1. Know Your Family Genes
Genetic hearing loss accounts for 30% to 50% of hearing disorders. Thanks to exciting advances in genetic mapping, research is now able to identify more than seventy genes that lead to deafness. The genes responsible for hearing disorders may be dominant, recessive, or sporadic, making it difficult to pinpoint who may be at risk. Knowledge of your family genes can help define where to search for a genetic hearing disorder. The first tests are costly simply because there are so many genetic abnormalities to investigate. Going after a known familial genetic variation is a time and cost-saving tool. If anyone in your family has experienced a hearing disorder, it may be well worth the effort to submit to genetic testing. The process is known as genetic linking analysis. In the long run, everyone will benefit. Identification of familial gene variations can greatly aid in prevention and treatment.
2. Specific Gene Mutations Contribute to Hearing Disorders
The genes responsible for hearing disorders are classified into groups. Specific grouping helps genetic researchers identify the exact pattern of inheritance. This is where it gets really scientific, but here's the breakdown of genetic grouping: autosomal dominants (both parents have the gene), x-linked recessives (usually carried by males, but may be passed from mother to son), and autosomal recessives (the trait exists but has not manifested). Autosomal recessive is the most likely way that hearing loss is passed from parent to child.
3. Hearing Disorders Occur With or Without Other Syndromes
Seventy percent of people with hearing disorders have no other physical or mental abnormality. Specifically testing for GJB2/GJB6/Connexin 26 gene mutation helps determine whether hearing impairment is part of a syndrome. GJB2/GJB6 abnormalities are not associated with any other condition, negating the need for further testing. Charge syndrome refers to a group of symptoms. It is a genetic cause of hearing disorder; identified as recently as 2004. Testing for the gene mutation CHD7 may confirm the diagnosis. Unfortunately, the gene but it is not detectable in everyone. Diagnosis is often made based on physical exam. Charge syndrome is an example of a sporadic genetic abnormality. There are wide variations in the physical and mental manifestations of charge syndrome, involving abnormalities of the eyes, heart, urinary tract, loss of muscle tone, as well as ear abnormalities. Twenty percent of people with Waardenburg syndrome may have hearing loss. Other characteristics include deafness in one ear, two different colored eyes and wide-set eyes. The characteristics may be so mild that the syndrome is missed. Usher syndrome can cause hearing disorders later in life. If you find yourself having difficulty seeing at night, in addition to progressive loss of hearing, you may want to consider genetic testing. By now you realize that any family history of the same symptoms may indicate you have inherited a causative gene. There are three types of hearing and vision loss associated with Usher syndrome; each responsible for a different genetic location. In children, development may be delayed, but most people have normal intelligence. Usher syndrome is the result of an autosomal recessive gene that is passed from parent to child. Treacher Collins syndrome occurs in approximately one in ten thousand births and is very physically distinctive. The characteristics include conductive hearing loss, small chin, respiratory problems, and wide mouth and ear malformations. Mutations in the TCOF1 gene result in Treacher Collins Syndrome. It follows an autosomal dominant pattern of inheritance.
4. Knowledge Yields the Best Outcomes
Knowledge of whether you or your children are at risk of developing a genetic hearing disorder is the first step toward taking action. The importance of genetic testing lies in determining whether there is an associated syndrome, as described above.
5. The Goal of Testing for Genetic Hearing Loss
The goal is to improve communication and provide quality of life for anyone with a genetic hearing disorder. Knowledge is invaluable when determining specific medical treatments and special needs that serve to improve quality of life. According to a survey, funded by the European Commission in 1999, the majority of parents surveyed indicated they would welcome simply knowing the cause if their child's hearing disorder. Due to medical advances in understanding genetic causes of hearing loss, parental wishes can now come true.
