Associated Conditions

Click on the following links to find out more about each of these conditions

USHER SYNDROME 

Symptoms and Cause 

This genetic condition causes hearing loss from birth and progressive loss of sight due to retinitis pigmentosa (RP), which causes degeneration of the retina. Often the first symptom of RP is night blindness, followed by narrowing side vision leading to what is called "tunnel vision".

Three types of Usher syndrome

In Usher Syndrome Type 1, there is severe damage to the cochlea from a very early age and therefore the child has severe deafness from birth. The child usually develops problems with night vision and tunnel vision due to RP in the first 10 years of life.

People with this condition usually communicate by signing. This clearly can become more difficult as vision deteriorates.

In Usher Syndrome Type 2, the hearing loss is more variable, ranging from mild to severe. Symptoms of RP usually develop from late adolescence to late twenties. Communication is enhanced in these people with hearing aids and lip reading.

With Usher Syndrome Type 3, the person is born with normal hearing and close to normal balance.  The loss of hearing becomes more pronounced as the person gets older.  Measurable hearing loss occurs by puberty. Vision loss starts to develop during the teenage years and may progress during life.  Balance deteriorates as the person gets older.  The majority of people with US3 live in Finland.

LARA'S STORY

Lara has been diagnosed with Usher Syndrome Type 2. Lara is currently studying meetings and events management, and is planning a career in media, focusing on motivational speaking.
	Copyright Studio One Photographics

Diagnosis

It is important to consider Usher syndrome in any child who is having considerable hearing problems, since this may be evident before the symptoms of RP develop. A common early symptom may be the delayed development of speech. Early diagnosis in children is important so that a child's educational needs can be met, and career choices made.
Figures from the USA and Scandinavia suggest that 3 to 6% of all people born deaf have this condition. In Victoria, a recent survey of people with RP showed that 8% have Usher syndrome.

Diagnosis will normally include the following:

Assessment by an ear, nose and throat specialist to ensure correct diagnosis of the hearing loss.

Assessment by an ophthalmologist to assess the presence and severity of RP.

Special hearing and vision tests (such as ERG) to confirm the diagnosis. (An Electro Retinogram (ERG) measures the electrical activity in the retina. A person with RP has a significantly abnormal ERG).

Genetic factors

This disease is a genetic autosomal recessive disorder.

 Click here for Inheritance Patterns

Living with Usher syndrome

Loss of both sight and hearing affects communication, mobility and daily living. It can make independent living more difficult to achieve.

We depend on sight and sound to communicate. People with Usher syndrome depend more on their sight for communication, lip-reading and reading sign language. The effects of vision loss can cause serious problems in communication, particularly in poor light.

Members of both the vision impaired and hearing impaired communities need to be aware of this condition to provide support to those members of their communities who have this condition.

Special consideration and understanding is important because both senses of vision and hearing are affected to a greater or lesser degree. Advice about mobility and supporting aids may need to the modified to ensure maximum benefit.

These issues also need to be considered by medical and other people who provide advice and care for people with Usher syndrome.

Support services

With the appropriate support, training and aids, people with Usher syndrome can live independently. Services for a person with Usher syndrome will depend on age and severity of the hearing and vision problems, but will normally include the following types:

• Genetic counselling

• Audio logical support, including fitting of hearing aids when necessary.

• Educational training that, at different ages, may include: 

• preschool and school assessment and placement,
  independent living training, and/or career guidance.
  Rehabilitation counselling that may include: 

• family support, orientation and mobility training, and/or
  communication aids.

• The state branches of the Deaf-Blind Society and Deaf and Blind Children's Institute should also be contacted.

Ear Anatomy and Physiology

Structure and function of the ear

• auricle - the outer part of the ear, situated on either side of the head.
  ear canal - lined with skin, it passes from the hole in the auricle through cartilage and bone to the tympanic membrane (ear drum).

• tympanic membrane - the thin transparent piece of skin at the end of the ear canal.

• outer ear - the auricle, ear canal and outer surface of tympanic membrane.

• middle ear - a small air-filled bony chamber that contains three small bones connecting the tympanic membrane to the inner ear.
  inner ear - This consists of two parts:

• cochlea - a small shell-shaped, fluid-filled structure with many small hairs along its length

• semi circular canals - structures filled with fluid.

• vestibulo-cochlear nerve - connected to both the cochlea and semi circular canals, it connects the inner ear to the brain.

