Clinical evaluation and etiologic diagnosis of hearing loss: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG)

Hearing loss is a common and complex condition that can occur at any age, can be inherited or acquired, and is associated with a remarkably wide array of etiologies. The diverse causes of hearing loss, combined with the highly variable and often overlapping presentations of different forms of hearing loss, challenge the ability of traditional clinical evaluations to arrive at an etiologic diagnosis for many deaf and hard-of-hearing individuals. However, identifying the etiology of hearing loss may affect clinical management, improve prognostic accuracy, and refine genetic counseling and assessment of the likelihood of recurrence for relatives of deaf and hard-of-hearing individuals. Linguistic and cultural identities associated with being deaf or hard-of-hearing can complicate access to and the effectiveness of clinical care. These concerns can be minimized when genetic and other health care services are provided in a linguistically and culturally sensitive manner. This clinical practice resource offers information about the frequency, causes, and presentations of hearing loss and suggests approaches to the clinical and genetic evaluation of deaf and hard-of-hearing individuals aimed at identifying an etiologic diagnosis and providing informative and effective patient education and genetic counseling.     

A proposal for comprehensive newborn hearing screening to improve identification of deaf and hard-of-hearing children

Early intervention for newborns who are deaf or hard-of-hearing leads to improved language, communication, and social–emotional outcomes. Universal physiologic newborn hearing screening has been widely implemented across the United States with the goal of identifying newborns who are deaf or hard-of-hearing, thereby reducing time to diagnosis and intervention. The current physiologic newborn hearing screen is generally successful in accomplishing its goals but improvements could be made. In the past ten years, genetic testing has emerged as the most important etiological diagnostic test for evaluation of children with deafness and congenital cytomegalovirus has been recognized as a major cause of childhood deafness that may be treatable. A comprehensive newborn hearing screen that includes physiologic, genetic, and cytomegalovirus testing would have multiple benefits, including (1) identifying newborns with deafness missed by the current physiologic screen, (2) providing etiologic information, and (3) possibly decreasing the number of children lost to follow up. We present a framework for integrating limited genetic testing and cytomegalovirus screening into the current physiologic newborn hearing screening. We identify needed areas of research and include an overview of genome sequencing, which we believe will become available over the next decade as a complement to universal physiologic newborn hearing screening.     

Study of the etiology of deafness in an institutionalized population in colombia

To identify causative factors we screened 1,715 deaf individuals from 16 schools for the deaf in Colombia. We found evidence of environmental causation in 579 (33.8%) cases, genetic in 608 (35.4%), and in 528 (30.8%) we were unable to identify the etiology. The degree of hearing loss was severe to profound in 1,238 (72.2%), although in 987 (57.5%) of the deaf population studied the hearing impairment was not noticed until 2 to 5 years of age. The frequent association of deafness with other anomalies underscores the importance of a careful clinical and ophthalmologic evaluation in individuals with hearing loss. Our observations also emphasize the need for programs directed towards the prevention of hearing loss, including primary prevention as well as early diagnosis, investigation of possible genetic causes, and rehabilitation of deaf individuals.     

Study of the etiology of deafness in an institutionalized population in Colombia.

To identify causative factors we screened 1,715 deaf individuals from 16 schools for the deaf in Colombia. We found evidence of environmental causation in 579 (33.8%) cases, genetic in 608 (35.4%), and in 528 (30.8%) we were unable to identify the etiology. The degree of hearing loss was severe to profound in 1,238 (72.2%), although in 987 (57.5%) of the deaf population studied the hearing impairment was not noticed until 2 to 5 years of age. The frequent association of deafness with other anomalies underscores the importance of a careful clinical and ophthalmologic evaluation in individuals with hearing loss. Our observations also emphasize the need for programs directed towards the prevention of hearing loss, including primary prevention as well as early diagnosis, investigation of possible genetic causes, and rehabilitation of deaf individuals.     

