Autosomal means that the disorder is not gender-specific. Boys and girls have the same chance of having Usher Syndrome.
Recessive means that the mutations are inherited from both parents. The father has one mutation and one healthy copy in one Usher gene. The mother also has one mutation and one healthy copy in the same Usher gene. Both are carriers and do not show any symptoms of Usher Syndrome. The ‘healthy copy’ is dominant. A child of this parents has:
- 25% chance of getting two ‘healthy copies’ from both parents.
- 50% chance of getting one healthy copy and one mutation from its parents. This child will also be carrier, but does not show any symptoms of Usher Syndrome.
- 25% chance of receiving both mutations from both parents. Then the disorder will show.
Usher Syndrome often comes unexpectedly, because most parents do not know that they are carrier. Usher Syndrome is very rare; only one out of 75 people carries a mutation in one of the 10 Usher genes. Examples:
- The parents are both carriers of one mutation in the Usher 1B gene and pass this on to their child. In this case the child has 25% chance to Usher Syndrome type 1B.
- The father is carrier of a mutation in the USH 1B gene en the mother is carrier of a mutation in the USH 2A gene. These mutations can be passed on to their child, but the child will not have Usher Syndrome. The child is carrier of mutations in two different Usher genes though.