Association of SLC26A4 mutations, morphology, and hearing in pendred syndrome and NSEVA

Variability in Inner Ear Morphology Among a Family With Pendred Syndrome Due to a SLC26A4 Gene Variant

OBJECTIVES

Pendred syndrome, an autosomal recessive disorder, is often associated with pathogenic variants of the SLC26A4 gene that encodes the pendrin protein. Given its autosomal recessive inheritance, tracing the family history and screening siblings become crucial once a diagnosis of Pendred syndrome is confirmed. This case report aims to underscore the variability in inner ear morphology within a family diagnosed with Pendred syndrome, all carrying the same SLC26A4 gene mutation.

METHODS

A chart review and a review of the literature.

RESULTS

We present a family of 4, all of whom possess sensorineural hearing loss due to the same homozygous SLC26A4 variant c.919-2A>G. Intriguingly, clinical manifestations, especially inner ear deformities, displayed variability among family members. Notably, 1 family member exhibited a normal cochleovestibular structure morphology, which was rarely reported in the literature.

CONCLUSIONS

This report highlights the significance of genetic testing and familial consultation when a proband exhibits typical Pendred syndrome symptoms. It also underscores that the inner ear morphology can exhibit variability among family members, even with the same homozygous SLC26A4 variant.

Incomplete partition type II in its various manifestations: isolated, in association with EVA, syndromic, and beyond; a multicentre international study

PURPOSE

Incomplete partition type II (IP-II) is characterized by specific histological features and radiological appearance. It may occur in isolation or in association with an enlarged vestibular aqueduct (EVA). Among those with IP-II and EVA, a subset has a diagnosis of Pendred syndrome. This study aimed to explore the prevalence of isolated IP-II, IP-II with EVA, and cases with a genetic or syndromic basis in our cohort.

METHODS

From a large, multicentre database of dysplastic cochleae (446 patients, 892 temporal bones), those with imaging features of IP-II were examined in detail, including whether there was a genetic or syndromic association.

RESULTS

A total of 78 patients with IP-II were identified. Among these, 55 patients had bilateral IP-II and EVA (only 12 with typical Mondini triad), 8 with bilateral IP-II and normal VA, 2 with bilateral IP-II and unilateral EVA, and 13 with unilateral IP-II (9 with unilateral EVA). Among the group with bilateral IP-II and bilateral EVA in whom genetic analysis was available, 14 out of 29 (48%) had SLC26A4 mutations and a diagnosis of Pendred syndrome, 1 had a FOXI1 mutation, and a few other genetic abnormalities; none had KCNJ10 pathogenic variants.

CONCLUSION

Bilateral IP-II-bilateral EVA may be seen in the context of Pendred syndrome (SLC26A4 or FOXI1 mutations) but, in the majority of our cohort, no genetic abnormalities were found, suggesting the possibility of unknown genetic associations. IP-II in isolation (without EVA) is favored to be genetic when bilateral, although the cause is often unknown.

Causes of hearing loss and implantation age in a cohort of Danish pediatric cochlear implant recipients

INTRODUCTION

Sensorineural hearing loss (SNHL) is the most common birth disorder. The cause of SNHL is heterogeneous and varies in different populations. Understanding the causes of a hearing loss (HL) predict the outcome of cochlear implantation and is of great importance in understanding the mechanism of the disease and in providing the best treatment. Undiagnosed and untreated HL has a profound effect on the acquisition of early communication skills, speech, language, academic, emotional, and psychosocial development in children.

OBJECTIVES

To determine the cause of HL and implantation age in pediatric cochlear implant (CI) users in a Danish population.

METHODS

Data of 100 children (54 females and 46 males), age 0-17 years, was analyzed. All of the children were implanted during 2020-2022.

RESULTS

Hereditary HL was diagnosed in 44 cases (44%), with pathogenic variants in the SLC26A4 gene found in 14 cases (14%). Syndromic HL was diagnosed in 23 children (23%). Non-syndromic HL was diagnosed in 21 children (21%), where the most common genetic variation was found in the GJB2 gene. Acquired prenatal and postnatal sensory disorders TORCH risk factors were associated with HL in 25 cases (25%). Congenital CMV DNA was diagnosed in 23 samples (23%). The cause of the HL remained unknown for 31 (31%) children. In 70 (70%) of the participants the HL was diagnosed at time of newborn hearing screening (NHS). Twenty-three of the children were diagnosed with congenital severe to profound bilateral HL and were simultaneously implanted between 8 and 14 months (mean age 10.5 months). In the remaining 47 cases, the HL was progressive and the children were implanted when the HL reached the criteria for implantation.

