What are the other Names for this Condition? (Also known as/Synonyms)

• USH3 (Usher Syndrome Type 3)
• USH3A
• Usher Syndrome Type III

What is Usher Syndrome Type 3? (Definition/Background Information)

• Usher Syndrome is a genetic disorder characterized by sensorineural hearing loss or deafness and progressive vision loss due to retinitis pigmentosa
• Three major types of Usher syndrome have been described - types I, II, and III. The different types are distinguished by their severity and the age when signs and symptoms appear
• All three types are inherited in an autosomal recessive manner 
• Treatment for the hearing loss may include hearing aids or surgery for a cochlear implant

(Source: Usher Syndrome Type 3; Genetic and Rare Disease Information Center (GARD) of National Center for Advancing Translational Science (NCATS), USA.)

• Most cases of Usher Syndrome Type 3 (USH3) are caused by mutation(s) in the CLRN1 gene

Who gets Usher Syndrome Type 3? (Age and Sex Distribution)

• Usher Syndrome Type 3 is a rare congenital disorder; it accounts for 2% of all Usher syndrome cases
• The presentation of symptoms begins later in life, typically in late childhood or adolescence
• Both males and females may be affected
• Usher Syndrome is common in Finland and among the Ashkenazi Jewish population, accounting for about 40% of all cases

What are the Risk Factors for Usher Syndrome Type 3? (Predisposing Factors)

• A positive family history may be an important risk factor, since Usher Syndrome Type 3 can be inherited

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Usher Syndrome Type 3? (Etiology)

• Usher Syndrome Type 3 is caused by mutation(s) in the CLRN1 gene. This gene codes for a protein that is important for the functions of hearing, vision, and balance
• CLRN1 gene mutations are inherited in an autosomal recessive manner

Autosomal recessive mode of inheritance: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Usher Syndrome Type 3?

The signs and symptoms of Usher Syndrome Type 3 may include:

• Retinitis pigmentosa leading to impaired vision
• Hearing loss
• Problems with balance

How is Usher Syndrome Type 3 Diagnosed?

Usher Syndrome Type 3 is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests
• Imaging studies
• Biopsy studies, if necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Usher Syndrome Type 3?

The complications of Usher Syndrome Type 3 may include:

• Permanent loss of vision
• Deafness
• Risk of falls and injuries due to loss of a sense of balance

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Usher Syndrome Type 3 Treated?

• There is no cure for Usher Syndrome Type 3, since it is a genetic condition. The treatment is usually given to manage the signs and symptoms and any complication that develops
• Hearing aids may be recommended for impaired hearing
• Cochlear implantation surgery may be recommended for hearing loss 

How can Usher Syndrome Type 3 be Prevented?

Usher Syndrome Type 3 may not be preventable, since it is a genetic disorder.

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy), if available, may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders
• Regular medical screening at periodic intervals with tests and physical examinations are recommended

What is the Prognosis of Usher Syndrome Type 3? (Outcomes/Resolutions)

• The prognosis of Usher Syndrome Type 3 is dependent upon the severity of the signs and symptoms and associated complications, if any
• In most affected individuals, the symptoms worsen over time such that profound vision and hearing loss ensue

Additional and Relevant Useful Information for Usher Syndrome Type 3:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/