Nonsyndromic hearing loss is a partial or total loss of hearing that is not associated with other signs and symptoms. Bronya keats, is professor and chair of the department of genetics and director of the molecular and human genetics center at louisiana state university health sciences center. Beside agerelated hearing loss, nihl is the second most frequent form of hearing loss. In the case of hearing loss, variations in a large number of different genes can lead to hearing loss by altering the ability of the inner ear to function properly. For patients and families genetic testing for hearing loss. Generally, the younger the person is with a hearing impairment, the more likely it was down to genetic factors, disease or physical abnormality.
A genetics evaluation can provide the family and providers with several critical pieces of information. Although exact data is not available, it is likely that genetics plays an important role in hearing loss in the. A genetic hearing loss may be inherited in an autosomal dominant, autosomal recessive, or xlinked mendelian manner, or through the maternal lineage by mitochondrial inheritance. Hearing impairment, particularly nonsyndromic hearing loss, affects multiple families across the world. Friedman is the chief of the laboratory of molecular genetics, national institute on deafness and other communication disorders, national institutes of health. Hearing loss is the most common sensory defect in humans, affecting normal communication in 10 percent of people aged 65 years or older. Home test catalog by test az hearing loss panel hearing loss panel forms and documents. Rudman, left, is the clinical chief resident at the university of miami department of otolaryngologyhead and neck surgery. Genetic determinants of nonsyndromic hearing impairment. It has been estimated that at least 1% of human genes may be involved in the pathogenesis of some form of hereditary hearing loss. For recessive hearing loss, both copies of a gene must be mutated to get hearing loss. Genetics and hearing loss perspectives on hearing and.
Hearing loss identified by newborn screening can prompt an early investigation into the etiology of the loss. Staff of this laboratory ascertain families with hearing loss, map and identify the responsible genes and study their function in the auditory system. The genetics of hearing loss can be complicated and difficult to understand. Recent progress in developing gene therapy treatments for genetic hearing loss has demonstrated tantalizing proofofprinciple in animal models. Genes are passed from parents to children and cause things to run in families. Several factors including infections, noiseexposure, ototoxic medications or genetic disorders could cause hearing impairment. This overview focuses on the clinical features and molecular genetics of common syndromic and nonsyndromic types of hereditary hearing loss. The gene encoding connexin 26 cx26 is known to be the main cause for most recessive gene hearing loss. While successful translation of this progress into treatments for humans awaits, there is growing interest from patients, scientists. Tier i and otoseq testing are indicated for any patient with sensorineural hearing loss of unknown etiology.
More than 400 syndromes have been identified with hearing loss as a symptom mutations in certain genes cause sensitivity to specific antibiotics that, if used causes hearing loss in affected individuals. Even if ones hearing loss is down to old age though genetic factors are still at play here. Gene therapy for hearing loss human molecular genetics. A carrier is a person who carries one copy of a recessive mutation, but does not have hearing loss. Inherited genetic defects play an important role in congenital hearing loss, contributing to about 60% of deafness occurring in infants. A survey of early hearing detection and intervention programs sarah k. The most common forms of genetic hearing loss are due to the dominant and recessive genes of which 15% is from dominant, 70% from recessive, and 15% results from other modes of inheritance. Their genes make them more predisposed to hearing loss due to ageing or induced by noise, drugs or infections.
For many children with hearing loss, the cause is unknown. The main intent of genetic testing for a child who is deaf or hard of hearing is optimal care and management, precision medicine, for that child. Hereditary deafness is one of the most genetically heterogeneous conditions known to date. Genetic hearing loss may be linked to health or learning problems.
Introduction hearing loss hl is the most common sensory defect in human beings, affecting 1. It is estimated that the causes of agerelated hearing loss are 3555% genetic. There are also a number of things in the environment that can cause hearing loss. Genetics of early childhood hearing loss 60% of congenital deafness has a primary genetic etiology a complete genetics evaluation in a young child with a significant hearing loss has a high diagnostic yield. Genetics evaluation guidelines for the etiologic diagnosis. In contrast, syndromic hearing loss occurs with signs and symptoms affecting other parts of the body. When a child is born with hearing loss or develops hearing loss early in childhood, over 50% of the time the cause is genetic and due to a genetic change, or mutation. Deafness and hereditary hearing loss, nonsyndromic breda. Associate director, harvard medical school center for hereditary deafness. About 1 in 500 infants is born with or develops hearing loss. Herein, we describe stateoftheart research on genetic hearing loss treatment through gene therapy and discuss the obstacles to overcome in curative treatments. Agerelated hearing loss genetics home reference nih.