Function of the ear

When a trumpet produces a sound, it sets up vibrations (in the air) that are trapped by the auricle, and conducted to the tympanic membrane, that then vibrates. This causes movement of the three small bones in the middle ear that, in turn, transmit the vibrations to cause ripples in the cochlear fluid. These stimulate the hairs to move, thereby affecting the vestibulo-cochlear nerve that sends messages to the brain that recognises the sound as a trumpet blowing. Higher pitched sounds cause more hairs to vibrate than do the lower sounds.

The semi circular canals respond to changes in body position and send messages to the brain, thereby helping to control balance.

For unknown reasons, people with Usher syndrome become deaf because damage occurs to the hair cells that vibrate in the cochlear fluid. This damage may increase with age. Thus, when a sound is made near the auricle, it will pass through the canal to the middle ear. However, subsequent transmission of the sound to the cochlea will be faulty and hence the sound will be inadequately passed along the vestibulo-cochlear nerve or recognised by the brain.

Syndromes that affect vision and other bodily functions

USHER SYNDROME

People are born deaf or with partial hearing loss, and develop RP in late childhood or early teen years.

BARDET-BIEDL SYNDROME

RP with possible physical abnormality, obesity, kidney disease and mental retardation.

BASSEN-KORNZWEIG SYNDROME

RP with progressive neurological problems.

CHOROIDEREMIA

Choroideremia is a rare inherited disorder that causes progressive loss of vision due to degeneration of the choroid and retina.

CLINICAL DESCRIPTION

Choroideremia occurs almost exclusively in males. In childhood, night blindness is the most common first symptom. As the disease progresses there is loss of peripheral vision or "tunnel vision", and later a loss of central vision. Progression of the disease continues throughout the individual's life, although both the rate and the degree of vision loss are variable among those affected, even within the same family.

Vision loss due to choroideremia is caused by degeneration of several layers of cells that are essential to sight. These layers, which line the inside of the back of eyes, are called the choroid, the retinal pigment epithelium and the photoreceptors. The choroid consists of several blood vessel layers that are located between the retina and the sclera (the "white of the eye"). Choroidal vessels provide the retinal pigment epithelium and photoreceptors with oxygen and nutrients necessary for normal function. The retinal pigment epithelium and the photoreceptors are part of the retina. The epithelium is associated closely with the photoreceptors and is needed for normal function. The photoreceptors are responsible for converting light into the electrical impulses that transfer messages to the brain where "seeing" actually occurs.

Click here for diagram of eye

The retinal epithelium and the choroid initially deteriorate to cause choroideremia. Eventually, the photoreceptors break down as well. As the disease progresses, the clinical appearance of these cell layers changes in a characteristic manner and more vision is lost.

INHERITANCE

Choroideremia is passed to succeeding family generations through the X-linked inheritance pattern. 

Click here for Inheritance Patterns

Occasionally a woman who carries the X-linked choroideremia gene experiences some difficulty with night vision later in life. Only rarely do carriers lose peripheral vision.

TREATMENT

Recently scientists discovered the exact identity of the gene on the X chromosome that causes choroideremia. New research based on these findings now drives the search for a treatment. However, at present there is no effective treatment or cure.

Choroideremia is one of the few retinal degenerative diseases that might be detected prenatally in some cases; female carriers may want to seek information about this from a medical geneticist or a genetic counsellor. All members in affected families are encouraged to consult an ophthalmologist and to seek genetic counselling. These professionals can provides explanations of the disease and the recurrence risk for all family members and for future offspring.

Individuals with choroideremia may benefit from the use of low-vision aids, including electronic, computer-based and optical aids, as well as orientation and mobility training.

RELATED DISEASES

Early in the course of the disease, choroideremia could be confused with the X-linked retinitis pigmentosa. Both have symptoms of night blindness and tunnel vision. However, differences are clear in a complete eye examination, especially as the disease progresses. The disease most similar clinically to choroideremia is gyrate atrophy. It too can be distinguished base on its inheritance as an autosomal recessive disorder and based on its cause, known to be defect in an unrelated gene.

Click here for Genetic Inheritance Patterns

Information about these conditions should be obtained by consulting an ophthalmologist, paediatrician and geneticist.

LAURENCE MOON

Laurence Moon is a more rare, but similar condition to Bardet Biedel with retinal pigmental changes plus progressive neurological changes, and learning difficulties.

Polydactyl is not present.

Laurence Moon and Bardet Biedel are both genetic and there are a number of genes that are currently being investigated.

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