Usher syndrome is inherited, which means that it is passed from parents to their children through changed or mutated genes. Usher is autosomal recessive. 

Autosomal means that both males and females can have the disorder and can pass along the disorder to a child.

Recessive means that a person must inherit a change in the same gene from each parent in order to have the disorder. 

'Carrying' the gene

A person with one changed gene does not have the disorder, but can pass either the changed or the unchanged gene on to his or her child. They are said to be a carrier because they ‘carry’ the gene with a mutation, but show no symptoms of the disorder.

Usually, parents who have normal hearing and vision do not know if they are carriers of an Usher syndrome gene mutation. Currently, it is not possible to determine whether an individual who does not have a family history of Usher syndrome is a carrier. This may change as scientists learn more about the genes responsible for Usher syndrome.

Every individual has two copies of the same gene. When two carriers of the same Usher syndrome gene have a child together, with each birth there is a:

• One in four chance of having a child with Usher syndrome
• Two in four chance of having a child who is a carrier
• One in four chance of having a child who neither has Usher syndrome nor is a carrier
• Spontaneous mutations in genes can occur, but are very rare. 

Identified genes

So far nine genes have been identified that cause the disorder. They are:

• Type one Usher syndrome: MY07A, USH1C, CDH23, PCHD15, SANS
• Type two Usher syndrome: USH2A, VLGR1, WHRN
• Type three Usher syndrome: USH3A

Genetic testing

Genetic testing and diagnosis is available at a limited number of laboratories around the world (for more information follow this link to the National Center for Biotechnology Information). 

However, research and technology around genetic testing are rapidly developing and becoming more widely available. Recently Professor Graeme Black, Professor of Genetics and Ophthalmology at Central Manchester University Hospital and Director of the Biomedical Research Centre in Manchester, UK, announced a new test that can analyse more than 100 genes and will allow experts to diagnose a range of conditions, including Usher syndrome. 

Genetic screening is not available at this time.