Genetic Disorder that Causes Deaf Blindness
Usher’s syndrome is a heavily debilitating genetic disorder which is relatively infrequent, but severe. Infants are born with Usher’s syndrome, although the severity of their symptoms depends on the genetic factors which caused the illness in the first place. Vision, hearing, and balance impairment are the main characteristics of the disorder. Presently, there is no cure for the condition, but there is lots of research attempting to identify the faulty genes as well as come up with new forms of therapy. When it comes to the history of Usher’s syndrome, the condition was named after a British eye doctor Charles Usher who dealt with it during the first part of the 20th century. Around 50 years earlier a German scientist names Albercht von Grafe was the first person to describe and study the illness in Berlin. His student, Richard Liebreich, continued the research and discovered that the syndrome was recessive as the symptoms only occurred in siblings or in individuals with a family history of the condition. In addition, in order to diagnose Usher’s medical care professionals administer a battery of tests evaluating the three senses affected by the condition. The eyes are thoroughly checked for both the peripheral vision and retinal functioning. A hearing test determines the loudness of sound and its frequencies which are detectable to a person. In some cases balance problems are determined by examining involuntary eye movements, which in many cases can reveal motor inabilities. It should be noted that with adequate social support, empathy, and unconditional love individuals living with Usher’s syndrome can lead relatively independent but satisfying lives.
Types of Usher’s Syndrome
Individuals who are affected by Usher’s syndrome suffer from severe vision, hearing, and balance inabilities. The hearing problems are primarily associated with inner ear anomalies, whereas the vision issues include many factors. The rod cells are often the first ones to start to degenerate, followed by the cone cells. In addition, the Usher’s syndrome can be divided into three distinct categories. The Type I form is characterized by being born with a complete hearing impairment coupled with a loss of vision before the age of 10. These individuals have movement difficulties as well. Further, it is estimated that worldwide the prevalence of Type I Usher’s syndrome is between 3 and 6 individuals per 100, 000. Type II Usher’s syndrome is less debilitating as the children are born with some hearing abilities, and relatively normal vision. The vision is gradually lost by midlife whereas the balance is mostly intact. Lastly, Type III is manifested via hearing and vision loss during life, and some or no balance problems. The severity of each stage depends on the combination of underlying genes. For instance, it is possible for someone to be affected by Type I Usher’s syndrome and although the person was born deaf they retain their vision for most of their life. On the other hand, an individual who suffers from Type III Usher’s syndrome could have no symptoms early on in life but suffer complete vision and hearing loss by midlife. In addition, Usher’s syndrome is equally likely to affect both sexes. As far as the passing of the faulty genes goes, a parent who has one half of the mutated gene is only a carrier and does not develop any symptoms. With every consecutive child the probability that the infant will also be a carrier gradually lessens. If both parents are carriers there is a 25 percent chance that their child will suffer from Usher’s syndrome, while there is 75 percent that he or she will be a carrier.
Causes of Usher’s Syndrome
As Usher’s syndrome is a genetic disorder it is transferred from parents onto children. Every gene is composed of two copies inherited one from each parent. In case there is a mutation of one or both copies of the gene problems will arise. Usher’s syndrome is an autosomal recessive disorder, meaning that the faulty gene is not carried on the sex chromosomes. Also, the mutated copy of the defective gene has to be passed on from both parents in order for the recipient to develop the disorder. In case a child receives one healthy and one abnormal copy of the gene there will be no symptoms, and that person will be a carrier of the mutated copy. If both parents have one healthy and one abnormal copy there is a 1 in 4 possibility that the offspring will be affected. In addition, as genetic counseling is not yet a widespread element of diagnosing Usher’s syndrome or even identifying it, many individuals, especially those without any hearing, vision, or balance problems, are completely unaware of the fact that they carry faulty genes. Unless Usher’s syndrome runs in the family there is no way to find out whether someone is a carrier. Not surprisingly, there are many organizations which are trying to alter the way Usher’s syndrome patients and its carriers are dealt with.