Usher syndrome, type 1

Other Names: USH1A; Usher syndrome, type 1A; Usher syndrome, type I, French variety; Retinitis pigmentosa and congenital deafness; USH1; US1 Usher syndrome is a genetic disorder characterized by sensorineural hearing loss or deafness and progressive vision loss due to retinitis pigmentosa. Sensorineural hearing means it is caused by abnormalities of the inner ear. Retinitis pigmentosa is an eye disease that affects the layer of light-sensitive tissue at the back of the eye (the retina). Vision loss occurs as the light-sensing cells of the retina gradually deteriorate. Night vision loss begins first, followed by blind spots that develop in the side (peripheral) vision, that can enlarge and merge to produce tunnel vision (loss of all peripheral vision). In some cases, vision is further impaired by clouding of the lens of the eye (cataracts).

Epidemiology

Usher syndrome affects approximately 4 to 17 per 100,000 people,1,2 and accounts for about 50 percent of all hereditary deaf-blindness cases.3 The condition is thought to account for 3 to 6 percent of all children who are deaf, and another 3 to 6 percent of children who are hard-of-hearing.

Cause

So far, researchers have found nine genes that cause Usher syndrome. Type 1 Usher syndrome: MY07A, USH1C, CDH23, PCHD15, USH1G

Inheritance

Autosomal recessive inheritance, a 25% chance

Usher syndrome is inherited, which means that it is passed from parents to a child through genes. Each person inherits two copies of a gene, one from each parent. Sometimes genes are altered, or mutated. Mutated genes may cause cells to develop or act abnormally.

Usher syndrome is inherited as an autosomal recessive disorder. “Autosomal” means that men and women are equally likely to have the disorder and equally likely to pass it on to a child of either sex. “Recessive” means that 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 is a carrier who has a 50 percent chance of passing on the abnormal gene to each child. When two carriers with the same mutated Usher syndrome gene have a child together, each birth

Signs and symptoms

Children with type 1 Usher syndrome have profound hearing loss or deafness at birth and have severe balance problems. Many obtain little or no benefit from hearing aids but may be candidates for a cochlear implant—an electronic device that can provide a sense of sound to people with severe hearing loss or deafness. (For more information, read the NIDCD fact sheet Cochlear Implants.) Parents should consult with their child’s doctor and other hearing health professionals early to determine communication options for their child. Intervention should begin promptly, when the brain is most receptive to learning language, whether spoken or signed.

Balance problems associated with type 1 Usher syndrome delay sitting up without support. Walking rarely occurs prior to 18 months. Vision problems with type 1 Usher syndrome usually begin before age 10, starting with difficulty seeing at night and progressing to severe vision loss over several decades.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Abnormal cochlea morphology
• Abnormal electroretinogram
• Ataxia
• Global developmental delay
• Hemianopia
• Intellectual disability(Mental deficiency)
• Iris hypopigmentation(Light eye color)
• Nyctalopia(Night blindness)
• Scotoma
• Sensorineural hearing impairment
• Vestibular hypofunction
• Visual loss(Loss of vision)

30%-79% of people have these symptoms

• Aplasia/Hypoplasia of the cerebellum(Absent/small cerebellum)
• Cataract(Clouding of the lens of the eye)
• High hypermetropia(Severe farsightedness)
• Schizophrenia

5%-29% of people have these symptoms

• Abnormality of dental enamel(Abnormal tooth enamel)
• Anxiety(Excessive, persistent worry and fear)
• Cerebral cortical atrophy(Decrease in size of the outer layer of the brain due to loss of brain cells)
• Depressivity(Depression)
• Hallucinations(Hallucination)
• Subcortical cerebral atrophy

Diagnosis

Diagnosis of Usher syndrome involves pertinent questions regarding the person’s medical history and testing of hearing, balance, and vision. Early diagnosis is important, as it improves treatment success. An eye care specialist can use dilating drops to examine the retina for signs of RP. Visual field testing measures peripheral vision.

An electroretinogram [e-lec-tro-RET-in-o-gram] measures the electrical response of the eye’s light-sensitive cells in the retina. Optical coherence tomography may be helpful to assess for macular cystic changes.

Videonystagmography [vi-de-o-nigh-stag-MAH-gra-fee] measures involuntary eye movements that could signify a balance problem. Audiology testing determines hearing sensitivity at a range of frequencies.

Genetic testing may help in diagnosing Usher syndrome. So far, researchers have found nine genes that cause Usher syndrome. Genetic testing is available for all of them:

Type 1 Usher syndrome: MY07A, USH1C, CDH23, PCHD15, USH1G

Treatment

In infants: an initial trial of hearing aids to stimulate residual hearing and accustom the infant to auditory stimulation. Cochlear implantation should be considered as young as medically feasible. Sign language and tactile signs (once visual loss occurs) for families who choose non-auditory communication.

Specialized training from educators of the hearing impaired. Vestibular compensation therapy for children with residual balance function and sensory substitution therapy for individuals with complete absence of vestibular function. Standard treatments for retinitis pigmentosa.

NIH genetic and rare disease info

• NIH info on Usher syndrome, type 1

Usher syndrome, type 1 is a rare disease.

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