Understanding Usher Syndrome Type 1B

Defining Characteristics & Research Significance

Being born severe to profoundly deaf or gradually losing hearing, losing vision starting in infancy or later in adolescence, and being born with severe balance problems are the three conditions that people with Usher syndrome look for according to the type (1, 2 or 3) they suffer from.

Usher syndrome is the most common cause of deafblindness in children. It represents between 3 and 6% of all childhood deafness. 50% of people with deafblindness in developed countries are due to this syndrome. Its estimated prevalence ranges between 6-17/100,000.

Usher syndrome is a rare genetic condition first described in 1858. It is an autosomal recessive hereditary disorder, thus inherited from parents to children, which only manifests itself in 25% of cases in which both parents are carriers of the mutation.

Usher syndrome is characterized by affecting three main senses: hearing, vision and balance.

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Bilateral congenital profound deafness

Rapid vision loss

Lack of vestibular function

Children are born profoundly deaf. Cochlear implants are a solution for these children to have access to hearing and verbal communication.

The speed at which vision loss progresses is faster than other types. Individuals with USH1 mutations reach legal blindness on average 15 years earlier than other types. Significant vision loss often happens before puberty, starting with a complete loss of night vision between the ages of 3-5 and accelerated peripheral vision loss during day light, all due to Retinitis Pigmentosa (RP).

Type 1 (and 50% of type 3 cases) is characterized by lack of balance due to a nonfunctioning vestibular system (the semicircular canals in the inner ear). This involves a delay in acquiring the sitting position, in starting to walk, as well as in all physical childhood activities (jumps, races, games…). Balance issues persist throughout life affecting individuals overall mobility. This lack of balance can be compensated by different inputs: vision and proprioception (body contact with surfaces): so as visual acuity decreases due to the progression of Retinitis Pigmentosa, balance problems can intensify.

There are three types of Usher syndrome according to their severity: type 1, 2 and 3

Type 1 is the most severe and profoundly affects hearing and balance from birth, and vision during childhood. Types 1 (and 3) experiment severe balance problems due to vestibular dysfunction. Type 2 is slower in progression, with individuals losing hearing and vision later in life.

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