Performance of cochlear implant recipients with GJB2-related deafness

Congenital profound hearing loss affects 0.05-0.1% of children and has many causes, some of which are associated with cognitive delay. For prelingually-deafened cochlear implant recipients, the etiology of deafness is usually unknown. Mutations in GJB2 have been established as the most common cause of heritable deafness in the United States. In this report, we identify cochlear implant recipients with GJB2-related deafness and examine the performance of these individuals. Cochlear implant recipients received a battery of perceptive, cognitive, and reading tests. Neither subjects nor examiners knew the etiology of deafness in these individuals. The implant recipients were then examined for mutations in GJB2 using an allele-specific polymerase chain reaction assay, single-strand conformation polymorphism analysis, and direct sequencing. GJB2 mutations were the leading cause of congenital deafness among the cochlear implant recipients screened. Cochlear implant recipients with GJB2-related deafness read within one standard deviation of hearing controls better than other congenitally deaf cochlear implant recipients and non-cochlear implant recipients. Individuals with congenital deafness should be offered GJB2 screening. Positive results establish an etiologic diagnosis and provide prognostic, genetic, and therapeutic information. Effective rehabilitation for profoundly deaf individuals with GJB2-related deafness is possible through cochlear implantation.     

Evaluation of newborn screening bloodspot-based genetic testing as second tier screen for bedside newborn hearing screening

PurposeBedside newborn hearing screening is highly successful in identifying deaf or hard-of-hearing infants. However, newborn hearing screening protocols have high loss to follow-up rates. We propose that bloodspot-based genetic testing for GJB2 alleles can provide a means for rapid confirmation in a subset of infants who fail bedside newborn hearing screening.MethodsWe performed a case-control study comparing the prevalence of common GJB2 mutations from deidentified bloodspots designated as “refer” by newborn hearing screening and contemporaneously selected randomly chosen controls designated as “pass.” Between March 2006 and December 2007, 2354 spots were analyzed for common alleles, c.35delG, c.167delT, c.235delC, and p.V37I in GJB2 with a subset reanalyzed by conventional Sanger sequencing to search for additional alleles.ResultsThe prevalence of biallelic GJB2 mutations in bloodspots from infants who referred by newborn hearing screening is approximately 1 in 50 (23/1177). In contrast, one bloodspot from an infant who passed newborn hearing screening was identified to harbor biallelic GJB2 mutations.ConclusionsThese findings show that when a newborn refers by newborn hearing screening, there is a significant chance that GJB2-related hearing loss is present. Bloodspot-based genetic testing for common GJB2 alleles should be considered as second tier testing for bedside newborn hearing screening.     

Attitudes of deaf individuals towards genetic testing

Recent advances have made molecular genetic testing for several forms of deafness more widely available. Previous studies have examined the attitudes of the deaf towards genetic testing, including prenatal diagnosis. This study examines the attitudes of deaf college students towards universal newborn hearing screening, including molecular testing for specific forms of deafness, as well as the utilization of genetic test results for mate selection. We found that there may be differences in the attitudes of deaf individuals who associate closely with the deaf community (DC), and those who have equal involvement with both the deaf and hearing communities (EIC). The majority perceived newborn hearing screening for deafness to be helpful. However, more members of the EIC than the DC groups support newborn testing for genes for deafness. While there was reported interest in using genetic testing for partner selection, most participants reported they would not be interested in selecting a partner to have children with a specific hearing status. The results of this study point out important differences that genetic professionals should be aware of when counseling deaf individuals.     

Performance of cochlear implant recipients with GJB2‐related deafness

Congenital profound hearing loss affects 0.05–0.1% of children and has many causes, some of which are associated with cognitive delay. For prelingually‐deafened cochlear implant recipients, the etiology of deafness is usually unknown. Mutations in GJB2 have been established as the most common cause of heritable deafness in the United States. In this report, we identify cochlear implant recipients with GJB2‐related deafness and examine the performance of these individuals. Cochlear implant recipients received a battery of perceptive, cognitive, and reading tests. Neither subjects nor examiners knew the etiology of deafness in these individuals. The implant recipients were then examined for mutations in GJB2 using an allele‐specific polymerase chain reaction assay, single‐strand conformation polymorphism analysis, and direct sequencing. GJB2 mutations were the leading cause of congenital deafness among the cochlear implant recipients screened. Cochlear implant recipients with GJB2‐related deafness read within one standard deviation of hearing controls better than other congenitally deaf cochlear implant recipients and non‐cochlear implant recipients. Individuals with congenital deafness should be offered GJB2 screening. Positive results establish an etiologic diagnosis and provide prognostic, genetic, and therapeutic information. Effective rehabilitation for profoundly deaf individuals with GJB2‐related deafness is possible through cochlear implantation. © 2002 Wiley‐Liss, Inc.     