Lateonset hearing loss can be the result of noise exposure. For more than half of all deaf and hard of hearing children. These tests identify approximately 80 percent of the genetic causes of hearing loss in children with bilateral snhl. In males, hearing loss is prelingual and rang e from sever e to prof ound while in females hearing loss is. Molecular genetic testing, possible for many types of. Pdf on feb 10, 2008, ella shalit and others published genetics of hearing loss find, read and cite all the research you need on. Agerelated hearing loss also known as presbycusis is a decrease in hearing ability that happens with age.
The major impetus behind infant screening has been the improved outcome of speech and language potential in children. Hearing loss can also become apparent later in life, referred to as lateonset hearing loss. Genetics and hearing loss cs mott childrens hospital. Functional variants in known hearing impairment genes. Genetic hearing loss hereditary hearing loss causes. Quite often parents are carriers of a genetic disorder and yet do not display that disorder themselves. Genetic mutations in over 100 genes can cause congenital nonsyndromic and syndromic hearing loss. This renders noiseinduced hearing loss nihl one of the most important occupational health hazards.
Sensorineural hearing loss snhl is the most common sensory disorder. Gene therapy, or the treatment of human disease using genetic material, for inner ear dysfunction is coming of age. For several genetic subtypes of deafness the locus has been mapped on a defined chromosomal region, yet the gene remains. Understanding the genetics of deafness projects at harvard. Genetics and hearing loss hearing loss association of. Pdf instructions for taking a pedigree author notes. It can begin as early as a persons thirties or forties and worsens gradually over time. One of the most common birth defects is hearing loss or deafness congenital, which can affect as many as three of every 1,000 babies born.
Genetics of early childhood hearing loss the past decade has seen a continued increase in the utilization of newborn screening for hearing loss. One common way is by the conditions pattern of inheritance. Genes associated with hearing loss are often called hearing loss genes. Its underlying etiologies include a broad spectrum of genetic and environmental factors that can lead to hearing loss that is congenital or late onset, stable or progressive, drug related, noise induced, age related, traumatic or postinfectious. Most cases of hearing loss detected by newborn screening have a genetic etiology. Genetic factors make some people more susceptible to hearing loss than others. Genedx is a world leader in genomics with an acknowledged expertise in rare and ultrarare genetic disorders, as well as an unparalleled comprehensive genetic testing menu.
To learn more about genetic causes of hearing loss, you may download. The genetic forms of hearing loss are diagnosed by otologic, audiologic, and physical examination, family history, ancillary testing e. Permanent hearing loss at birth or in early childhood is common and has many genetic and environmental. As such, the number of infants identified with hearing loss is likewise on the rise. Clinical aspects of hereditary hearing loss genetics in. It is a complex condition that is influenced by both environmental factors and genetic factors. A child born with hearing loss of a genetic nature can have parents with normal hearing. As you work to identify the cause of your childs hearing loss, it will be helpful to have a basic understanding of genetics and the major categories of inheritance. The majority of children with genetic hearing loss do not have any other birth defects or major health concerns associated with their hearing loss. This booklet is designed to help explain the role of genetics in hearing loss, how genetic testing is done, what the results of genetic tests mean, and what options are available for treatment and counseling. Many parents are unfamiliar with how hearing loss could be caused by genetic factors. Hearing loss can be caused by changes in genes or by outside factors like injuries, illness or certain medications, or both. Hearing loss genetic centers in michigan childrens hospital of michigan dmc detroit medical center genetic and metabolic disorders 38329330 c.
The hereditary hearing loss homepage aims to give an uptodate overview of the genetics of hereditary hearing impairment for researchers and clinicians working in the field this site lists data and links for all known gene localizations and identifications for monogenic nonsyndromic hearing impairment. A guide for patients and families understanding the genetics of deafness this booklet was created by. Hearing loss can occur because of damage to the ear, especially the inner ear. Nonsyndromic hearing loss can be classified in several different ways. Overall, the amount of different genetic data presented here variants with earlyonset and lateonset hearing loss in addition to genetic association with normal hearing function, together with relevant functional evidence. Unconventional myosins and the genetics of hearing loss. Does my patient have a genetic form of hearing loss. Tier i testing includes analysis for mutations in gjb2, gjb6, 12s rrna and trnaser ucn. Molecular genetic testing, possible for many types of syndromic and nonsyndromic deafness. Potential treatments for genetic hearing loss in humans nature. Pdf on mar 28, 2012, nejat mahdieh and others published genetics of hearing loss find, read and cite all the research you need on researchgate. This information may allow better treatment and management of the hearing loss, and predict the chances that future children will have hearing loss. A guide for patients and families harvard university.
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