning of many parts of the body.