Innovative approach to genetic counseling services for the deaf population

Genetic service providers have stressed the importance of genetic counseling that is nondirective and specific to the personal needs of consultands. Successful genetic counseling for deaf persons often requires special provisions for complex family histories, syndromic conditions, and diversity in communication methods and cultural orientation. The Gallaudet University Genetic Services Center (GSC) was established in 1984 to provide genetic education and counseling services to the deaf community. The GSC staff developed and implemented a standardized system of data collection (family and medical history), clinical evaluation by consultant clinical geneticists, and counseling in sign language. In addition to clinical services, an in-depth educational program for professionals and consumers was developed and carried out. During a 6-year period, over 220 educational presentations were made and 659 deaf persons were seen for genetic evaluation and counseling. Most of these persons were self-referred. Sign language was the preferred means of communication of more than 90% of these individuals. A genetic cause of deafness was diagnosed in over 50% of the deaf consultands and was confirmed by segregation analysis, which had results similar to those reported for other studies of students in schools for the deaf. Special materials and strategies were developed in order to provide genetic services that were sensitive to the cultural and linguistic differences of the deaf population. These included written and visual materials that contained culturally neutral terminology and training of all staff members in sign language and the culture of the deaf. © Wiley-Liss, Inc.     

Frequency of Usher syndrome in two pediatric populations: Implications for genetic screening of deaf and hard of hearing children

PurposeUsher syndrome is a major cause of genetic deafness and blindness. The hearing loss is usually congenital and the retinitis pigmentosa is progressive and first noticed in early childhood to the middle teenage years. Its frequency may be underestimated. Newly developed molecular technologies can detect the underlying gene mutation of this disorder early in life providing estimation of its prevalence in at risk pediatric populations and laying a foundation for its incorporation as an adjunct to newborn hearing screening programs.MethodsA total of 133 children from two deaf and hard of hearing pediatric populations were genotyped first for GJB2/6 and, if negative, then for Usher syndrome. Children were scored as positive if the test revealed ≥1 pathogenic mutations in any Usher gene.ResultsFifteen children carried pathogenic mutations in one of the Usher genes; the number of deaf and hard of hearing children carrying Usher syndrome mutations was 15/133 (11.3%). The population prevalence was estimated to be 1/6000.ConclusionUsher syndrome is more prevalent than has been reported before the genome project era. Early diagnosis of Usher syndrome has important positive implications for childhood safety, educational planning, genetic counseling, and treatment. The results demonstrate that DNA testing for Usher syndrome is feasible and may be a useful addition to newborn hearing screening programs.     

A focus group study of consumer attitudes toward genetic testing and newborn screening for deafness.

PURPOSE: Progress in identifying genes for deafness together with implementation of universal audiologic screening of newborns has provided the opportunity for more widespread use of molecular tests to detect genetic forms of hearing loss. Efforts to assess consumer attitudes toward these advances have lagged behind. METHODS: Consumer focus groups were held to explore attitudes toward genetic advances and technologies for hearing loss, views about newborn hearing screening, and reactions to the idea of adding molecular screening for hearing loss at birth. Focus group discussions were recorded, transcribed and analyzed. RESULTS: Five focus groups with 44 participants including hearing parents of deaf children, deaf parents and young deaf adults were held. Focus group participants supported the use of genetic tests to identify the etiology of hearing loss but were concerned that genetic information might influence reproductive decisions. Molecular newborn screening was advocated by some; however, others expressed concern about its effectiveness. CONCLUSION: Documenting the attitudes of parents and other consumers toward genetic technologies establishes the framework for discussions on the appropriateness of molecular newborn screening for hearing loss and informs specialists about potential areas of public education necessary prior to the implementation of such screening.     

Innovative approach to genetic counseling services for the deaf population.

Genetic service providers have stressed the importance of genetic counseling that is nondirective and specific to the personal needs of consultants. Successful genetic counseling for deaf persons often requires special provisions for complex family histories, syndromic conditions, and diversity in communication methods and cultural orientation. The Gallaudet University Genetic Services Center (GSC) was established in 1984 to provide genetic education and counseling services to the deaf community. The GSC staff developed and implemented a standardized system of data collection (family and medical history), clinical evaluation by consultant clinical geneticists, and counseling in sign language. In addition to clinical services, an in-depth educational program for professionals and consumers was developed and carried out. During a 6-year period, over 220 educational presentations were made and 659 deaf persons were seen for genetic evaluation and counseling. Most of these persons were self-referred. Sign language was the preferred means of communication of more than 90% of these individuals. A genetic cause of deafness was diagnosed in over 50% of the deaf consultants and was confirmed by segregation analysis, which had results similar to those reported for other studies of students in schools for the deaf. Special materials and strategies were developed in order to provide genetic services that were sensitive to the cultural and linguistic differences of the deaf population. These included written and visual materials that contained culturally neutral terminology and training of all staff members in sign language and the culture of the deaf.     

