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

• USH2C (Usher Syndrome, Type 2C)
• Usher Syndrome, Type IIC

What is Usher Syndrome, Type 2C? (Definition/Background Information)

• Usher Syndrome is a group of disorders characterized by hearing loss and compromised vision
• Usher Syndrome, Type 2C (USH2C) is caused by a mutation in the ADGRV1 gene (also known as GPR98 or VLDR1), or digenic mutations in ADGRV1 and PDZD7 genes 
• USH2C is characterized by moderate to severe hearing loss and compromised vision in affected males and females
• The treatment for Usher Syndrome, Type 2C is geared toward managing the signs and symptoms of the disorder
• The prognosis is determined by the severity of vision impairment, with the majority of affected individuals losing vision between 50-70 years of age

Who gets Usher Syndrome, Type 2C? (Age and Sex Distribution)

• Usher Syndrome, Type 2C is a rare congenital disorder. The presentation of symptoms may occur at birth
• Both males and females may be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Usher Syndrome, Type 2C? (Predisposing Factors)

• A positive family history may be an important risk factor, since Usher Syndrome, Type 2C can be inherited
• Currently, no other risk factors have been clearly identified for the syndrome

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 2C? (Etiology)

• Usher Syndrome, Type 2C is caused by a mutation in the ADGRV1 gene; the gene is also known as the GPR98 or VLDR1 gene
• USH2C may also be caused by mutation(s) in two different genes namely, the ADGRV1 and PDZD7 genes
• Usher Syndrome, Type 2C is inherited in an autosomal recessive manner

Autosomal recessive: 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 2C?

The signs and symptoms of Usher Syndrome, Type 2C may vary in severity among the affected individuals, and include:

• Hearing loss before onset of speech (predominantly high frequency loss not associated with vestibular disorders)
• Retinitis Pigmentosa with symptoms that include:
• Impaired vision in low lighting conditions
• Loss of function of rod photoreceptor cells, leading to night blindness
• Peripheral vision loss (only in low-light settings in earlier stages), resulting in tunnel vision
• Decreased contrast sensitivity
• Progressive loss of visual field
• Decreased visual acuity and color vision in later stages
• A small amount of central vision may only remain during the later stages (as if looking through a peephole)
• Difficulties in speech development

How is Usher Syndrome, Type 2C Diagnosed?

Usher Syndrome, Type 2C is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Tests to assess and ascertain hearing loss, which may include:
• Otoscopy: Examination using an instrument that allows the physician to look inside the ear
• Weber test: A test in which a vibrating tuning fork is placed on the midline of the head
• Rinne test: A test in which a vibrating tuning fork is held next to the ear and then in front of the ear, until the individual no longer hears the sound
• Audiometric test: Hearing tests that involve listening to different tones
• Tympanometry: A test involving air pressure in the ear canal to measure eardrum mobility (movement)
• Acoustic reflex: A test that stimulates the stapedius (a tiny ear muscle) to move, in response to a loud sound
• Vision acuity tests
• Thorough examination of eyes: When a healthcare professional examines the eye using specialized instruments, the following signs may be noted:
• Clumped pigment in the peripheral and mid-peripheral retina, also known as bone-spicule pigmentation
• Small blood vessel attenuation
• Waxy appearance of the optic nerve
• 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 2C?

The complications of Usher Syndrome, Type 2C may include:

• Complete hearing loss
• Speech impediment
• Blindness

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

How is Usher Syndrome, Type 2C Treated?

The management of Usher Syndrome, Type 2C requires a multidisciplinary team with experience in the management of combined deafness and blindness (ENT specialist, ophthalmologist, speech therapist, psychologist, hearing aid specialist, psychomotor development programs, and adapted learning programs for patients with both hearing and visual deficits).

• Conventional hearing aids may be indicated for patients with moderate to severe hearing loss
• Cochlear implants, unilateral or bilateral, are now more frequently used for patients with profound congenital hearing loss
• Both cochlear implants and hearing aids are more effective when implemented early
• Lenses with specialized filters may be recommended for management of retinopathy
• Current research is directed towards gene therapy, neuroprotection and artificial vision systems

(Source: Usher Syndrome; Orphanet, National Institute of Health and Medical Research (INSERM), Paris.)

How can Usher Syndrome, Type 2C be Prevented?

Usher Syndrome, Type 2C 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) 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 2C? (Outcomes/Resolutions)

• The prognosis of Usher Syndrome, Type 2C mainly depends on the progression of the visual loss
• Blindness occurs in almost all cases between 50 and 70 years of age

(Source: Usher Syndrome; Orphanet, National Institute of Health and Medical Research (INSERM), Paris.)

Additional and Relevant Useful Information for Usher Syndrome, Type 2C:

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

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