CONCLUSIONS

In the current study, the major causes of HL were alterations in the SLC26A4 gene: 13% with Pendred syndrome and 1% non-syndromic. Thirty-one (31%) had HL of unknown origin and almost half of these cases had inner ear malformations (n = 16).

Can MRI biomarkers for hearing loss in enlarged vestibular aqueduct be measured reproducibly?

OBJECTIVE

Morphological features of an enlarged endolymphatic duct (ED) and sac (ES) are imaging biomarkers for genotype and hearing loss phenotype. We determine which biomarkers can be measured in a reproducible manner, facilitating further clinical prediction studies in enlarged vestibular aqueduct hearing loss.

METHODS

A rater reproducibility study. Three consultant radiologists independently measured previously reported MRI ED & ES biomarkers (ED midpoint width, maximal ED diameter closest to the vestibule, ES length, ES width and presence of ES signal heterogeneity) and presence of incomplete partition Type 2 from 80 ears (T₂ weighted axial MRI). Interclass correlation coefficients (ICC) and Gwet's Agreement Coefficients (AC) were generated to give a measure of reproducibility for both continuous and categorical feature measures respectively.

RESULTS

ES length, width and sac signal heterogeneity showed adequate reproducibility (ICC 95% confidence intervals 0.77-0.95, Gwet's AC for sac heterogeneity 0.64). When determining ED midpoint width, measurements from multiple raters are required for "good" reliability (ICC 95% CI 0.75-0.89). Agreement on the presence of incomplete partition Type 2 ranged from "moderate" to "substantial".

CONCLUSIONS

Regarding MR imaging, the opinion of multiple expert raters should be sought when determining the presence of an enlarged ED defined by midpoint width. ED midpoint, ES length, width and signal heterogeneity have adequate reproducibility to be further explored as clinical predictors for audiological phenotype.

ADVANCES IN KNOWLEDGE

We report which ED & ES biomarkers are reproducibly measured. Researchers can confidently utilise these specific biomarkers when modelling progressive hearing loss associated with enlarged vestibular aqueduct.

The effect of SLC26A4 gene mutations on long-term rehabilitative outcomes in cochlear implant patients

BACKGROUND

SLC26A4 gene mutations related to hearing loss patients can obtain good hearing and speech rehabilitation effects after cochlear implantation (CI).

OBJECTIVE

To explore the long-term rehabilitative outcomes of CI in patients with different SLC26A4 mutation groups.

MATERIAL AND METHODS

Clinical data of 71 patients with SLC26A4 gene mutations who received CI in the Second Hospital of Lanzhou University from 2012 to 2015 were retrospectively reviewed. According to the genetic test results, use One-way ANOVA analysis to compare the differences in auditory results, categories of auditory performance (CAP) and speech intelligibility rating (SIR) index questionnaire scores and speech recognition rates among different groups in 4-5 years after CI.

RESULT

Compared with other genotypes of SLC26A4, the patients with homozygous mutation of c.919-2A > G in SLC26A4 had better hearing aid threshold at 500 Hz and better recognition rates of Yangyang words than other monoallelic mutation groups after CI (p < .05).

CONCLUSIONS AND SIGNIFICANCE

The most common hot spot mutation of SLC26A4 gene is c.919-2A > G. The patients with homozygous mutation of c.919-2A > G in SLC26A4 gene had partly better hearing and speech rehabilitation than other monoallelic mutation groups after CI.

The Genetic Background of Hearing Loss in Patients with EVA and Cochlear Malformation

