Usher Syndrome: Symptoms, Causes, Treatment

Overview

Usher syndrome is a rare genetic disorder that causes serious hearing loss and an eye disorder retinitis pigmentosa (RP). Usher syndrome is the most common condition that affects hearing and vision, and sometimes it also affects balance.

There are three major types of Usher syndrome, known as types I, II, and III. According to the National Institutes of Health, 3% to 6% of all children who are deaf and 3% to 6% of children who are hard-of-hearing have Usher syndrome. In United States, about four babies in every 100,000 newborns have Usher syndrome.

Types

Researchers have identified three major types of Usher syndrome: types I, II, and III. These types are distinguished by the severity of hearing loss, the presence or absence of balance problems, and the age at which signs and symptoms appear.

Of them, type 1 and type 2 are the most common forms of Usher syndrome in the United States, which together account for about 95% of all cases of Usher syndrome.

  • Type 1: Children with type 1 Usher syndrome are almost totally deaf at birth and have severe balance problems. They also have night vision problems which progress quickly to total blindness.
  • Type 2: Children with type 2 Usher syndrome are born with moderate to severe hearing loss but have normal balance. In most cases, they can communicate orally and benefit from hearing aids. RP progresses more slowly and is usually diagnosed during late adolescence.
  • Type 3: Children with type 3 Usher syndrome have normal hearing and almost normal balance at birth. However, some may develop balance problems with age and have gradual hearing and vision loss. Night blindness also usually begins during adolescence. Blind spots appear by the late teens. Total blindness often occurs by middle age.

Causes

Usher syndrome is inherited. It is passed from parents to children through genes. Usher syndrome is caused by mutations in specific genes. So far, it has been associated with mutations in at least ten genes.

Usher syndrome is an autosomal recessive disorder. It means males and females can both be affected by the condition. Besides, the condition occurs only when a child inherits two copies of the same faulty gene, one from each parent. A person with one abnormal Usher gene does not have the disorder, but there is a 50 percent chance of passing on the abnormal gene to a child.

Symptoms

The symptoms of Usher syndrome vary depending on the type of the condition as is mentioned above. Usher syndrome is mainly characterized by different levels of hearing loss and deafness due to an impaired ability of the inner ear and auditory nerves to transmit sensory input to the brain as well as abnormal accumulation of colored material on the nerve-rich membrane lining the eyes. Balance problems are seen in individuals with Usher syndrome types 1 and 3.

Diagnosis

Diagnosis of Usher syndrome includes asking questions about the patient’s medical history and testing of hearing, balance, and vision. Early diagnosis is important, because it can increase the possibility of treatment success.

  • Hearing testing

Infants born in the United States will have a hearing screen at birth. Those who do not pass the newborn hearing screening should have a follow-up hearing test to evaluate hearing loss.

Besides, genetic testing may be done to find out if they have an Usher syndrome gene, based on additional signs and symptoms.

Teens or young adults with hearing loss should conduct an audiology evaluation. This test measures how loud a sound needs to be before it is heard.

  • Vision testing

Common vision tests include:

Retinal exam. It is used to detect changes in blood vessels, a waxy look to the retina surface, and clumps of dead retinal cells.

Visual field testing. It measures peripheral vision.

Electroretinogram (ERG). An electroretinogram measures the electrical response to the light-sensitive cells in the retina of the eyes. It can confirm the diagnosis of retinitis pigmentosa. In this test, general anesthesia is used for the insertion of a contact lens.

  • Balance testing

Electronystagmogram (ENG) measures involuntary eye movements, which might signify balance problems.

Treatment

Unfortunately, there is no cure for Usher syndrome. However, some supportive treatment options can help relieve the symptoms, which may include hearing aids, assistive listening devices, and cochlear implants. Besides, communication methods such as American Sign Language, orientation and mobility training for balance problems can also help. Communication services and independent-living training include Braille instruction, low-vision services, or hearing training. Individuals with RP associated with Usher syndrome may turn to low-vision aids.

Some researchers have found that taking a specific daily dose of vitamin A can slow the progression of retinal degeneration in some people with typical RP and Usher syndrome type 2. However, long-term high-dose vitamin A supplementation may cause certain adverse effects, such as liver disease, so patients should be regularly monitored by the doctors when taking such supplementation.


Keywords: usher syndrome.

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* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.