Usher Syndrome

Usher syndrome is a rare, inherited condition or disorder characterized by total or partial loss of hearing and vision that worsen over time. The loss of hearing is often described as sensorineural, which implies that results from the inner ear’s abnormalities (Williams, 2008). The vision loss is caused by an eye illness referred to as retinitis pigmentosa (RP), which affects the light-sensitive tissue’s layer at the retina (Williams, 2008). According to the National Institutes of Health's recent report, 3 to 6 percent of children with deafness and 3 to 6 percent of children with hearing difficulties have Usher syndrome (Rogan, 2010). This paper explores usher syndrome, with the focus on its meaning, types, causes, diagnosis, treatment, and prognosis.

Meaning of Usher Syndrome

            Usher syndrome is a rare inherited or genetic disorder, characterized by loss of hearing and vision, and named after Charles Usher, the Scottish ophthalmologist who examined the condition’s transmission and pathology in 1914 (Ahmed et al., 2003).  The condition is presently incurable and stands as the leading cause of deafness and blindness. Children with Usher syndrome often born with hearing difficulties or deafness, while the loss of vision usually develops during childhood or adolescence (Ahmed et al., 2003). Nevertheless, most people with RP maintain some central vision throughout their lifetime. Scientists have identified three Usher syndrome types based on the degree of vision and hearing loss, the age of vision loss occurrence, and the presence of balance problems (Rogan, 2010).

Types of Usher Syndrome

            Scientists have categorized Usher syndrome into type 1, type 2, and type 3 Usher syndrome, with type 1 and type 2 being the most common in the United States, accounting for about 95 percent of all Usher syndrome cases in the United States (Ouyang et al., 2005).

Type 1 (Usher Syndrome I)

            Babies born with type 1 Usher syndrome are almost totally deaf at the time of birth, and they have severe balance problems. They also develop vision problems in early childhood and progress rapidly to total blindness. Besides, children with type 1 Usher syndrome are late walkers, and they often have less likelihood of benefitting from hearing aids (Ouyang et al., 2005).

Type 2 (Usher Syndrome II)

            Children born with Usher syndrome II have moderate to severe loss of hearing at birth. They usually develop night vision problems at teenage, and they often experience a slow progress in vision impairment, which does not lead to total blindness. Besides, children born with type 2 Usher syndrome have normal balance and can benefit from various hearing aids (Reiners et al., 2006).

Type 3 (Usher Syndrome III)

            Children born with type 3 Usher syndrome usually have normal hearing at the time of birth and almost normal balance.  The hearing and vision losses are often gradual, and the affected children can benefit from various forms of hearing aids. Night blindness usually starts during puberty, while total blindness begins by middle age (Ouyang et al., 2005).

Causes of Usher Syndrome

            Usher syndrome is an inherited or genetic disorder, which implies that it is passed from parents to children and results from gene mutations. Usher syndrome is described as an autosomal recessive disorder, which means that it can affect both males and females (Williams, 2008). A child can get either a normal or mutated gene from each parent, and a child who receives a mutated gene from either parent will develop or have the Usher syndrome. The probability that a child whose both parents have Usher genes will have Usher syndrome is 25 percent (Rogan, 2010).

The Cause of Vision Loss

            The eye component that is responsible for vision is the retina, located at the back of the eye. The gene mutation that causes Usher syndrome often affects the light-sensing cells of the retina, called cones and rods, resulting in a condition termed as retinitis pigmentosa (RP). The RP condition leads to the gradual deterioration of the retina’s light-sensing cones and rods from the outer edges. As the RP condition worsens, an individual begins to lose peripheral vision, which then advances to loss of central vision (Williams, 2008).

The Cause of Hearing Loss

            The hearing loss in Usher syndrome results from the gene mutations that affect the cochlea’s nerve cells by interfering with their normal sound transmission. The cochlea is the ear component that is responsible for sound transmission (Rogan, 2010).

Diagnosis and Testing for Usher Syndrome

            The diagnosis of Usher syndrome is based on vision, hearing, and balance tests. Usher gene testing can also confirm the diagnosis, although it is not necessary (Ahmed et al., 2003).