The most frequently observed congenital inner ear malformation is enlarged vestibular aqueduct (EVA). It is often accompanied with incomplete partition type 2 (IP2) of the cochlea and a dilated vestibule, which together constitute Mondini malformation. Pathogenic SLC26A4 variants are considered the major cause of inner ear malformation but the genetics still needs clarification. The aim of this study was to identify the cause of EVA in patients with hearing loss (HL). Genomic DNA was isolated from HL patients with radiologically confirmed bilateral EVA (n = 23) and analyzed by next generation sequencing using a custom HL gene panel encompassing 237 HL-related genes or a clinical exome. The presence and segregation of selected variants and the CEVA haplotype (in the 5' region of SLC26A4) was verified by Sanger sequencing. Minigene assay was used to evaluate the impact of novel synonymous variant on splicing. Genetic testing identified the cause of EVA in 17/23 individuals (74%). Two pathogenic variants in the SLC26A4 gene were identified as the cause of EVA in 8 of them (35%), and a CEVA haplotype was regarded as the cause of EVA in 6 of 7 patients (86%) who carried only one SLC26A4 genetic variant. In two individuals with a phenotype matching branchio-oto-renal (BOR) spectrum disorder, cochlear hypoplasia resulted from EYA1 pathogenic variants. In one patient, a novel variant in CHD7 was detected. Our study shows that SLC26A4, together with the CEVA haplotype, accounts for more than half of EVA cases. Syndromic forms of HL should also be considered in patients with EVA. We conclude that to better understand inner ear development and the pathogenesis of its malformations, there is a need to look for pathogenic variants in noncoding regions of known HL genes or to link them with novel candidate HL genes.

Analysis of SLC26A4, FOXI1, and KCNJ10 Gene Variants in Patients with Incomplete Partition of the Cochlea and Enlarged Vestibular Aqueduct (EVA) Anomalies

Pathogenic variants in the SLC26A4, FOXI1, and KCNJ10 genes are associated with hearing loss (HL) and specific inner ear abnormalities (DFNB4). In the present study, phenotype analyses, including clinical data collection, computed tomography (CT), and audiometric examination, were performed on deaf individuals from the Sakha Republic of Russia (Eastern Siberia). In cases with cochleovestibular malformations, molecular genetic analysis of the coding regions of the SLC26A4, FOXI1, and KCNJ10 genes associated with DFNB4 was completed. In six of the 165 patients (3.6%), CT scans revealed an incomplete partition of the cochlea (IP-1 and IP-2), in isolation or combined with an enlarged vestibular aqueduct (EVA) anomaly. Sequencing of the SLC26A4, FOXI1, and KCNJ10 genes was performed in these six patients. In the SLC26A4 gene, we identified four variants, namely c.85G>C p.(Glu29Gln), c.757A>G p.(Ile253Val), c.2027T>A p.(Leu676Gln), and c.2089+1G>A (IVS18+1G>A), which are known as pathogenic, as well as c.441G>A p.(Met147Ile), reported previously as a variant with uncertain significance. Using the AlphaFold algorithm, we found in silico evidence of the pathogenicity of this variant. We did not find any causative variants in the FOXI1 and KCNJ10 genes, nor did we find any evidence of digenic inheritance associated with double heterozygosity for these genes with monoallelic SLC26A4 variants. The contribution of biallelic SLC26A4 variants in patients with IP-1, IP-2, IP-2+EVA, and isolated EVA was 66.7% (DFNB4 in three patients, Pendred syndrome in one patient). Seventy-five percent of SLC26A4-biallelic patients had severe or profound HL. The morphology of the inner ear anomalies demonstrated that, among SLC26A4-biallelic patients, all types of incomplete partition of the cochlea are possible, from IP-1 and IP-2, to a normal cochlea. However, the dominant type of anomaly was IP-2+EVA (50.0%). This finding is very important for cochlear implantation, since the IP-2 anomaly does not have an increased risk of “gushers” and recurrent meningitis.

SLC26A4 Phenotypic Variability Influences Intra- and Inter-Familial Diagnosis and Management

SLC26A4 is one of the most common genes causing autosomal recessive non-syndromic sensorineural hearing loss (SNHL). It has been reported to cause Pendred Syndrome (PDS) and DFNB4 which is deafness with enlarged vestibular aqueduct (EVA). However, mutated SLC26A4 is not conclusive for having either DFNB4 or PDS. Three unrelated Jordanian families consisting of eight affected individuals with congenital bilateral hearing loss (HL) participated in this study. Whole-exome and Sanger sequencing were performed to investigate the underlying molecular etiology of HL. Further clinical investigations, including laboratory blood workup for the thyroid gland, CT scan for the temporal bone, and thyroid ultrasound were performed. Three disease-causing variants were identified in SLC26A4 in the three families, two of which were novel. Two families had a novel pathogenic homozygous splice-site accepter variant (c.165-1G>C), while the third family had compound heterozygous pathogenic variants (c.1446G>A; p.Trp482* and c.304G>A; p.Gly102Arg). Our approach helped in redirecting the diagnosis of several affected members of three different families from non-syndromic HL to syndromic HL. Two of the affected individuals had typical PDS, one had DFNB4, while the rest had atypical PDS. Our work emphasized the intra- and inter-familial variability of SLC26A4-related phenotypes. In addition, we highlighted the variable phenotypic impact of SLC26A4 on tailoring a personalized healthcare management.

