Click on the following links to find out more about each of these conditions
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
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.
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.
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.
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).
This disease is a genetic autosomal recessive disorder.
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.
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:
Structure and function of the ear
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
People are born deaf or with partial hearing loss, and develop RP in late childhood or early teen years.
RP with possible physical abnormality, obesity, kidney disease and mental retardation.
RP with progressive neurological problems.
Choroideremia is a rare inherited disorder that causes progressive loss of vision due to degeneration of the choroid and retina.
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.
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.
Choroideremia is passed to succeeding family generations through the X-linked inheritance pattern.
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.
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.
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.
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.
Information about these conditions should be obtained by consulting an ophthalmologist, paediatrician and geneticist.
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.