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Usher's syndrome is a hereditary disease that manifests itself in the form of complete deafness from birth, as well as progressive blindness with age. Loss of vision is associated with pigment retinitis - this is the process of pigmentary degeneration of the eye retina. Many people with Usher syndrome also have serious problems with balance.
Due to the research, it was easy to establish that about 8% of the deaf-mute children examined were sick with Usher syndrome (testing was conducted in special institutions for deaf-mute people). Pigmented retinitis was observed in 6-10% of patients with congenital deafness, which in turn is observed in about 30% of people with retinitis pigmentosa.
It is believed that this disease manifests itself in about 3-10 people from 100 thousand around the world. It can be observed in women and men alike. This syndrome affects about 5-6% of the world's population. About 10% of all cases of pediatric deep deafness occur due to Usher I syndrome, and also type II.
In the United States, 1 and 2 types are the most common types. Together, they account for approximately 90 to 95 percent of all cases of Usher's syndrome in children.
Causes of the usher syndrome
Usher's syndrome I, II, and also III types carries an autosomal recessive cause, but type IV is considered a violation of the X chromosome. The causes of this syndrome of blindness, as well as deafness, have not been sufficiently studied. It is assumed that people with this disease are hypersensitive to components that can damage the structure of DNA. With this disease, disorders of the immune system can also be associated, but in this case there is no precise picture of such a process.
In 1989, patients with type II disease were first diagnosed with chromosomal abnormalities, which could subsequently lead to a way of isolating genes that trigger the development of the syndrome. In addition, it will also be possible to identify these genes from their carriers and develop special antenatal genetic tests.
Inheritance of the syndrome occurs in the case when both parents are ill, that is, the inheritance is a recessive type. A child can also inherit a disease in the event that his parents are carriers of the gene. If both future parents have this gene, the probability of having a baby with this syndrome is 1 to 4. A person who has only one gene of the syndrome is considered to be a carrier, but he himself does not have the symptoms of the disorder. Today it is not yet possible to determine whether a person has a gene for this disease.
If the child is born to parents, one of whom does not have such a gene, then the probability that he will inherit the syndrome is very low, but he will be unequivocal carrier.
Symptoms of the usher syndrome
Symptoms of Usher's syndrome are hearing loss, and besides this pathological accumulation of pigmented cells in the eye structures. Further, the patient develops degeneration of the eye retina, because of what begins deterioration of vision with the subsequent loss of it in the most severe case.
Sensorineural hearing loss is mild or complete and usually does not progress from birth. But retinitis pigmentosa can begin to develop in childhood or later. The results of the survey showed that the acuity of central vision can persist for many years, even when peripheral vision deteriorates (this condition is called "tunnel vision").
These are the main manifestations of the disease, which can sometimes be supplemented by other disorders - such as psychosis and other mental disorders, problems with the inner ear and / or cataracts.
During the research, 3 types of this disease were identified, and also 4 forms-quite rare.
I type of disease is characterized by congenital complete deafness, as well as a balance disorder. Often, these children begin to walk only at the age of 1.5 years. Deterioration of vision usually begins with 10 years, and the final development of the state of night blindness begins with 20 years. Children with this type of disease can develop progressive deterioration of peripheral vision.
With type II disease , moderate or congenital deafness is observed. Often, in this case, deterioration with partial deafness no longer occurs. Pigment retinitis begins to develop around the end of the adolescent period or after 20 years. The development of night blindness usually begins in the 29-31 year. Disturbances in visual acuity in case of type II pathology basically progress slightly more slowly than in type I.
III type of the disease is characterized by a progressive loss of hearing, usually beginning during puberty, and also by the gradual appearance in the same period (slightly later than the hearing loss) of retinitis pigmentosa, which can become a factor in the development of progressive blindness.
Manifestations of the fourth type of pathology mainly occur in males. In this case, there are also progressive disorders and loss of hearing and vision. This form is very rare and usually has an X-chromosome nature.