Enlarged Vestibular Aqueduct: Disease Characterization and Exploration of Potential Prognostic Factors for Cochlear Implantation

OBJECTIVES

There is an unmet need to match the anticipated natural history of hearing loss (HL) in enlarged vestibular aqueduct (EVA) with clinical management strategies. The objectives of this study are therefore to provide a detailed case characterization of an EVA cohort and explore the relationship between candidate prognostic factors and timing of cochlear implant (CI) surgery.

STUDY DESIGN

A multicenter retrospective review of patients diagnosed with EVA.

SETTING

Patient data recruitment across three CI centers in the UK.

PATIENTS

One hundred fifty patients with a radiological diagnosis of EVA from January 1995 to January 2021.

MAIN OUTCOME MEASURES

Age at audiological candidacy for CI and age at first implant surgery.

RESULTS

EVA was predominately a bilateral condition (144/ 150) with increased prevalence in women (M:F, 64:86). 51.7% of patients failed new-born hearing screening, with 65.7% having HL diagnosed by 1 year. Initial moderate to severe and severe to profound HL were reported most frequently. In 123 patients, median age that audiological candidacy for CI was met for at least one ear was 2.75 years. Median age at first CI was 5 years (140/150).Pendred syndrome (confirmed in 73 patients) and ethnicity, were not significantly associated with earlier CI surgery. Multivariate linear regression demonstrated that male patients have first CI surgery significantly earlier than females (coefficient -0.43, 95% CI [-0.82, -0.05), p-value = 0.028).

CONCLUSIONS

This large UK EVA cohort provides evidence that patients should be closely monitored for CI candidacy within the first 3 years of life. Significantly, male gender is emerging as an independent prognostic factor for earlier assessment and first CI surgery.

Prediction of Hearing Prognosis of Large Vestibular Aqueduct Syndrome Based on the PyTorch Deep Learning Model

In order to compare magnetic resonance imaging (MRI) findings of patients with large vestibular aqueduct syndrome (LVAS) in the stable hearing loss (HL) group and the fluctuating HL group, this paper provides reference for clinicians' early intervention. From January 2001 to January 2016, patients with hearing impairment diagnosed as LVAS in infancy in the Department of Otorhinolaryngology, Head and Neck Surgery, Children's Hospital of Fudan University were collected and divided into the stable HL group (n = 29) and the fluctuating HL group (n = 30). MRI images at initial diagnosis were collected, and various deep learning neural network training models were established based on PyTorch to classify and predict the two series. Vgg16_bn, vgg19_bn, and ResNet18, convolutional neural networks (CNNs) with fewer layers, had favorable effects for model building, with accs of 0.9, 0.8, and 0.85, respectively. ResNet50, a CNN with multiple layers and an acc of 0.54, had relatively poor effects. The GoogLeNet-trained model performed best, with an acc of 0.98. We conclude that deep learning-based radiomics can assist doctors in accurately predicting LVAS patients to classify them into either fluctuating or stable HL types and adopt differentiated treatment methods.

Novel CRISPR/Cas12a-based genetic diagnostic approach for SLC26A4 mutation-related hereditary hearing loss

Hereditary hearing loss is a common defect of the auditory nervous system with high-incidence, seriously affecting the quality of life of the patients. The clinical manifestations of SLC26A4 mutation-related hearing loss are congenital sensorineural or mixed deafness. Sensitive and specific SLC26A4 mutation detection in the early clinical stage is key for the early indication of potential hearing loss in the lack of effective treatment. Using clustered regularly interspaced short palindromic repeats (CRISPR)-based nucleic acid detection technology, we designed a fast and sensitive detection system for SLC26A4 pathogenic mutations (c.919-2A > G, c.2168A > G and c.1229C > T). This recombinase-aided amplification-based detection system allows rapid target gene amplification and, in combination with the CRISPR-based nucleic acid testing (NAT) system, mutation site detection. Moreover, mismatches were introduced in CRISPR-derived RNA (crRNA) to increase signal differences between the wild-type genes and mutant genes. A total of 64 samples were examined using this approach and all results were verified using Sanger sequencing. The detection results were consistent with the polymerase chain reaction-Sanger sequencing results. Overall, this CRISPR-based NAT technology provides a sensitive and fast new approach for the detection of hereditary deafness and provides a crRNA optimization strategy for single-nucleotide polymorphism detection, which could be helpful for the clinical diagnosis of SLC26A4 mutation-related hereditary hearing loss.

