Consanguinity Among Parents of Iranian Deaf Children

Hearing Loss Among Families with 2 and More Affected Members in Golestan Province, Iran: A Cross-Sectional Study of 320 Families

BACKGROUND

Our study centers on various aspects of families who have 2 or more members with hearing loss (HL) and are living in Golestan province in Iran. We aimed to identify those families with the highest probability of hereditary HL and also to examine the impact of consanguinity among them.

METHODS

The families included in the study underwent a comprehensive screening process that involved their prenatal and postnatal histories as well as family medical histories. Additionally, each patient received a thorough clinical ear examination. The evaluation also took into account factors such as patterns of inheritance, consanguinity, a 3-generation pedigree, and physical examination. Following this initial assessment, patients were referred for a complete hearing evaluation, which included pure-tone audiometry, speech recognition threshold, otoacoustic emission, and auditory brainstem response tests.

RESULTS

We identified a total of 8553 individuals living in Golestan province who are hearing impaired. Among those, our records indicate that 320 families had at least 2 affected members. The rate of consanguinity marriage in non-syndromic families was 64.43%. Also, a significant number (88.12%, or n=282) of the families exhibited hereditary HL, among which a substantial proportion (89.72%, or n=253) presented with nonsyndromic forms of HL. Furthermore, bilateral, stable, and prelingual HL were the most frequently observed types, and a majority of the patients were diagnosed with sensorineural and profound HL.

CONCLUSION

This study revealed a correlation between consanguinity and the incidence of familial HL, with more probability of bilateral, prelingual, sensorineural, and profound forms.

Parental Consanguinity and Risk for Childhood Hearing Loss: A Retrospective Cohort Study

INTRODUCTION

Genetic causes are responsible for half of the cases of hearing loss, most of them being the result of non-syndromic genetic changes resulting from autosomal recessive inheritance. Parental consanguinity might be an indicator to consider in the diagnosis of these cases. The aim of this study was to assess its importance as a risk factor for childhood hearing loss.

MATERIAL AND METHODS

A retrospective cohort study conducted in a district hospital, between 2014 and 2018. We included all live births born during this period and excluded those with risk factors for childhood hearing loss other than parental consanguinity and those without hearing screening. We formed two study groups: newborns with parental consanguinity and newborns without risk factors. All the participants underwent hearing screening with the primary outcome of this study being the result of the screening. Those with a not normal result or with parental consanguinity also underwent diagnostic audiological evaluation.

RESULTS

Among 8513 live births, we studied 96 newborns with first-degree parental consanguinity and 96 newborns without risk factors. We found a statistically significant difference (p = 0.007) between the groups, with a 'refer' screening result rate of 24% in the group with parental consanguinity and 9.4% in the group without risk factors. We diagnosed one case of sensorineural hearing loss and another of mixed hearing loss in the first group and none of these cases in the second.

CONCLUSION

Parental consanguinity was associated with a higher risk of a refer screening result in newborns, which suggests the need to consider this as a risk factor for childhood hearing loss.

Reporting Two Novel Mutations in Two Iranian Families with Cystic Fibrosis, Molecular and Bioinformatic Analysis

Background

Cystic fibrosis (CF) is the most common heredity disease among the Caucasian population. More than 350 known pathogenic variations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene (NM_000492.4) cause CF. Herein, we report the outcome of our investigation in two unrelated Iranian families with CF patients.

Methods

We conducted phenotypic examination, segregation, linkage analysis, and CFTR gene sequencing to define causative mutations.

Results

We found two novel mutations in the present study. The first one was a deletion causing frameshift, c.299delT p.(Leu100Profs*7), and the second one was a missense mutation, c.1857G>T, at nucleotide binding domain 1 of the CFTR protein. Haplotype segregation data supported our new mutation findings.

Conclusion

Findings of this study expand the spectrum of CFTR pathogenic variations and can improve prenatal diagnosis and genetic counseling for CF.

Determination risk factors for severe and profound hearing loss in child candidates for cochlear implantation in southeast of Iran during 2014-2020

Background

Hearing loss can have a major impact on children’s language development, academic success and hearing comprehension. The aim of the present study was to determinate risk factors for severe and profound hearing loss in child candidates for cochlear implantation in southeast of Iran during 2014–2020.

