The CASK gene is “X-linked” which means that it is found in the X chromosome. Because of this, we are able to know that mutations of the CASK gene are likely to be more severe for boys than for girls. This is due to the fact that a boy only has one X chromosome (and one Y-chromosome), while a girl has two X-chromosomes. A girl with a CASK gene mutation is likely to have this in only one of her X-chromosomes, while the other X-chromosome may have a normally functioning CASK gene.

While the research is still very new, it has been theorized that the CASK gene plays an important role in both how the brain develops during infancy, as well as how it functions - specifically, how the brain cells communicate with each other (read more at eurekalert.org).

There is a wide range in the level of disability that can be caused by a mutation in a CASK gene. This can depend upon what type of mutation is found, and where along the gene it is found. Cases in which the whole gene is fully deleted or duplicated would cause more severe disability than “missense” or “nonsense” mutations that would impact just a portion of the CASK gene.