What is the chance of passing Rett syndrome on to a child?

The chance of passing on Rett syndrome to a child depends on the genetic type of the condition and the sex of the child.

- For the most common type of Rett syndrome, caused by mutations in the MECP2 gene, the condition is usually passed on in an X-linked dominant pattern, meaning the mother carries one mutated copy of the gene on the X chromosome and can pass it on to either son or daughter.

- Sons who inherit the mutated gene will usually have more severe symptoms of Rett syndrome than daughters, who may have milder symptoms or be unaffected carriers of the mutation.

- Daughters who inherit the mutated gene have a 50% chance of developing Rett syndrome, while sons who inherit the mutated gene have a 50% chance of being affected and a 50% chance of being unaffected carriers.

- Two less common types of Rett syndrome, caused by mutations in the CDKL5 or FOXG1 genes, are inherited in an autosomal dominant pattern, meaning only one copy of the mutated gene needs to be present to cause the condition. In these cases, the risk of passing on the condition to a child is generally 50% for both male and female children.