Materials and methods

This case-control study consisted of 400 children referring to a cochlear implant center (in southeastern Iran) from Bandar Abbas, Zahedan and Kerman during the years 2014–2020 as cases. The subjects were selected using the random sampling method; 200 children hospitalized in Shafa and Afzalipour hospitals were selected as controls.

Results

Based on the results of the multivariate logistic regression, weight less than 1500 g (OR = 4.40: p < 0.05), hospitalization in NICU (OR = 7.21: p < 0.05), family history of hearing loss (OR = 11.47: p < 0.05), Gestational age over 35 (OR = 9.63: p < 0.05), intracranial hemorrhage (OR = 5.18: p < 0.05), consanguineous marriage (OR = 12.48: p < 0.05) and high fever and seizures (OR = 3.02: p < 0.05) were recognized as risk factors for sensorineural deafness in children.

Conclusion

Most of the risk factors for deafness are preventable, and hereditary factors play an important role in congenital deafness in children. Therefore, genetic counseling before consanguineous marriage, early diagnosis, timely intervention can prevent many cases of hearing loss in children.

Next-Generation Sequencing Identifies Pathogenic Variants in HGF, POU3F4, TECTA, and MYO7A in Consanguineous Pakistani Deaf Families

Background

Approximately 70% of congenital deafness is attributable to genetic causes. Incidence of congenital deafness is known to be higher in families with consanguineous marriage. In this study, we investigated the genetic causes in three consanguineous Pakistani families segregating with prelingual, severe-to-profound deafness.

Results

Through targeted next-generation sequencing of 414 genes known to be associated with deafness, homozygous variants c.536del (p. Leu180Serfs∗20) in TECTA, c.3719 G>A (p. Arg1240Gln) in MYO7A, and c.482+1986_1988del in HGF were identified as the pathogenic causes of enrolled families. Interestingly, in one large consanguineous family, an additional c.706G>A (p. Glu236Lys) variant in the X-linked POU3F4 gene was also identified in multiple affected family members causing deafness. Genotype-phenotype cosegregation was confirmed in all participating family members by Sanger sequencing.

Conclusions

Our results showed that the genetic causes of deafness are highly heterogeneous. Even within a single family, the affected members with apparently indistinguishable clinical phenotypes may have different pathogenic variants.

Investigation of MYO15A and MYO7A Mutations in Iranian Patients with Nonsyndromic Hearing Loss

Hearing loss (HL) is the most common sensory disorder in humans, which affects individuals in both inherited and acquired forms. MYO15A and MYO7A gene mutations have a significant role in the development of deafness. In this study, we assessed the prevalence of MYO15A and MYO7A mutations in one hundred non-relative deaf Iranians. Materials and methods: The existence of MYO15A and MYO7A mutations were assessed using the tetra-primer ARMS-PCR method, High Resolution Melting (HRM) and sequencing method. Results: A heterozygote missense mutation, p.V2135L (c.6403G > T) in the MYO15A gene, was found in a patient using the sequencing method. Conclusion: These results explain the negligible prevalence of selected mutations among Iranian patients. Identifying common mutations in patients of an ethnic group can reduce the financial costs and time needed for identifying the causes of deafness.

Familial-Related Risks for Congenital Hypothyroidism in Iranian Newborns: A Population-Based Case-Control Study

BACKGROUND

Congenital hypothyroidism (CH), as one of the most common endocrine disorders, is a preventable cause of mental retardation.

OBJECTIVE

This study aimed to identify familial-related risk factors for CH in Iranian newborns.

METHODS

A population-based case-control study was performed on the National Registry System of patients with CH in Iran. In this study, 906 controls and 454 cases were studied for one year. Familial related factors were investigated using logistic regression models. Population attributable fraction (PAF) was also calculated for each significant risk factor.

