About Usher Syndrome

About Usher Syndrome

Usher syndrome is a genetic condition characterised by hearing loss or deafness, the progressive loss of vision and in some cases, vestibular dysfunction. The loss of vision is caused by an eye disease called Retinitis Pigmentosa (RP), which affects the light-sensitive area of tissue on the back of the eye (the retina). 

Usher Types

There are three main types of Usher syndrome – Type 1, Type 2 and Type 3. Each of these types has a number of different genes responsible for causing the syndrome. 

Type 1

  • Type 1 is comprised of 6 different subtypes; 1B, 1C, 1D, 1F, 1G and 1J depending on the specific gene mutation. 
  • Children diagnosed with Usher syndrome type 1 are profoundly deaf at birth and have a dysfunctional vestibular system.
  • Due to the vestibular dysfunction, a child with Usher syndrome type 1 will usually take longer to sit up and develop walking at a later stage than a typically developing child.
  • Gradual vision loss in the child occurs due to Retinitis Pigmentosa (RP). The severity and onset of RP varies between individuals but commonly develops before the age of 10. Vision problems are initially characterised by night blindness or tunnel vision but this also varies between individuals.

Type 2

  • Usher syndrome type 2 can be grouped into 3 subtypes, 2A, 2C and 2D.
  • In Usher syndrome type 2, the severity of hearing loss from birth can range from very mild to severe. Those with Usher syndrome type 2 do not have a dysfunctional vestibular system. 
  • Vision loss due to the RP does not usually develop until late adolescence or in some cases until the late twenties.

Type 3

  • Usher syndrome type 3 is very rare compared to the other Usher syndrome types and only one subtype has been discovered so far, with the majority of people with USH3 living in Finland.
  • A person with Usher syndrome type 3 is born with normal hearing and close to normal balance, however hearing gradually deteriorates with age. 
  • A measurable hearing loss usually occurs by puberty and vision starts to deteriorate during the teenage years and may progress during life.

Genetics of Usher Syndrome

Usher syndrome is a genetic disorder and is inherited in an ‘autosomal recessive’ manner. Basic inheritance genetics tells us that: 

  • Each person receives 23 chromosomes from each parent: 22 being non-sex (autosome) chromosomes and one sex chromosome to give a total of 46 chromosomes. 
  • These 46 chromosomes are located in every cell in the human body and contain the approximately 20,000 genes which act as blueprints for how our bodies grow, develop and function. 
  • Mutations in at least ten different genes are known to cause Usher syndrome, although in each family, only one of the Usher syndrome genes is involved.
  • Usher syndrome occurs when a child inherits two faulty copies of an Usher syndrome gene, one from each parent. This is called autosomal recessive inheritance.
  • For a couple to have a child with Usher syndrome, the mother and father must both be ‘carriers’ of a fault on the same Usher syndrome gene.  Carriers of Usher syndrome also have one functioning copy of the Usher syndrome gene, and therefore are healthy (and do not have Usher syndrome).
  • When both parents are carriers of a fault on the same Usher syndrome gene, each child has a 1 in 4 (25%) chance of having Usher syndrome, a 1 in 2 (50%) chance of being a carrier of Usher syndrome (like the parents) and a 1 in 4 (25%) chance of being neither affected by Usher syndrome nor a carrier of Usher syndrome.

Genetic Testing

A genetic test involves looking at a patient’s DNA to see if there are any mutations present.  It involves taking either a blood sample or saliva swab from the patient which is then analysed in a laboratory.  Genetic tests are important because they allow doctors to predict how severe the condition might become and what other symptoms can be expected. 

Genetic testing is available from many genetic clinics across Australia. Please see our SUPPORT section for a state by state listing. 

Skip to content