Vestibular Function in Pendred Syndrome: Intact High Frequency VOR and Saccular Hypersensitivity

OBJECTIVE

Although Pendred syndrome involves anatomical abnormalities in the vestibular system and patient-perceived dizziness, the literature on vestibular function is scarce. The objective was to evaluate objective vestibular function in patients with PS using the video head impulse test (VHIT) and the cervical vestibular evoked myogenic potential (cVEMP) test, assessing the high frequency vestibulo-ocular reflex (VOR) and the saccular function, respectively.

METHODS

Twenty-six subjects (52 ears) with Pendred Syndrome and severe-to-profound hearing loss (cochlear implant candidacy) were studied retrospectively. Main outcome measures were VHIT VOR gain, refixation saccades, cVEMP stimulus thresholds and amplitudes.

RESULTS

In total, 4 of 52 ears (8%) had pathological VHIT outcomes (2 ears with low VHIT gain and 2 ears with saccades). The mean VHIT gain value was 0.96 (range 0.63-2.02). No patients had complete VOR loss. CVEMP responses were present in 76% of tested ears and absent in 24%. The mean cVEMP amplitude value was 192 μV. Absence of cVEMP response was associated with the presence of VHIT saccades (p = 0.038) and advanced age (rs = -0.34; p < 0.05). cVEMP amplitude was correlated with VHIT gain (rs = 0.46; p < 0.001).

CONCLUSION

Despite dysmorphic vestibular anatomy and severe loss of hearing, the VHIT VOR function is normal in patients with Pendred Syndrome. However, saccular function appears to be abnormally sensitive, as documented by low cVEMP thresholds and high amplitudes, which agrees with a "third window" effect secondary to the large vestibular aqueduct.

Powerful use of automated prioritization of candidate variants in genetic hearing loss with extreme etiologic heterogeneity

Variant prioritization of exome sequencing (ES) data for molecular diagnosis of sensorineural hearing loss (SNHL) with extreme etiologic heterogeneity poses a significant challenge. This study used an automated variant prioritization system (“EVIDENCE”) to analyze SNHL patient data and assess its diagnostic accuracy. We performed ES of 263 probands manifesting mild to moderate or higher degrees of SNHL. Candidate variants were classified according to the 2015 American College of Medical Genetics guidelines, and we compared the accuracy, call rates, and efficiency of variant prioritizations performed manually by humans or using EVIDENCE. In our in silico panel, 21 synthetic cases were successfully analyzed by EVIDENCE. In our cohort, the ES diagnostic yield for SNHL by manual analysis was 50.19% (132/263) and 50.95% (134/263) by EVIDENCE. EVIDENCE processed ES data 24-fold faster than humans, and the concordant call rate between humans and EVIDENCE was 97.72% (257/263). Additionally, EVIDENCE outperformed human accuracy, especially at discovering causative variants of rare syndromic deafness, whereas flexible interpretations that required predefined specific genotype–phenotype correlations were possible only by manual prioritization. The automated variant prioritization system remarkably facilitated the molecular diagnosis of hearing loss with high accuracy and efficiency, fostering the popularization of molecular genetic diagnosis of SNHL.

Phoniatric, Audiological, Orodental and Speech Problems in a Boy with Cardio-Facio-Cutaneous Syndrome Type 3 (CFC 3) Due to a Pathogenic Variant in MAP2K1 - Case Study

Cardio-facio-cutaneous syndrome 3 (CFC3) due to variants in MAP2K1 is a rare genetic disorder manifested mainly by short stature, facial dysmorphism, abnormalities of the cardiovascular system, skin changes, and intellectual disability. The aim of the study is the evaluation of the occurrence of pathological changes in the upper respiratory tract, orthodontic disorders, as well as voice, speech and hearing abnormalities in an 11-year-old boy with CFC3 syndrome. The lack of detailed diagnostics of speech, voice and hearing disorders, as well as the degree of their severity was an inspiration to undertake research in this field. Pathological changes in face, oral cavity, upper respiratory tract (nose, nasopharynx, larynx), and hearing organ, as well as voice and speech quality, were assessed in an 11-year-old boy with CFC3 syndrome. Pathologies of the upper respiratory tract (adenoid hypertrophy, narrowing of the nasal passages) and laryngeal asymmetry were found without significant changes in voice quality in the acoustic examination, except for the voice timbre change confirmed in narrowband spectrography. Complex audiological assessment confirmed the existence of bilateral sensorineural hearing loss. Speech pathology assessment revealed abnormalities in the structure of articulation organ, its decreased motor efficiency, imprecision, reduced coordination, as well as the presence of autistic features. Exome sequencing showed the heterozygous variant c.371C>T (p.Pro124Leu) in the MAP2K1 gene, previously described as pathogenic, thus supporting a causative relevance. Phoniatric, audiological, orodental and speech problems should be considered as features of cardio-facio-cutaneous syndrome type 3 (CFC 3) phenotype due to a pathogenic variant in MAP2K1.

