The Usher Syndrome Coalition has many webpages and published articles on Usher Syndrome. For questions that have already been answered elsewhere, we will just repeat the questions on this page but redirect you to our other pages for the answers. For new questions or additional answers, we will provide the answers on this page itself. Also we will provide India-specific information, wherever applicable.
Usher Syndrome Coalition Frequent Questions page
USH India-published FAQ article in Earguru.in
What is Usher Syndrome?
Usher syndrome is a rare genetic disease that causes both hearing and vision loss. It is the most common cause of combined hearing and vision loss, also known as deafblindness. The hearing loss associated with Usher syndrome typically starts at birth or soon thereafter, but it may go undetected for years. The severity of hearing loss varies depending on the type of Usher syndrome, with some children being born with moderate to profound hearing loss. The vision loss associated with Usher syndrome is due to retinitis pigmentosa (RP), which results in the deterioration of peripheral vision as well as night blindness. In some types of Usher syndrome, there is also balance problems due to abnormal development of the vestibular hair cells.
Additional resources:
What causes Usher Syndrome?
Usher syndrome is an inherited condition. The condition is caused by mutations in specific genes that are passed down from parents to their children. Researchers have discovered mutations in 11 genes that have resulted in the different subtypes of Usher syndrome. When a gene is mutated, it causes certain cells in our body to act differently, leading to the symptoms of Usher syndrome.
What are the Types of Usher Syndrome?
Researches have identified 3 major Usher types, designated as type 1, type 2 and type 3, which are further subdivided into subtypes (based on the mutated gene). Ongoing research indicates that there is a possible Usher type 4.
Usher syndrome type 1 accounts for 35-40% of all Usher cases, type 2 accounts for 60-65%, while type 3 accounts for 0-5%.
Technical details are available in "Usher Syndrome", National Library of Medicine, February 2022.
What is Usher Syndrome Type 1 (USH1)?
Usher syndrome type 1 (USH1) is further subdivided into these subtypes: USH1B, USH1C, USH1D, USH1F, USH1G. There is no USH1A.
Hearing loss: profound hearing loss at birth.
Vision loss: Retinitis Pigmentosa starts before age 10.
Vestibular/Balance issues: severe.
A more technical answer can be found here:
Usher Syndrome Type I. 2020. Robert Koenekoop, et al. GeneReviews.
What is Usher Syndrome Type 2 (USH2)?
Usher syndrome type 2 (USH2) is further subdivided into these subtypes: USH2A, USH2C, USH2D. There is no USH2B.
Hearing loss: moderate to severe hearing loss at birth.
Vision loss: Retinitis Pigmentosa starts in late childhood or early teens.
Vestibular/Balance issues: none
A more technical answer can be found here:
Usher Syndrome Type II. 2023. Robert Koenekoop, et al. GeneReviews.
What is Usher Syndrome Type 3 (USH3)?
Usher syndrome type 3 (USH3) is further subdivided into these subtypes: USH3A, USH3B
Hearing loss: normal hearing at birth. Progressive loss in childhood or early teens.
Vision loss: Progressive vision loss. Varies in severity. Night vision problems begin in teen years.
Vestibular/Balance issues: progressive balance loss in some. Possible late onset.
What is Atypical and Ultra-Rare Usher Syndrome?
A fourth Usher type called atypical Usher syndrome has been identified to include cases where the symptoms do not conform with the typical symptoms of USH1, USH2 and USH3. Cases included individuals who tested positive for USH genes and have retinitis pigmentosa, but they have no hearing loss, and vice-versa (with hearing loss but no vision loss). For more details, refer to Atypical and Ultra-rare Usher Syndrome: A Review and Usher Syndrome Type 4.
What is deafblindness?
Deafblindness is a condition characterized by combined hearing loss and vision loss. Deafblindness can range from mild hearing and vision loss, to profound hearing and vision loss.
What are the causes of deafblindness?
There are more than 70 possible causes of deafblindness identified in the 2019 National Deaf-Blind Child Count Report (USA). Some of these causes may have similar symptoms as Usher syndrome (i.e. hearing loss and retinal impairment) that they may be misdiagnosed as Usher syndrome when genetic testing is not done (source).
Deafblindness may be present at birth (congenital deafblindness), or it might develop later in life (acquired deafblindness).
