Associate director, harvard medical school center for hereditary deafness. Hearing loss can be caused by changes in genes or by outside factors like injuries, illness or certain medications, or both. 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. Generally, the younger the person is with a hearing impairment, the more likely it was down to genetic factors, disease or physical abnormality. 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. The genetic forms of hearing loss are diagnosed by otologic, audiologic, and physical examination, family history, ancillary testing e. 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. Sensorineural hearing loss snhl is the most common sensory disorder. Tier i and otoseq testing are indicated for any patient with sensorineural hearing loss of unknown etiology. Staff of this laboratory ascertain families with hearing loss, map and identify the responsible genes and study their function in the auditory system. Agerelated hearing loss also known as presbycusis is a decrease in hearing ability that happens with age. Permanent hearing loss at birth or in early childhood is common and has many genetic and environmental. 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. Genes are passed from parents to children and cause things to run in families.
As such, the number of infants identified with hearing loss is likewise on the rise. Hearing impairment, particularly nonsyndromic hearing loss, affects multiple families across the world. Genetics and hearing loss cs mott childrens hospital. Hearing loss is the most common sensory defect in humans, affecting normal communication in 10 percent of people aged 65 years or older. Although exact data is not available, it is likely that genetics plays an important role in hearing loss in the. Genetics and hearing loss hearing loss association of. Unconventional myosins and the genetics of hearing loss. 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. Even if ones hearing loss is down to old age though genetic factors are still at play here. 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.
This information may allow better treatment and management of the hearing loss, and predict the chances that future children will have hearing loss. Recent progress in developing gene therapy treatments for genetic hearing loss has demonstrated tantalizing proofofprinciple in animal models. These tests identify approximately 80 percent of the genetic causes of hearing loss in children with bilateral snhl. A survey of early hearing detection and intervention programs sarah k. Rudman, left, is the clinical chief resident at the university of miami department of otolaryngologyhead and neck surgery. Genetic mutations in over 100 genes can cause congenital nonsyndromic and syndromic hearing loss. 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. Beside agerelated hearing loss, nihl is the second most frequent form of hearing loss. Genetics evaluation guidelines for the etiologic diagnosis. 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. A guide for patients and families understanding the genetics of deafness this booklet was created by.
Nonsyndromic hearing loss can be classified in several different ways. A carrier is a person who carries one copy of a recessive mutation, but does not have hearing loss. For several genetic subtypes of deafness the locus has been mapped on a defined chromosomal region, yet the gene remains. Several factors including infections, noiseexposure, ototoxic medications or genetic disorders could cause hearing impairment. The gene encoding connexin 26 cx26 is known to be the main cause for most recessive gene hearing loss. It can begin as early as a persons thirties or forties and worsens gradually over time. Herein, we describe stateoftheart research on genetic hearing loss treatment through gene therapy and discuss the obstacles to overcome in curative treatments. 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.
Hearing loss can occur because of damage to the ear, especially the inner ear. A specific etiology can be identified in close to 90% of the cases. Hereditary deafness is one of the most genetically heterogeneous conditions known to date. Pdf on feb 10, 2008, ella shalit and others published genetics of hearing loss find, read and cite all the research you need on. It is estimated that the causes of agerelated hearing loss are 3555% genetic.
In most cases, hearing loss is a multifactorial disorder cau. Gene therapy for hearing loss human molecular genetics. There are also a number of things in the environment that can cause hearing loss. In contrast, syndromic hearing loss occurs with signs and symptoms affecting other parts of the body. Their genes make them more predisposed to hearing loss due to ageing or induced by noise, drugs or infections. Clinical aspects of hereditary hearing loss genetics in.
While successful translation of this progress into treatments for humans awaits, there is growing interest from patients, scientists. The genetics of hearing loss can be complicated and difficult to understand. Genetic hearing loss may be linked to health or learning problems. Quite often parents are carriers of a genetic disorder and yet do not display that disorder themselves. Deafness and hereditary hearing loss, nonsyndromic breda. A guide for patients and families harvard university. About 1 in 500 infants is born with or develops hearing loss. For many children with hearing loss, the cause is unknown. 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. For patients and families genetic testing for hearing loss. A child born with hearing loss of a genetic nature can have parents with normal hearing.
The majority of children with genetic hearing loss do not have any other birth defects or major health concerns associated with their 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. To learn more about genetic causes of hearing loss, you may download. Pdf instructions for taking a pedigree author notes.
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. 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. The major impetus behind infant screening has been the improved outcome of speech and language potential in children. Genetic factors make some people more susceptible to hearing loss than others. Hearing loss can also become apparent later in life, referred to as lateonset 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. Most cases of hearing loss detected by newborn screening have a genetic 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. This overview focuses on the clinical features and molecular genetics of common syndromic and nonsyndromic types of hereditary hearing loss. Friedman is the chief of the laboratory of molecular genetics, national institute on deafness and other communication disorders, national institutes of health. Tier i testing includes analysis for mutations in gjb2, gjb6, 12s rrna and trnaser ucn. Understanding the genetics of deafness projects at harvard.
Molecular genetic testing, possible for many types of syndromic and nonsyndromic deafness. 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. Agerelated hearing loss genetics home reference nih. It is a complex condition that is influenced by both environmental factors and genetic factors. Gene therapy, or the treatment of human disease using genetic material, for inner ear dysfunction is coming of age. 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. Genetic hearing loss hereditary hearing loss causes. Genetics and hearing loss perspectives on hearing and. Molecular genetic testing, possible for many types of. Inherited genetic defects play an important role in congenital hearing loss, contributing to about 60% of deafness occurring in infants. Potential treatments for genetic hearing loss in humans nature. Nonsyndromic hearing loss genetics home reference nih. Introduction hearing loss hl is the most common sensory defect in human beings, affecting 1.
Genetic determinants of nonsyndromic hearing impairment. In males, hearing loss is prelingual and rang e from sever e to prof ound while in females hearing loss is. Lateonset hearing loss can be the result of noise exposure. Hearing loss genetic centers in michigan childrens hospital of michigan dmc detroit medical center genetic and metabolic disorders 38329330 c. It has been estimated that at least 1% of human genes may be involved in the pathogenesis of some form of hereditary hearing loss. Many parents are unfamiliar with how hearing loss could be caused by genetic factors. Does my patient have a genetic form of hearing loss. Hearing loss identified by newborn screening can prompt an early investigation into the etiology of the loss. Home test catalog by test az hearing loss panel hearing loss panel forms and documents. For more than half of all deaf and hard of hearing children. Nonsyndromic hearing loss is a partial or total loss of hearing that is not associated with other signs and symptoms. The study of the genetics of hearing loss in humans is fraught with difficulties, mostly due to the shortage of large affected families and heterogeneity of genetic nshl in humans.