Genetic Determinants of Non-Syndromic Enlarged Vestibular Aqueduct: A Review

Hearing loss is the most common sensorial deficit in humans and one of the most common birth defects. In developed countries, at least 60% of cases of hearing loss are of genetic origin and may arise from pathogenic sequence alterations in one of more than 300 genes known to be involved in the hearing function. Hearing loss of genetic origin is frequently associated with inner ear malformations; of these, the most commonly detected is the enlarged vestibular aqueduct (EVA). EVA may be associated to other cochleovestibular malformations, such as cochlear incomplete partitions, and can be found in syndromic as well as non-syndromic forms of hearing loss. Genes that have been linked to non-syndromic EVA are SLC26A4, GJB2, FOXI1, KCNJ10, and POU3F4. SLC26A4 and FOXI1 are also involved in determining syndromic forms of hearing loss with EVA, which are Pendred syndrome and distal renal tubular acidosis with deafness, respectively. In Caucasian cohorts, approximately 50% of cases of non-syndromic EVA are linked to SLC26A4 and a large fraction of patients remain undiagnosed, thus providing a strong imperative to further explore the etiology of this condition.

Exploring the missing heritability in subjects with hearing loss, enlarged vestibular aqueducts, and a single or no pathogenic SLC26A4 variant

Pathogenic variants in SLC26A4 have been associated with autosomal recessive hearing loss (arHL) and a unilateral or bilateral enlarged vestibular aqueduct (EVA). SLC26A4 is the second most frequently mutated gene in arHL. Despite the strong genotype–phenotype correlation, a significant part of cases remains genetically unresolved. In this study, we investigated a cohort of 28 Dutch index cases diagnosed with HL in combination with an EVA but without (M0) or with a single (M1) pathogenic variant in SLC26A4. To explore the missing heritability, we first determined the presence of the previously described EVA-associated haplotype (Caucasian EVA (CEVA)), characterized by 12 single nucleotide variants located upstream of SLC26A4. We found this haplotype and a delimited V1-CEVA haplotype to be significantly enriched in our M1 patient cohort (10/16 cases). The CEVA haplotype was also present in two M0 cases (2/12). Short- and long-read whole genome sequencing and optical genome mapping could not prioritize any of the variants present within the CEVA haplotype as the likely pathogenic defect. Short-read whole-genome sequencing of the six M1 cases without this haplotype and the two M0/CEVA cases only revealed previously overlooked or misinterpreted splice-altering SLC26A4 variants in two cases, who are now genetically explained. No deep-intronic or structural variants were identified in any of the M1 subjects. With this study, we have provided important insights that will pave the way for elucidating the missing heritability in M0 and M1 SLC26A4 cases. For pinpointing the pathogenic effect of the CEVA haplotype, additional analyses are required addressing defect(s) at the RNA, protein, or epigenetic level.

Genetic Susceptibility Study of Chinese Sudden Sensorineural Hearing Loss Patients with Vertigo

OBJECTIVE

To investigate the genetic causes of sudden sensorineural hearing loss (SSNHL) patients in China. This study focused on analyzing variations of coding sequence of common genes related to deafness, revealing the molecular pathogenesis of sudden deafness from a genomics perspective, discovering molecular markers associated with the onset of deafness, and then supplying prevention to high-risk populations, classifying disease according to accurate etiology, and choosing a much more precision therapy.

METHODS

We retrospectively analyzed the clinical characteristics of 51 patients diagnosed as SSNHL with vertigo treated in the Chinese PLA General Hospital. In this study, mutation screening of 307 nuclear genes and mitochondrial genome responsible for human or mouse deafness was performed on the 51 cases of unilateral sudden deafness patients with vertigo.