Genetic conditions that can cause deafblindness:
(Not a comprehensive list)
- Usher syndrome
- CHARGE syndrome
- Alstrom syndrome
- ABHD12 gene mutations
- PRPS1 gene mutations
- CEP78 gene mutations associated with cone-rod dystrophy and deafness
- Leber's congenital amaurosis
- Heimler syndrome
- Down syndrome
- Stickler syndrome
- Zellweger Spectrum Disorder
- Cornelia de Lange syndrome
- Dandy-Walker syndrome -- may or may not be genetic
Some causes of congenital non-genetic deafblindness:
(Not a comprehensive list)
- Complications from premature birth
- Infections during pregnancy
- Rubella (German Measles)
- Toxoplasmosis
- Congenital Cytomegalovirus (CMV)
- Dandy-Walker syndrome
- Hydrocephalus
- Foetal alcohol syndrome
- Celebral Palsy
- Microcephaly
Some Causes of acquired deafblindness:
(Not a comprehensive list)
- blindness + age-related hearing loss
- deafness + age-related vision loss such as age-related macular degeneration (AMD), cataracts and glaucoma
- accidents
Sources:
- National Center of Deaf-Blindness: Causes of Deaf-Blindness
- Hiding in plain sight: genetic deaf-blindness is not always Usher syndrome
- Sense International
What is the Prevalence Rates of Usher Syndrome and Deafblindness?
Here we note the estimates of prevalence rates of Usher syndrome and deafblindness, taken from various trusted sources (listed below). We then use these prevalence estimates, along with estimates of the population size at a given date, to estimate the number of people possibly affected by Usher syndrome and deafblindness in India and the world.
Disclaimer: The percentages and numbers provided here are simply estimates based on the prevalence rates reported in various research papers. They are provided to guide various organization working with the deafblind and Usher syndrome communities.
Global estimates as of 5 November 2022:
Estimated number of people with Usher syndrome worldwide = 3,20,000 to 13,60,000 (3.2 lakhs to 13.6 lakhs).
Details:
Sources:
- Global population = 8 billion (source [1])
- Percentage with severe deafblindness = 0.2% (source [2]) or approximately 1,60,00,000 people
- Percentage with mild deafblindness = 2% (source [2]) or approximately 16,00,00,000 people
- Percentage with Usher syndrome = 4 to 17 people per 1,00,000 people (source [3]) or approximately 3,20,000 to 13,60,000 people
India estimates as of 5 November 2022:
Estimated number of people with Usher syndrome in India = 56,000 to 2,80,000 (0.5 lakhs to 2.8 lakhs)
Details:
- India population = 1.4 billion (source [1])
- Percentage with hearing impairment only = 0.42% (source [4]) or approximately 59,00,000 people
- Percentage with vision impairment only = 0.42% (source [4]) or approximately 59,00,000 people
- Percentage with severe deafblindness = 0.2% (source [2]) or approximately 28,00,000 people
- Percentage with mild deafblindness = 2% (source [2]) or approximately 2,82,00,000 people
- Percentage with Usher syndrome, lower limit = 4 per 1,00,000 people (source [3]), or approximately 56,000 people
- Percentage with Usher syndrome, upper limit = 20 per 1,00,000 people (source [5]) , or approximately 2,80,000 people
[2] World Federation of the Deafblind (2018). "At Risk of Exclusion from CRPD and SDG's Implementation: Inequality and Persons with Deafblindness".
[3] National Institute on Deafness and Other Communication Disorders. "Usher Syndrome". [4 to 17 per 100,000 people. Or 0.004% to 0.017%]
[4] Department of Empowerment of Persons with Disabilities. Annual Report 2020-21.
[Total population of India as per 2011 census was 1,210,854,977.
5,033,431 (5M) people had seeing disability ⇒ 0.42% of population.
5,072,914 (5M) people had hearing disability ⇒ 0.42% of population.
The number of deafblind people is unknown because they were counted under the Multiple Disability category.]
[5] Parameswarappa, D.C., et al. (2022). Retinitis pigmentosa in Usher syndrome in India: Electronic medical records driven big data analytics: Report III. Indian Journal of Ophthalmology, 70(7), 2540-2545.
[Reports a hospital-based prevalence rate of 0.02% or 20 per 100,000 people as having Usher syndrome.
For the estimate of the upper limit for India, we chose to use the 0.02% prevalence rate reported in this document, over the 0.017% upper limit suggested in source [3], because of the tendency of Indians to marry within their communities.]
What Are the Symptoms of Usher Syndrome?