RESULTS

Using multivariate analysis, an increased risk for CH was observed in patients with congenital anomalies (odds ratio (OR): 5.77, 95% confidence interval (CI): 2.37 - 14.01), history of mental retardation in family (OR:2.10, 95% CI: 1.15-3.83), mother's hypothyroidism during pregnancy (OR: 2.01, 95% CI: 1.33 - 3.03), intra-family marriage (OR:1.49, 95% CI: 1.18 - 1.89), gestational diabetes (OR: 1.69, 95% CI: 1.09 - 2.63), having a hypothyroid child in the family (OR: 2.48, 95% CI: 1.39 - 4.42), and twins or more (OR: 2.61, 95% CI: 1.31 - 5.21). The highest PAF among familial-related risk factors for CH is related to the intra-family marriage (14.9%).

CONCLUSIONS

This study revealed that familial-related risk factors and consanguine marriages play an essential role in the high incidence of CH in Iran. About 15% of CH in Iran could be attributed to intra-family marriage alone.

Identification of novel variants in Iranian consanguineous pedigrees with nonsyndromic hearing loss by next-generation sequencing

Background

The extremely high genetic heterogeneity of hearing loss due to diverse group of genes encoding proteins required for development, function, and maintenance of the complex auditory system makes the genetic diagnosis of this disease challenging. Up to now, 121 different genes have been identified for nonsyndromic hearing loss (NSHL), of which 76 genes are responsible for the most common forms of NSHL, autosomal recessive nonsyndromic hearing loss (ARNSHL).

Methods

After excluding mutations in the most common ARNSHL gene, GJB2, by Sanger sequencing, genetic screening for a panel of genes responsible for hereditary hearing impairment performed in 9 individuals with ARNSHL from unrelated Iranian consanguineous pedigrees.

Results

One compound heterozygote and eight homozygote variants, of which five are novel, were identified: CDH23:p.(Glu1970Lys), and p.(Ala1072Asp), GIPC3:p.(Asn82Ser), and (p.Thr41Lys), MYO7A:p.[Phe456Phe]; p.[Met708Val], and p.(Gly163Arg), TECTA:p.(Leu17Leufs*19), OTOF:c.1392+1G>A, and TRIOBP:p.(Arg1068*). Sanger sequencing confirmed the segregation of the variants with the disease in each family.

Conclusion

Finding more variants and expanding the spectrum of hearing impairment mutations can increase the diagnostic value of molecular testing in the screening of patients and can improve counseling to minimize the risk of having affected children for at risk couples.

The conserved p.Arg108 residue in S1PR2 (DFNB68) is fundamental for proper hearing: evidence from a consanguineous Iranian family

BACKGROUND

Genetic heterogeneity and consanguineous marriages make recessive inherited hearing loss in Iran the second most common genetic disorder. Only two reported pathogenic variants (c.323G>C, p.Arg108Pro and c.419A>G, p.Tyr140Cys) in the S1PR2 gene have previously been linked to autosomal recessive hearing loss (DFNB68) in two Pakistani families. We describe a segregating novel homozygous c.323G>A, p.Arg108Gln pathogenic variant in S1PR2 that was identified in four affected individuals from a consanguineous five generation Iranian family.

METHODS

Whole exome sequencing and bioinformatics analysis of 116 hearing loss-associated genes was performed in an affected individual from a five generation Iranian family. Segregation analysis and 3D protein modeling of the p.Arg108 exchange was performed.

RESULTS

The two Pakistani families previously identified with S1PR2 pathogenic variants presented profound hearing loss that is also observed in the affected Iranian individuals described in the current study. Interestingly, we confirmed mixed hearing loss in one affected individual. 3D protein modeling suggests that the p.Arg108 position plays a key role in ligand receptor interaction, which is disturbed by the p.Arg108Gln change.

CONCLUSION

In summary, we report the third overall mutation in S1PR2 and the first report outside the Pakistani population. Furthermore, we describe a novel variant that causes an amino acid exchange (p.Arg108Gln) in the same amino acid residue as one of the previously reported Pakistani families (p.Arg108Pro). This finding emphasizes the importance of the p.Arg108 amino acid in normal hearing and confirms and consolidates the role of S1PR2 in autosomal recessive hearing loss.