Understanding Usher Syndrome | Ophthalmology

Usher Syndrome

What is usher syndrome?

Usher syndrome is a rare genetic disorder that can transmit sensory information (sound) to the brain due to the impaired capacity of the inner ear and auditory nerve (sensorineural hearing loss). Retinitis affects the retina and causes progressive vision damage. The age at which symptoms appear and the severity of the symptoms that distinguish the different types of Usher syndrome are determined by the underlying genetic cause.  

Usher syndrome was first described by Albrecht von Graf in 1858 but was named after Charles asher, a Scottish ophthalmologist who identified the inherited nature of the disorder and its recessive pattern.

Types of usher syndrome

Type 1

Children born with type 1 Usher syndrome:

  • Almost completely deaf at birth
  • There are serious balance problems
    • Sit up unsupported at an earlier age than normal (usually 6 to 9 months of age)
    • Late walkers (18-24 months)
  • Usually, in childhood, he develops vision problems before the age of 10
    • The night begins with vision problems
    • Quickly progress to total blindness
  • You may not benefit from headphones (speakers). They may be candidates for cochlear implants (a surgically placed device that sends sound directly from the ear to stimulate the auditory nerve).

Type 2

Children born with Usher syndrome type 2:

  • You have a severe hearing loss at birth
  • Have a normal balance
  • You can benefit from hearing aids
  • Developing night vision problems during adolescence
    • Progress more slowly
    • It is not the cause of total blindness

Type 3

Children born with Usher syndrome type 3:

  • The normal hearing at birth.
  • Have an almost normal balance
    • Sometimes there are balance problems later on
  • A gradual loss of hearing and vision
    • The rate of damage varies in children
    • Hearing loss is evident in teens
  • Hearing aids can benefit from the onset of hearing loss
  • Night blindness begins in adolescence
    • Blind spots occur in the late teens or early teens
    • Total blindness in middle age

Causes of usher syndrome

Usher syndrome gives rise to mutations in specific genes. To date, Usher syndrome has been associated with mutations in at least ten genes:

Usher syndrome type 1: MYO7A (USH1B), USH1C, CDH23, PCDH15 (USH1F), SANS (USH1G), and possibly CIB2

Usher syndrome type 2: USH2A, ADGRV1 (formerly known as VLGR1) WHRN (DFNB31)

Usher syndrome type 3: USH3A (CLRN1), HARS

These genes provide instructions for making proteins for normal hearing, vision, and balance. Some of these proteins help specific cells called hair cells transmit sound from the inner ear to the brain and absorb light and color in the retina of the eye. The function of some proteins produced by genes associated with Usher syndrome is unknown.

Some people with Usher syndrome do not have mutations in any of these genes, so other genes associated with the condition have not yet been identified.

All types of Usher syndrome are inherited as autosomal recessive symptoms. Most genetic diseases are determined by the state of two copies of a gene, one from the father and the other from the mother. When a respective inherits two copies of an irregular gene for the same trait, one from each parent. If a person inherits a normal gene for a disease and a gene, that person is a carrier for the disease, but usually shows no symptoms. There is a 25% risk that two carrier parents with each carrier will outgrow a mutated gene and have an affected child. The danger of having a child who is a carrier like the parents is 50% with each pregnancy. Children have a 25% chance of inheriting genes from their parents. The risk is the same for men and women.

Both are more likely to carry the same abnormal gene than parents who are not close relatives (consonant), increasing the risk of having children with a regressive genetic disorder.

Symptoms of usher syndrome

Usher syndrome is a condition in which the brain can transmit sensory information (sound) (sensorineural hearing loss) due to the weakened capacity of the inner ear and auditory nerve (as well as an abnormal accumulation of pigment) in the membrane that covers the nerve. (Retina) that lines the eyes (retinitis pigmentosa or RP). RP can eventually lead to retinal degeneration, which can lead to progressive loss of vision and legal blindness. Sensorineural nerve deafness can be profound or mild and progressive. Vision loss caused by RP begins in childhood or later in life and is often difficult to see at night or in low light (“night blindness”). Studies show that clear central vision can persist for many years, even if the side (peripheral) vision is reduced. These narrow visual fields are also known as “tunnel vision.” People with Usher syndrome type 1 and 3 have balance problems.

