What is Usher Syndrome?

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Usher syndrome (USH) is a rare, genetically inherited disease and its main symptoms are, sensorineural hearing loss and retinitis pigmentosa (RP) which causes a slow progressive loss of sight. For some USH types, there are also vestibular (balance) issues too. 

Usher syndrome is the leading genetic cause for combined hearing and sight loss. It is estimated that over 400,000 people worldwide have Usher syndrome. Since the data on the number of USH patients in Ireland is limited, it's our estimate there could be around 200-260 people living with this condition here.  

Inside the eye, there is a thin layer of tissue that lines the back of the eye called the retina. This layer is made up of millions of light-sensitive photoreceptor cells called rods and cones. The function of these cells is to take in the visual information and process it to the brain via the optical nerve helping us to see. Rods are essential for night-vision helping us to see in the dark and dull lighting, while cones are needed for day vision, colour and sharp vision. Retinitis pigmentosa (RP) associated with USH affects these photoreceptors cells causing these cells to degenerate slowly over time. The rods are usually the first to be affected and this explains why night-blindness is often the first sign of RP. Over time, which can be over many years/decades, there is a slow loss of the peripheral vision leading to tunnel vision. Central vision often remains intact until end-stage RP, as this area of the retina is heavily populated with cones. 

Many people with Usher syndrome retain some useable vision into older age, however some do experience a full loss of sight. Unfortunately, there is no way to predict the onset of symptoms, how it will progress, and how severe it may be. 

In the inner ear, the cochlea contains thousands of tiny hair cells. It is the role of these hair cells to respond to the different sounds coming into the ear by sending electrical impulses to the brain via the auditory nerve to help us hear. In Usher syndrome, these tiny hair cells are typically damaged thus impacting hearing. This is known as sensorineural hearing loss. The more severely damaged these hair cells are the greater the hearing loss. Some are born with little to no hearing, as typically seen in those with USH type 1. Others may have some but not all of these hair cells completely damaged, and with the help of hearing aids, which amplifies sounds, many can access sound and speech. Some of those with USH type 2, and those with USH type 3 and USH type 4, experience a progressive loss of hearing over time. 

For those who are born with a severe to profound loss, or for those who experience a progressive hearing loss, cochlear implants can be an option to give good access to sound and speech. These are electronic devices that replaces the function of the damaged tiny hair cells by sending electrical impulses to the brain. 

In the inner ear, there are three loops known as the semi-circular canals, and each of these canals have a different role to play in determining balance, motion and location. Just like in the cochlea, each of these canals contains hair cells and fluids. It is due to these hair cells being damaged that can cause balance issues associated with Usher syndrome. This is especially noted in those with USH type 1 where babies/toddlers tend to be slower to sit up and/or are later to walk than their peers. 

However, these hurdles can be overcome in time as the brain learns to adapt along with rehab exercises provided by occupational therapists and physiotherapists.

Usher syndrome is catergorised into four major types, 1,2,3, and 4. The chart above shows the typical onset of hearing, sight, and balance loss experienced by those with a certain type of Usher syndrome. However, this is not representative of all those with Usher syndrome as the symptoms can vary in onset and severity. 

There are also cases of non-syndromic Usher syndrome, where a person has been genetically tested and has an identified USH gene, but has only one of the symptoms associated with this condition.

Usher Syndrome Types and Subtypes

Usher Syndrome Type 1 (USH1)

USH1B USH1C USH1D USH1f USH1G USH1J 

Usher Syndrome Type 2 (USH2)

USH2A USH2C USH2D 

Usher Syndrome Type 3 (USH3)

USH3A USH3B  

Usher Syndrome Type 4 (USH4)

USH4 

Usher syndrome may be clinically diagnosed by carrying out a range of tests for hearing, vision, and balance. To confirm a clinical USH diagnosis, genetic testing must be performed to find the causative USH gene. 

Tests may include: 

• A hearing test:  An audiologist performs a hearing test to measure the frequency and loudness of sounds that a person can hear. 

• An electroretinogram: An electroretinogram (ERG) is a test that measures the electrical responses of the light-sensitive (photoreceptor) cells in the retina in response to light stimuli. 

• Retinal exam: A retinal exam is performed by an ophthalmologist who exams the back of an (dilated) eye to look for any changes that is commonly associated with retinitis pigmentosa. 

• A visual field test: A visual field (VF) test measures a person’s peripheral vision. 

• Genetic test. A genetic test involves taking a small blood sample and having it analysed in a lab to find a mutation in the gene that is known to cause Usher syndrome.

In some cases, a person may be clinically diagnosed with Usher syndrome due to their symptoms, but genetic testing may not yet be able to confirm this diagnosis as the causative USH gene may not yet have been identified. 

With a good support network and the right accommodations provided when necessary, people with Usher syndrome lead independent and fulfilling lives with careers and families of their own. We regularly share stories from many individuals highlighting this and our USH community on our social media platforms. The USH community is a diverse and large community where many individuals and families have made connections worldwide providing encouragement and support to each other. We strongly encourage anyone feeling alone or looking for support to reach out to us. We can help you to make connections, and provide support where possible.