Diagnostics of the usher syndrome
Diagnosis of Usher's syndrome is made on the basis of the patient's combination of sudden deafness with progressive loss of vision.
To detect a mutation, a special genetic test can be assigned.
11 genetic loci were found that can cause the development of Usher's syndrome and identified nine genes that are exactly the cause of the disorder:
- Type 1: MY07A, USH1C, Cdh23, Pcdh15, SANS.
- Type 2: ush2a, VLGR1, WHRN.
- Type 3 Ushira syndrome: USH3A.
NIDCD scientists together with colleagues from universities in New York and Israel identified a mutation called R245X of the Pcdh15 gene, which is a large percentage of the 1 type of Usher syndrome among the Jewish population.
To find out about laboratories that conduct clinical trials, visit https://www.genetests.org and search the laboratory research catalog by typing the term "Usher syndrome."
To find out about existing clinical trials that include genetic testing for Usher's syndrome, visit the https://www.clinicaltrials.gov website and enter "genetic test" in the search "Usher syndrome" or "Usher's syndrome."
There are several methods of instrumental diagnostics:
- Examination of the fundus to identify the presence of retinas on the retina, as well as the narrowing of the retinal vessels;
- Electroretinogram, which allows you to identify the initial degenerative abnormalities in the eye retina. It shows the extinction of electro-radiographic paths;
- Electronystagmogram (ENG) measures involuntary eye movements, which could indicate the presence of imbalance
- Audiometry, which determines the presence of deafness and the degree of its severity.
Usher's syndrome must be differentiated with some similar abnormalities.
The syndrome of Hallgren, in which congenital hearing loss is observed, as well as progressive loss of vision (cataracts and nystagmus also appear). Among the additional symptoms of the disease: ataxia, psychomotor disorders, psychosis and mental retardation.
Alstrom's Syndrome, which is a hereditary disease in which retinal degeneration occurs, as a result of which central vision is lost. This syndrome is associated with the problem of childhood obesity. In this case, diabetes mellitus and hearing loss begin to develop after 10 years.
Rubella in a pregnant woman in the first trimester can cause a variety of abnormalities in the development of the child. Among the consequences of this anomaly is hearing loss, as well as (or) problems with eyesight, and besides this, various developmental defects.
Treatment of the usher syndrome
To cure Usher's syndrome is now impossible. Therefore, the therapy in this case is mainly to slow the process of falling vision, and also to compensate for hearing loss. Possible treatments include:
- The use of vitamin A group (some ophthalmologists believe that high doses of vitamin A palmitate may slow down, but not stop, the progression of pigment retinitis);
- Implantation of special electronic devices in the auricles of the patient (auditory apparatus, cochlear implants.
Ophthalmologists recommend that most adult patients with advanced forms of retinitis pigment take 15,000 IU (international units) of vitamin A daily in the form of palmitate under supervision. Since people with type 1 Usher syndrome did not participate in the study, high doses of vitamin A are not recommended for this group of patients. People who are considering taking vitamin A should discuss this option with their doctor. Other recommendations regarding this treatment option include:
- Change your diet with the inclusion of foods high in vitamin A.
- Women who plan pregnancy should stop taking high doses of vitamin A three months before the planned conception because of the increased risk of birth defects.
- Women who are pregnant should stop taking high doses of vitamin A due to an increased risk of birth defects.
It is also important to adapt such a child to social life. This requires the help of educators-defectologists, as well as psychologists. In the case when the patient has begun a progressive fall in vision, one should teach him to use sign language.
Usher's syndrome has an unfavorable prognosis. The field of vision and its severity begin to deteriorate in the period of 20-30 years in the majority of patients with this disease of any type. In some cases, it comes to a complete bilateral loss of vision. Deafness, which is always observed and dumbness, very quickly develops to full bilateral loss of hearing.