This page covers the different types of genes that cause types of Usher syndrome, and your chances of inheriting or passing on the condition.
It also covers diagnosis of Usher syndrome through hearing, sight, balance and genetic tests.
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How many types of Usher syndrome are there?
There are four types of Usher syndrome.
Types 1 and 2 are the most common. Type 3 is very rare compared to types 1 and 2.
Usher type 1
People with Usher type 1 have:
- Severe to profound hearing loss (only able to hear very loud sounds) or deafness at birth.
- Loss of night vision by age 10, with severe sight loss by midlife and more severe sight loss with age.
- Balance problems from a young age, including trouble sitting up and not walking on their own before the age of 18 months.
Usher type 2
People with Usher type 2 have:
- Moderate to severe hearing loss in early childhood.
- Loss of night vision by the time they’re teenagers, with severe sight loss by midlife.
- Normal balance.
Usher type 3
People with Usher type 3 have:
- Normal hearing at birth, with hearing loss starting in childhood.
- Loss of night vision by the time they’re teenagers, with severe vision loss by midlife.
- Around half of people also experience some problems with balance later in life.
Atypical Usher is when someone has a range of symptoms that do not fit into one of the three types above.
Genes and Usher types
Each type of Usher syndrome is caused by changes to different genes:
Usher type 1: MYO7A, USH1C, CDH23, PCDH15, USH1G, CIB2
Usher type 2: USH2A, ADGRV1, WHRN
Usher type 3: CLRN1, HARS1
Changes to MYO7A, causing type 1, and changes to USH2A, causing type 2, are the most common causes of Usher syndrome.
How is Usher syndrome diagnosed?
Usher syndrome is diagnosed through:
- Hearing tests.
- Sight tests.
- Balance tests.
- Genetic testing.
In infants, Usher type 1 and type 2 are usually picked up through newborn screening.
Newborn screening is a series of checks to see if your baby has any serious health problems from birth, including with hearing or sight.
In children of a suitable age and adults, hearing function is assessed in an audiology clinic using a test called pure tone audiometry.
An ophthalmologist (a doctor specialising in managing eye diseases) will diagnose retinitis pigmentosa from:
- Your symptoms.
- An examination of your eyes, particularly the retina.
- Different tests looking at the structure of the retina and how it’s functioning.
When examining the retina, the ophthalmologist will look for typical features of retinitis pigmentosa, such as dark spots towards the outside areas of the retina.
Other sight tests include:
- Colour vision testing.
- Visual field testing to reveal the extent of peripheral (side) vision loss. You’re asked to respond or press a button when you see flashing lights. This can be done from as young as six years of age, but results get more accurate with age.
- Optical coherence tomography. A camera detects any abnormalities in all layers of the retina, including macular oedema (a build-up of fluid in the macula in the centre of the retina).
- Autofluorescence imaging. Another camera test used to assess the health of the retina.
- Electroretinogram. A test to assess the photoreceptor cells (the cells in the retina that respond to light) to help diagnose retinitis pigmentosa. This test is not used in routine follow-up appointments or for monitoring.
A range of tests are used to find the cause of balance problems, including:
- A hearing test.
- A test to see whether your eardrums are moving normally (tympanometry).
- Stability when standing with eyes open and closed.
- Eye movements when following a target while wearing video goggles.
- Abnormal eye movements when lying down quickly on the couch.
- Abnormal eye movements when moving or shaking your head.
- Eye movements when turning on a chair.
- The balance function in each ear when stimulated with warm and cool water (caloric test).
- The reflex between the balance organs in the ears and the muscles in the neck.
Genetic testing can be used to make a diagnosis of Usher syndrome by identifying changes in specific genes that cause Usher syndrome.
It can also be used to confirm a diagnosis of Usher syndrome, made through hearing, sight and balance tests.
For a genetic test, you usually need to give a blood sample.
DNA – the substance that contains your genes – is then taken from the blood sample and tested for changes in specific genes that cause Usher syndrome.
If there’s a history of Usher syndrome in your family, early genetic testing can detect the condition in your child before any symptoms develop.
This is extremely important for putting young children on the right path to managing and living with Usher syndrome as early as possible in life.
To arrange a genetic test, ask your GP for a referral to a genetic clinic.
When you ask for a genetic test, your GP might suggest you have genetic counselling. If they don’t, ask them to refer you for genetic counselling.
In genetic counselling, a specially trained professional will give you and your family information on your family member’s specific genetic condition.
This should help you to make decisions and understand the impact genetic testing might have on you, your family, employment and insurance before going ahead with a genetic test.
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This content was last reviewed in April 2022. We’ll review it again next year.