![]() In other types of Usher’s disease, visual and auditory disorders develop later and are less pronounced vestibular syndrome is not noted. In some cases, there may be cognitive deficits, psychoses. There are vestibular disorders: dizziness, imbalance, atactic gait. This is manifested by difficulty in orientation in the dark, frequent stumbling, collisions with an obstacle (another person, a doorway, furniture). At preschool age, visual dysfunction is detected: as a result of the aggravation of retinitis pigmentosa, peripheral vision rapidly deteriorates, night blindness (hemeralopia) develops. There is a delay in psychomotor development, children start walking late. Already in early childhood, a child is diagnosed with severe sensorineural hearing loss or complete deafness. The classical clinical picture develops with the 1st type of Usher syndrome. ![]() Caused by defects in the genes HARS, PDZD7, CEP250, C2orf71, X-linked can be inherited. It proceeds with a gradual deterioration of hearing and vision, often with vestibular dysfunction. ![]() Associated with mutations of the CLRN1 gene. It is diagnosed in about 60% of patients. It is accompanied by non-progressive hearing loss, visual impairment after 10 years. Caused by mutations USH2A, DFNB31, ADGRV1. Vestibular disorders and signs of retinitis pigmentosa develop up to 5 years. Congenital deafness or deep hearing loss is characteristic. Is associated with mutations in the genes MYO7A, CDH23, PCDH15, USH1G, USH1C. There are 4 clinical subtypes that differ in molecular genetic mechanisms, age of manifestation and severity of symptoms: Usher syndrome is genetically heterogeneous. Pathology also affects the structures of the inner ear: there is atrophy of the spiral node, nerve fibers of the cortical organ, the vascular strip of the cochlea. Over time, there is a narrowing of the fields and a decrease in visual acuity. With Usher syndrome, pigment granules accumulate on the fundus, which spread from the center to the periphery. Genetic mutations lead to a violation of the formation of the perceiving apparatus – photoreceptors and hair cells, which is accompanied by congenital or early debuting disorders of visual, auditory and vestibular function. Protein products encoded by these genes are directly involved in the development and functioning of the receptor apparatus of the retina and inner ear. Representatives of closed ethnic groups are more often ill, among which closely related marriages are quite frequent. Usher syndrome is inherited autosomal recessive from both parents who are carriers of defective genes. CDH23 – “deafness gene”, encodes the protein cadherin-23.The most common mutations are found in the following genes: All these genes, despite their different localization and function, are part of a transmembrane protein complex involved in the movement of myosin, the functioning of retinal photoreceptors, as well as snail hair cells. CausesĬurrently, more than a dozen genes are known whose defects can lead to the development of Usher syndrome. The molecular genetic mechanisms of the syndrome were deciphered in 1995, which opened up wide opportunities for its study. Usher, who in 1914 pointed out the hereditary nature of the disease. However, the syndrome got its “name” in honor of the British optometrist Ch. The “discoverer” of the disease is the German ophthalmologist A. The greatest incidence is observed among Ashkenazi Jews, French Canadians, Spanish Argentines, Finns, etc. Its prevalence in the population is estimated at 3.2-6.2 cases per 100 thousand population (according to other data – 1:6000). Usher syndrome (Usher syndrome) is the most common cause of hereditary deafness.
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