RESULTS

We identified 51 cases of unilateral sudden deafness, including 2 cases of low-mid frequency hearing impairment, 18 cases of mid-high frequency hearing loss, 11 cases of flat-type hearing loss, and 20 cases of all frequency hearing loss. Among the 51 cases, 8 (15.69%) cases of GJB2 heterozygous variations, 1 (1.96%) case of GJB3 heterozygous variations, 5 (9.8%) cases of SLC26A4 heterozygous variations, 2 (3.92%) cases of COCH heterozygous variations, 14 (27.45%) cases of CDH23 heterozygous variations, 14 (27.45%) cases of OTOF heterozygous variations, 1 (1.96%) case of SLC17A8 heterozygous variations and 2 (3.92%) cases of KCNE1 heterozygous variations. No mtDNA gene variations were identified.

CONCLUSION

SSNHL has some relationship with hereditary in Chinese population, but its complex genetic pathogenic mechanisms need further study.

Genetic architecture and phenotypic landscape of SLC26A4-related hearing loss

Mutations of coding regions and splice sites of SLC26A4 cause Pendred syndrome and nonsyndromic recessive hearing loss DFNB4. SLC26A4 encodes pendrin, a transmembrane exchanger of anions and bases. The mutant SLC26A4 phenotype is characterized by inner ear malformations, including an enlarged vestibular aqueduct (EVA), incomplete cochlear partition type II and modiolar hypoplasia, progressive and fluctuating hearing loss, and vestibular dysfunction. A thyroid iodine organification defect can lead to multinodular goiter and distinguishes Pendred syndrome from DFNB4. Pendred syndrome and DFNB4 are each inherited as an autosomal recessive trait caused by biallelic mutations of SLC26A4 (M2). However, there are some EVA patients with only one detectable mutant allele (M1) of SLC26A4. In most European-Caucasian M1 patients, there is a haplotype that consists of 12 variants upstream of SLC26A4, called CEVA (Caucasian EVA), which acts as a pathogenic recessive allele in trans to mutations affecting the coding regions or splice sites of SLC26A4. This combination of an M1 genotype with the CEVA haplotype is associated with a less severe phenotype than the M2 genotype. The phenotype in EVA patients with no mutant alleles of SLC26A4 (M0) has a very low recurrence probability and is likely to be caused by other factors.

Feingold syndrome type 2 in a patient from China

Feingold syndrome type 2 (FGLDS2, MIM614326) is a genetic congenital malformation syndrome, caused by germline heterozygous deletion of MIR17HG on chromosome 13q31, which is extremely rare worldwide. To date, less than 25 patients have been described in the literature. Here, we report on a 3-year-old girl presented with hip dysplasia, polysyndactyly of the left thumb, brachymesophalangy of the fifth digit, microcephaly, intellectual disability, and growth delay. This is likely to be the first case of Feingold syndrome type 2 ever discovered among Chinese population. Through genetic testing and pedigree analysis, she was identified to have a de novo 4.8-Mb microdeletion at chromosome 13q31.3-q32.1, encompassing MIR17HG, GPC5, and GPC6. Additionally, we detected two common compound heterozygous variants (c.919-2A>G and c.147C>G) in SLC26A4 encoding pendrin protein, as well as a novel heterozygous variant c.985_988del in COMP encoding cartilage oligomeric matrix protein. This case report aims to analyze the microdeletion and the three types of variant detected in the patient, and to explore the association between the genotype and phenotype in patients with Feingold syndrome type 2, which may contribute to further understanding and future diagnosis of this disorder.

Nonsyndromic Congenital Causes of Sensorineural Hearing Loss in Children: An Illustrative Review

OBJECTIVE. The purpose of this article is to provide an illustrative review of nonsyndromic congenital causes of sensorineural hearing loss (SNHL) in children. CONCLUSION. Early recognition and treatment are essential in maximizing developmental outcomes in children with congenital SNHL. Because imaging plays an integral role in identifying underlying causes of SNHL, it is imperative that radiologists be able to recognize, describe, and appropriately categorize the spectrum of congenital inner ear malformations in children.

Investigation of DFNB4 SLC26A4 mutation in patients with enlarged vestibular aquaduct

OBJECTIVES

Mutations of the SLC26A4 gene causing enlarged vestibular aqueduct (EVA) syndrome have not yet been fully elucidated. The study aimed to investigate SLC26A4 mutations in patients with EVA syndrome in the Turkish population. Identifying these mutations may play an essential role in determining the prognosis, follow-up, and management options of these patients.