This disorder is characterized by profound hearing loss (congenital deafness) and balance problems in both ears at birth. In most cases, affected children do not learn to walk until they are 18 months or older. Although some parents report that it begins in children under the age of 10, vision problems generally begin around the age of ten. Usher syndrome type 2 is characterized by mild to severe hearing loss in both ears at birth. In some cases, hearing loss can get worse over time. Night blindness begins in your late teens or early twenties. Loss of peripheral vision persists, but central vision is usually present in adolescence. The visual problems associated with Type 2 Usher syndrome progress more slowly than those associated with Type 1.

This disorder is characterized by early hearing loss after type 3, variable (vestibular) balance dysfunction, and RP that can manifest between the second and fourth decades. Balance problems occur in about 50% of people with type 3 Usher syndrome.

Risk factors

Usher syndrome is more common in people whose parents or parents carry the wrong gene.

Diagnosis of usher syndrome

Since Usher syndrome cannot currently be cured, it can help to better identify children before they develop night blindness. Some basic studies suggest that 10% of children who are deaf at birth may have Usher syndrome. However, misdiagnosis can have bad consequences.

The easiest way to diagnose Usher syndrome is to perform a chromosome mutation test. An alternative approach is electrocardiography, which is often unpleasant for children because even their discomfort makes the results unreliable. . Usher syndrome may be prescribed if the child is very deaf from birth and walks slowly.

Others include Alport syndrome, Alstrom syndrome, Bardet-Beadle syndrome, cocaine syndrome, congenital spondylolisthesis dysplasia, Flynn-Aird syndrome, Friedrich ataxia, Harler syndrome (MPS-1 ), and Kear’s syndrome. (CPEO), Nori syndrome, osteopetrosis, Refsum disease (phytanic acid storage disease), and Zellweger syndrome.

Treatment for usher syndrome

Loss of the Usher syndrome gene can be reduced by gene therapy (“genetic recombination”) that replaces the proper protein if the excess protein becomes functional. Recent studies of mouse models have shown a variant of the disease, which is associated with a mutation in myosin VIIa, which can be alleviated by altering the mutation gene using lentivirus. Proteins, which contain approximately 6000 amino acid residues. Gene replacement therapy for such large proteins can be difficult.

The treatment of Usher syndrome is directed to specific symptoms that are evident in each individual. Such treatment may include pediatricians or interns, specialists in the evaluation and treatment of hearing and balance deficiencies (otolaryngologists and audiologists), ophthalmologists, and/or other healthcare professionals.

Sensorineural deafness should be assessed and communication options explored as soon as possible to provide children with a clear linguistic foundation. Hearing aids or cochlear implants can benefit many babies and children with this disorder. American Sign Language can be explored as a communication option. People who perform visual cues when vision is reduced often switch to tactile cues. Early intervention is important for children with this disorder to reach their potential. Beneficial services may include specialized services for sensorineural deafness or deafblindness and other medical, social, and/or professional services.

There is currently no known treatment for RP, although researchers are working to repair or reverse vision loss related to RP through gene and other therapies. Some researchers have shown that taking a specific daily dose of vitamin A can slow the progression of retinal degeneration in people with typical RP and type 2 Usher syndrome. Some experts recommend that adult patients with generalized RP take 15,000 IU of the vitamin. A day. Palmitate under the care of your ophthalmologists, follow a regular balanced diet and avoid an overdose of vitamin E. Chronic high-dose supplementation of vitamin A (eg, more than 25,000 IU) can cause some adverse effects, such as liver disease, and the doctor should monitor patients regularly when taking such a supplement.

People with RP with this disorder may find low vision aids helpful. Another treatment for Usher syndrome is symptomatic and adjuvant. Agencies that serve people with hearing and visual disabilities can help.

Prevention

Currently, there is no treatment to prevent. slow the progression of, or inhibit the transmission of Usher syndrome. Cochlear implantation is a viable, proven option for individuals with Usher syndrome.

Departments to consult for this condition

  • Department of Ophthalmology
Share on facebook
Facebook
Share on google
Google+
Share on twitter
Twitter
Share on linkedin
LinkedIn
Share on pinterest
Pinterest

Leave a Reply

Your email address will not be published. Required fields are marked *