Hearing Testing

            Almost all children born in the United States undergo hearing screening after birth, and those who fail to be screened have to undergo follow-up hearing test to assess them for hearing loss. Depending on additional symptoms and signs, genetic testing may be conducted to determine if they possess an Usher syndrome gene. Teenagers or older children with hearing loss should go through an audiology evaluation to examine the loudness of sound that is suitable for their ears (Reiners et al., 2006).

Vision Testing

            Usher syndrome may remain undiagnosed until the child begins experiencing night blindness, which occurs before age ten in Usher syndrome I and during teenage years in Usher syndrome II. The testing for vision may include physical assessment of the retina aimed at detecting changes in blood vessels, bone spicules, and waxy state of the retina surface (Ouyang et al., 2006). Visual testing may also include visual field testing, which involves measuring of the peripheral vision. Electroretinogram (ERG) examination may also be conducted to confirm the RP’s diagnosis, as well as the retina’s response to light (Ouyang et al., 2006).  

Balance Testing

            Balance testing is usually performed using an Electronystagmogram (ENG), which examines involuntary eye movements, thereby aiding in the detection of balance problems (Ahmed et al., 2003). 

Treatment and Management of Usher Syndrome

            Despite the several studies that have been conducted on Usher syndrome, its cure has not been found, and various Usher syndrome treatments focus on assisting the affected children to adapt to vision and hearing losses to enable them to enjoy normal lives as much as possible. The various treatments for Usher syndrome include hearing aids, cochlear implants, braille instruction, auditory training, and low-vision services (Williams, 2008). Others include orientation and mobility training, as well as the use of various assistive listening devices, such as microphones, headsets, special phones, and other sound-amplifying devices. Additionally, according to the Foundation for Fighting Blindness, high Vitamin A doses can reduce various eye responses to RP. Parents should, therefore, seek vision specialists' advice before giving their children vitamin A (Williams, 2008).

Prognosis for Usher Syndrome

            Although Usher syndrome has no cure, children with Usher syndrome can still live happy and complete lives with the assistance of various training and educational programs that meet their needs. Usher syndrome's early diagnosis is essential since it enables children with Usher syndrome to receive special assistance earlier enough, thereby equipping them with the necessary skills for managing their hearing and vision loss (Reiners et al., 2006; Rogan, 2010).

Conclusion

            Under syndrome is a rare genetic condition or disorder, characterized by loss of hearing and vision, which often occurs during childhood or adolescence. Usher syndrome exists in three different types, with each type having unique symptoms. It is advisable for parents whose children have Usher syndrome to visit their vision and hearing specialists as early as possible.  That is because the earlier such children begin working with vision and hearing specialists, the easier they can learn to manage hearing and vision loss through speaking and communicating with sign language.

References

Ahmed, Z., Riazuddin, S., Riazuddin, S., & Wilcox, E. (2003). The molecular genetics of Usher syndrome. Clinical Genetics, 63(6), 431-444. doi: 10.1034/j.1399-0004.2003.00109.x

Ouyang, X., Yan, D., Du, L., Hejtmancik, J., Jacobson, S., & Nance, W. et al. (2005). Characterization of Usher syndrome type I gene mutations in an Usher syndrome patient population. Human Genetics, 116(4), 292-299. doi: 10.1007/s00439-004-1227-2

Reiners, J., Nagel-Wolfrum, K., Jürgens, K., Märker, T., & Wolfrum, U. (2006). Molecular basis of human Usher syndrome: Deciphering the meshes of the Usher protein network provides insights into the pathomechanisms of the Usher disease. Experimental Eye Research, 83(1), 97-119. doi: 10.1016/j.exer.2005.11.010

Rogan, P. (2010). Usher Syndrome Splicing Variants Evaluated in Nasal Epithelial Cells. Human Mutation, 31(6), v-v. doi: 10.1002/humu.21291

Williams, D. (2008). Usher syndrome: Animal models, retinal function of Usher proteins, and prospects for gene therapy. Vision Research, 48(3), 433-441. doi: 10.1016/j.visres.2007.08.015