METHODS

Whole exome sequencing and/or Sanger sequencing of SLC26A4 in 22 patients with sensorineural hearing loss associated with isolated EVA without inner ear anomalies, and 22 controls were performed.

RESULTS

Twenty-two patients and 22 control subjects were included in the study. The onset of hearing loss was pre-lingual in 15 patients, and post-lingual in 7. The mean (standard deviation) vestibular aqueduct width of the patients was 3.23 mm (1.28). Twenty SLC26A4 variants, 15 of them unique, were identified in 22 patients. Among them, seven variants were heterozygous, and 13 were homozygous. The variants p.E37X (c.109G > T), p.Y27H (c.79T > C), p.C706Y (c.2117G > A) have not been previously reported.

CONCLUSION

The detection of rare and previously unreported mutations in our study showed that studies with a larger number of patients with EVA might reveal more role of the SLC26A4 gene. Besides, to understand the etiopathogenesis of the disease, other related genes also should be investigated.

Enlarged vestibular aqueduct and Mondini Malformation: audiological, clinical, radiologic and genetic features

PURPOSE

When referring to enlarged vestibular aqueduct (EVA) we should differentiate between nonsyndromic enlarged vestibular aqueduct (NSEVA) and Pendred Syndrome (PDS), a disease continuum associated with pathogenic sequence variants of Pendrin's Gene (SLC26A4) in about half of the cases. The study was aimed to analyse the clinical and audiological features of a monocentric cohort of Caucasian patients with NSEVA/PDS, their genetic assessment and morphological inner ear features.

METHODS

We retrospectively reviewed the audiologic, genetic and anamnestic data of 66 patients with NSEVA/PDS followed by our audiology service.

RESULTS

SLC26A4 mutations was significantly correlated with the presence of PDS rather than NSEVA (p < 0.019), with the expression of inner ear malformations (p < 0.001) and with different severity of hearing loss (p = 0.001). Furthermore, patients with PDS showed significantly worse pure tone audiometry (PTA) than patients with NSEVA (p = 0.001). Anatomically normal ears presented significantly better PTA than ears associated with Mondini Malformation or isolated EVA (p < 0.001), but no statistically significative differences have been observed in PTA between patients with Mondini Malformation and isolated EVA.

CONCLUSION

NSEVA/PDS must be investigated in all the congenital hearing loss, but also in progressive, late onset, stepwise forms. Even mixed or fluctuating hearing loss may constitute a sign of a NSEVA/PDS pathology. Our findings can confirm the important role of SLC26A4 mutations in determining the phenotype of isolated EVA/PDS, both for the type/degree of the malformation, the hearing impairment and the association with thyroid dysfunction.

The Natural History of Hearing Loss in Pendred Syndrome and Non-Syndromic Enlarged Vestibular Aqueduct

INTRODUCTION

The aim was to investigate the progress of hearing loss over time in a cohort of pendred syndrome and non-syndromic enlarged vestibular aqueduct (PS/NSEVA) with one or two confirmed pathogenic variations in SLC26A4.

STUDY DESIGN

Retrospective cohort study.

SUBJECTS AND METHODS

At our tertiary referral center, a retrospective search of all patients with enlarged vestibular aqueduct, hearing loss and SLC26A4 mutations yielded 103 individuals by March 2017, 96 of whom had records of hearing levels; both an early audiometry and the latest between 3 and 668 months follow-up. Pure-tone average (PTA; average of thresholds at 0.5, 1, 2 and 4 kHz) was calculated for both ears at time 1 and time 2. Neonatal screening results were retrieved.

RESULTS

Eighty-seven (87) individuals had biallelic (M2) and 16 had monoallelic alterations (M1) in their SLC26A4. On average, the PTA progressed to 80 dB HL by the age of 6 years for the entire cohort, and 3.2 years for the biallelic (M2) affected individuals. 25% of the cohort was screened in the neonatal screening program; of these 42% had "passed" at least monaurally. Audiometric profiles related to age show faster deterioration in high frequencies than in low frequencies.

CONCLUSION

In patients with PS/NSEVA and SLC26A4 mutations, the average hearing loss progresses to 80 dB HL by the age of 6 years. For biallelic (M2) affected individuals it was 3.2 years. Although hearing levels reached severe to profound during childhood, almost 1/2 had passed neonatal hearing screening, at least monaurally, emphasizing the need for close follow-up.