Molecular characteristics

Genetic diagnosis

This condition is caused when the gene called CNKSR2 on the X chromosome is missing or has a change within it so that it does not function properly. The CNKSR2 gene is important for normal brain development and function.

Testing for CNKSR2 gene changes is available through clinical genetic centres or neurology doctors.


The condition follows what we call an X-linked pattern of inheritance. This means that boys are affected more severely by the condition, as they have only a single X chromosome, whereas girls, if they are affected, may have milder signs as they have a second, normal X chromosome to cancel out the effect of the faulty X.

Sometimes the mother of an affected child will carry the same gene change. It’s important that each family visits their clinical geneticist to discuss the test results for their particular family as there may be implications for future pregnancies or for other family members. The geneticist would also be able to discuss the possibility of tests for future pregnancies if wished.