Symptoms of Hearing Loss in a Child:
- Does not react typically to loud sounds
- Cannot hear faint sounds
- Does not respond when called by name
- Misunderstands or misses spoken language
- Delayed speech and/or language development for their age, even with speech therapy
- Misunderstands or misses spoken language, especially when unable to see lips
- Struggles to understand conversations with background noise
If your child exhibits symptoms of hearing loss, consult an ENT specialist or an audiologist.
Symptoms of Retinitis Pigmentosa in a Child:
- While walking, cannot see obstacles or people until they are very close
- Frequently bumps into objects or people; appears clumsy or accident-prone- Has blind spots in peripheral vision (e.g. doesn't notice objects or people to their left or right)
- Difficulty seeing in low light, at night, or in dark rooms (e.g. cannot see bright stars at night)
- Takes longer for eyes to adjust when moving from bright to dark areas or vice versa
- Sensitive to glare (e.g. easily gets headaches due to glare)
- Sees halos around lights
- Trips or stumbles over items directly in front of them
- Difficulty seeing the classroom board clearly
- Squints when watching TV
- Holds mobile devices very close to their eyes
If your child already uses hearing aids or cochlear implants and shows signs of vision deterioration, consult a retina specialist or an eye doctor who focuses on inherited retinal diseases (IRDs). Mention that your child has hearing loss and uses hearing aids or cochlear implants during the eye checkup.
If the retina specialist suspects Usher syndrome or another genetic condition, they will perform several tests and may recommend genetic testing.
For Usher syndrome types 1 and 3, balance issues may also be present. Here are some signs of balance problems in a child:
Symptoms of Balance Problems in a Child:
- Delayed sitting, standing, and walking for their age
- Difficulty walking or running in a straight line
- May be perceived as clumsy
How does Usher Syndrome Affect the Body?
The answer is provided here.
Is Usher Syndrome Inherited? What is the Usher syndrome inheritance pattern?
Usher syndrome is an inherited condition, which means it is passed from parents to child through genes.
Usher syndrome has an "autosomal recessive" inheritance pattern. "Autosomal inheritance" means males and females have equal chance of inheriting an Usher gene. "Recessive inheritance" means if a person inherits 2 copies of the same Usher gene (one copy from each parent), then the symptoms of Usher will develop in that person.
If a person has 2 copies of an USH gene (e.g. USH2A) , that person will develop symptoms of Usher syndrome. Also, that person can pass on the USH gene to his/her children.
If a person has 1 copy of an USH gene, that person is called a "carrier", and will not develop symptoms of Usher. However, that person can pass on the USH gene to his/her children.
If two carriers of the same Usher gene have a child together, there is
- a 25% chance with each pregnancy that their child will inherit 2 copies of the USH gene, and will have Usher;
- a 50% chance with each pregnancy that their child will inherit 1 copy of the USH gene, will not develop symptoms of Usher, but will be a carrier; and
- a 25% chance with each pregnancy that their child will not inherit the USH gene
If two people with the same Usher subtype have a child together, there is 100% chance that their child will have Usher.
Because of this inheritance pattern, people who suspect that they have Usher syndrome, or are carriers of Usher syndrome, may choose to consult a genetic counselor before starting a family.
In india, where many people choose to marry within their own community, the lack of awareness about Usher syndrome, or the lack of proper diagnosis, could result into families with many generations having Usher syndrome.
How to Test for Usher Syndrome?
The answer is provided here.
How much does an Usher Syndrome genetic test cost in India?
As of 2019, Medgenome charged 19,500rs for an Usher Syndrome genetic test (to determine the presence of Usher and determine the specific type of Usher). After a positive Usher result was given, they charged 9,700rs for other family members (like siblings) to be tested for that specific Usher type.
There are many possible genetic causes of deafblindness. Talk to your retina specialist to determine which type of genetic test you should get. The Usher syndrome genetic test will only test for the presence of genes related to Usher syndrome. There are broader genetic tests which can detect genes associated with various causes of deafblindness.
The number of genetic testing labs in India is increasing. The test cost mentioned here is just for reference. It is best to call the labs and ask for their prices.
Are There Prenatal Tests for Usher Syndrome?
The answer is provided here.
Currently, we do not know if prenatal tests for Usher syndrome is available or even legal in India.
How to Diagnose Usher Syndrome?
The answer is provided here.
Why is Early Detection and Intervention of Usher Syndrome Important?
The answer is provided here.
Is Usher Syndrome Curable?
The answer is provided here.
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