Aetiology of childhood hearing loss in Cameroon (sub-Saharan Africa)

BackgroundSevere hearing loss is a global problem affecting particularly developing countries. There is scarcity of recent published data on the epidemiology of childhood deafness in sub-Saharan Africa.ObjectiveTo determine the etiological profile of severe childhood deafness in Cameroon.MethodsProspective cross-sectional study of patients with a severe hearing loss that started before the age of 15 years. Detailed family and medical history was obtained; careful clinical, otological and audiological examinations were performed.ResultsA total of 582 patients with a severe hearing loss were examined. Prelingual deafness accounted for 75.1% (n = 437), with a mean age at medical diagnosis of 3.3 ± 1.2 years. This late presentation may be explained by limited parental awareness of signs raising suspicion of hearing loss, poor access to health care and the absence of neonatal screening for hearing loss in Cameroon. Identified genetic causes accounted for 14.8% (n = 86), putative environmental causes for 52.6% (n = 306) and unknown causes for 32.6% (n = 190). Amongst Genetic causes, the syndromic hearing loss accounted for 13.1% (n = 12) of cases, the rest being non syndromic (n = 74). Consanguineous families accounted for 5.7% (n = 33) of the whole sample, and 15.1% (n = 13) of genetic cases. No union between deaf parents was observed.ConclusionThese data highlight the possible predominance of putative environmental causes of childhood deafness in Cameroon, and emphasize the need for improved policies for prevention of infectious diseases and for neonatal hearing screening. However, further molecular analyses and targeted CT scan investigations are required to more accurately gauge the contribution of genetics etiologies.     

Fitness Among Individuals with Early Childhood Deafness: Studies in Alumni Families from Gallaudet University

The genetic fitness of an individual is influenced by their phenotype, genotype and family and social structure of the population in which they live. It is likely that the fitness of deaf individuals was quite low in the Western European population during the Middle Ages. The establishment of residential schools for deaf individuals nearly 400 years ago resulted in relaxed genetic selection against deaf individuals which contributed to the improved fitness of deaf individuals in recent times. As part of a study of deaf probands from Gallaudet University, we collected pedigree data, including the mating type and the number and hearing status of the children of 686 deaf adults and 602 of their hearing siblings. Most of these individuals had an onset of severe to profound hearing loss by early childhood. Marital rates of deaf adults were similar to their hearing siblings (0.83 vs. 0.85). Among married individuals, the fertility of deaf individuals is lower than their hearing siblings (2.06 vs. 2.26, p = 0.005). The fitness of deaf individuals was reduced (p = 0.002). Analysis of fertility rates after stratification by mating type reveals that matings between two deaf individuals produced more children (2.11) than matings of a deaf and hearing individual (1.85), suggesting that fertility among deaf individuals is influenced by multiple factors.     

Assessing parental attitudes toward genetic testing for childhood hearing loss: before and after genetic consultation

We report on the development of a Genetic Attitude Assessment Tool (GAAT) to measure parental attitudes in contemplating genetic testing for childhood hearing loss, and to examine the differences in assessments made before and after genetic counseling. The GAAT tool was administered to a convenient sample of 119 parents of children with bilateral sensorineural hearing loss. The respondents completed the survey either before (n = 77) or after (n = 42) genetic counseling. Exploratory Factor Analysis was applied to identify and quantify the underlying psychosocial structure. Our results showed the validated 54-item GAAT instrument contains six subscales: (1) "test intention," (2) "beliefs in non-genetic causes of hearing loss," (3) "deferral of decision to undergo genetic testing," (4) "appropriate use of genetic testing results," (5) "beliefs in the benefits," and (6) "concerns about stigma." The respondents who answered the survey after genetic counseling had higher "test intention" (P = 0.017) and endorsed to a greater extent "beliefs in the benefits" (P < 0.001). They believed to a lesser extent that childhood hearing loss was due to "non-genetic causes" (P < 0.001) and were less inclined to prefer "decision deferral" (P = 0.031). Respondents who themselves had a hearing loss expressed a significantly weaker belief in "non-genetic causes" of hearing loss (P < 0.0001). In conclusion the validated GAAT instrument is responsive to changes in parental attitudes after genetic counseling. The GAAT may be used to monitor parental attitudes serially, to further understand how parental attitudes change from pre genetic counseling, post genetic counseling, to post test result disclosure.     

The peroxisomal disorder spectrum and Heimler syndrome: Deep phenotyping and review of the literature

The spectrum of peroxisomal disorders is wide and comprises individuals that die in the first year of life, as well as people with sensorineural hearing loss, retinal dystrophy and amelogenesis imperfecta. In this article, we describe three patients; two diagnosed with Heimler syndrome and a third one with a mild‐intermediate phenotype. We arrived at these diagnoses by conducting complete ophthalmic (National Eye Institute), auditory (National Institute of Deafness and Other Communication Disorders), and dental (National Institute of Dental and Craniofacial Research) evaluations, as well as laboratory and genetic testing. Retinal degeneration with macular cystic changes, amelogenesis imperfecta, and sensorineural hearing loss were features shared by the three patients. Patients A and C had pathogenic variants in PEX1 and Patient B, in PEX6. Besides analyzing these cases, we review the literature regarding mild peroxisomal disorders, their pathophysiology, genetics, differential diagnosis, diagnostic methods, and management. We suggest that peroxisomal disorders are considered in every child with sensorineural hearing loss and retinal degeneration. These patients should have a dental evaluation to rule out amelogenesis imperfecta as well as audiologic examination and laboratory testing including peroxisomal biomarkers and genetic testing. Appropriate diagnosis can lead to better genetic counseling and management of the associated comorbidities.     

Hearing impairment as an early sign of alpha‐mannosidosis in children with a mild phenotype: Report of seven new cases

Alpha‐mannosidosis (AM) is a very rare (prevalence: 1/500000 births) autosomal recessive lysosomal storage disorder. It is characterized by multi‐systemic involvement associated with progressive intellectual disability, hearing loss, skeletal anomalies, and coarse facial features. The spectrum is wide, from very severe and lethal to a milder phenotype that usually progresses slowly. AM is caused by a deficiency of lysosomal alpha‐mannosidase. A diagnosis can be established by measuring the activity of lysosomal alpha‐mannosidase in leucocytes and screening for abnormal urinary excretion of mannose‐rich oligosaccharides. Genetic confirmation is obtained with the identification of MAN2B1 mutations. Enzyme replacement therapy (LAMZEDE^R) was approved for use in Europe in August 2018. Here, we describe seven individuals from four families, diagnosed at 3–23 years of age, and who were referred to a clinical geneticist for etiologic exploration of syndromic hearing loss, associated with moderate learning disabilities. Exome sequencing had been used to establish the molecular diagnosis in five cases, including a two‐sibling pair. In the remaining two patients, the diagnosis was obtained with screening of urinary oligosaccharides excretion and the association of deafness and hypotonia. These observations emphasize that the clinical diagnosis of AM can be challenging, and that it is likely an underdiagnosed rare cause of syndromic hearing loss. Exome sequencing can contribute significantly to the early diagnosis of these nonspecific mild phenotypes, with advantages for treatment and management.     

遗传性非综合征型耳聋的临床实践指南

遗传因素是非综合征型聋常见的致病原因。随着分子检测技术的发展和日臻成熟,基因诊断和遗传咨询越来越多地影响着耳聋的临床实践。新生儿听力筛查的普及有助于耳聋的早期发现,耳聋基因筛査和诊断的普及有助于明确其病因,临床基因诊断和遗传咨询则有助于耳聋的早期干预。至今发现的非综合征型聋的致病基因有110个,鉴定其致病基因在临床上仍存在很多挑战。临床遗传咨询和产前诊断的开展,对耳聋基因检测和数据解读提出了更高的要求。本指南阐述了非综合征型耳聋的人群发病率、致病基因谱、遗传方式、疾病发展过程、临床表现、基因型-表型对应关系、基因诊断、治疗和干预,以及耳聋预防和再发风险评估等关键问题,为遗传咨询师、临床耳科医师及基因检测专业人员提供指导。