Hearing loss secondary to variants in the OTOF gene.

OBJECTIVE: Genetic variants in the OTOF gene are responsible for non-syndromic hearing loss with an autosomal recessive inheritance pattern. The objective of our work was to evaluate the clinical characteristics of patients with biallelic pathogenic variants in OTOF and their evolution after treatment. METHODS: A cohort of 124 patients with prelingual hearing loss, studied from 1996 to 2023, was included in this study. A genetic analysis was conducted to identify the type and frequency of variants in the OTOF gene and their relation to the clinical characteristics of the patients. RESULTS: The homozygous p. Gln829* variant in the OTOF gene was detected in 3 probands (2.4 %) of a group 124 individuals with prelingual hearing loss. Another 6 family members to a total of 9 individuals were finally included. All presented with severe/profound bilateral sensorineural hearing loss of congenital onset. Three of these individuals were diagnosed with auditory neuropathy spectrum disorder. One individual passed the OAE test during the screening program, and since he did not have risk factors for hearing loss that would warrant ABR testing, this led to a delay in his hearing loss diagnosis. Four individuals underwent cochlear implants (three bilateral) with good functional outcomes. In three of them. However, in 17 familial cases with heterozygous variants, either no hearing loss was observed or it was within the expected range for their age. CONCLUSIONS: Hearing loss secondary to the p. Gln829* variant of the OTOF gene is relatively rare in our medical area. Its presence in homozygosity is the cause of severe/profound bilateral prelingual sensorineural hearing loss, responsible for auditory neuropathy with a good response to cochlear implantation.

Sensorineural Hearing Loss in Patients With the m.1555A>G Mutation in the MTRNR1 Gene.

OBJECTIVE: Mutations in the MTRNR1 gene of mitochondrial DNA are associated with non-syndromic hearing loss and increased susceptibility to aminoglycoside ototoxicity. The aim of our study was to determine the clinical characteristics of sensorineural hearing loss caused by the m.1555A>G mutation in MTRNR1. METHODS: An observational retrospective study of the m.1555A>G mutation was conducted in patients with suspected hereditary bilateral sensorineural hearing loss in the Department of Otolaryngology of the Marqués de Valdecilla University Hospital (Cantabria, Spain) and in 100 controls with normal hearing. RESULTS: The m.1555A>G mutation was found in 82 individuals from 20 different families and in none of the controls. Variable degrees of hearing loss were observed, ranging from normal hearing to profound deafness. Patients with a history of streptomycin administration exhibited significantly more pronounced hearing loss. The onset of hearing loss occurred from childhood to adulthood, with progression or stability over the years. No associated vestibular alterations or other clinical manifestations outside the ear were found. Two cochlear implant recipients showed significant improvement in speech comprehension. CONCLUSIONS: Patients with the m.1555A>G mutation in the MTRNR1 gene often develop bilateral, symmetric sensorineural hearing loss, predominantly affecting high frequencies, worsened by streptomycin administration. This mutation does not affect the vestibular function. The variability in the severity of hearing loss, the heterogeneity of phenotypic expression, and the presence of carrier individuals with normal hearing may indicate the existence of modifying factors, both environmental and genetic. Cochlear implantees showed a good response in terms of speech intelligibility. Genetic testing for this mutation is recommended in patients with a family history of hearing loss to prevent the use of aminoglycosides if the mutation is found. LEVEL OF EVIDENCE: 4 Laryngoscope, 2024.

Unilateral submandibular gland aplasia with ipsilateral sublingual gland hypertrophy presenting as a neck mass.

The congenital absence of the major salivary glands is a very infrequent disorder, in which several glands are usually involved at the same time. Sometimes this disorder can be associated with other developmental anomalies. The unilateral aplasia of the submandibular gland is an extremely rare finding with only 14 cases reported in the literature. Clinically, this kind of patients may complain of dryness of the mouth, difficulties in chewing and swallowing, severe periodontal disease or multiple caries, but usually they follow an asymptomatic course. Salivary gland aplasia can be diagnosed with a large variety of imaging techniques, which include computer tomography (CT), magnetic resonance imaging (MR), ultrasonography (US), sialography, or scintigraphy. In this paper we report a case of a patient referred to our department with a long term and progressive growing neck mass, who has an unilateral submandibular gland aplasia associated to an ipsilateral hypertrophy of the sublingual gland.

Auditory neuropathy in patients carrying mutations in the otoferlin gene (OTOF).

Inherited hearing impairment affects one in 2,000 newborns. Nonsyndromic prelingual forms are inherited mainly as autosomal recessive traits, for which 16 genes are currently known. Mutations in the genes encoding connexins 26 and 30 account for up to 50% of these cases. However, the individual contribution of the remaining genes to the whole remains undetermined. In addition, for most of the genes there is a need for studies on genotype-phenotype correlations, to identify distinctive clinical features which may direct the molecular diagnosis to specific genes. Here we present a mutation analysis and a genotype-phenotype correlation study on the gene encoding otoferlin (OTOF), responsible for the DFNB9 subtype of prelingual hearing impairment. Four novel mutations were identified: c.2122C>T (p.Arg708Ter), c.4275G>A (p.Trp1425Ter), c.4362+2T>G, and c.5860_5862delATC (p.Ile1954del). A total of 37 subjects with mutations in OTOF were studied clinically. They were phenotypically homogeneous, having profound hearing impairment with very early onset, as shown by pure-tone audiometry and auditory brainstem responses. Magnetic resonance imaging and computed tomography did not reveal any inner ear malformation. Unexpectedly, transient evoked otoacoustic emissions (TEOAEs) were present, either bilaterally or unilaterally in 11 subjects. Altogether, clinical data of these subjects met the diagnostic criteria of auditory neuropathy. A total of 10 subjects had been successfully provided with cochlear implants. The results of our study indicate that genetic diagnosis of subjects with auditory neuropathy and profound hearing impairment should be directed to the otoferlin gene. Our data are of concern to universal screening programs which use TEOAEs as the first detection test for hearing impairment in newborns, since this technique may overlook a nonnegligible proportion of cases.

[Familial susceptibility to aminoglycoside ototoxicity due to the A1555G mutation in the mitochondrial DNA]. / Predisposición familiar a la ototoxicidad de los aminoglucósidos debido a la mutación A1555G del ADN mitocondrial.

BACKGROUND AND OBJECTIVE: The A1555G mutation in the mitochondrial genome causes sensorineural hearing loss and familial aminoglycoside ototoxicity. PATIENTS AND METHOD: Screening for the A1555G mutation was performed on 72 patients with nonsyndromic sensorineural hearing loss. RESULTS: The A1555G mutation was identified in 15 patients (20.8%). All of them presented maternal relatives with deafness. Individuals with the A1555G mutation that had been treated with aminoglycosides developed more severe hearing loss. CONCLUSIONS: The A1555G mutation should be screened in individuals with maternal relatives with hearing loss before administering aminoglycosides.

[Prevalence of the A1555G MTDNA mutation in sporadic hearing-impaired patients without known history of aminoglycoside treatment]. / Prevalencia de la mutación A1555G del gen MTRNR1 en pacientes con hipoacusia postlocutiva sin antecedentes familiares de sordera.

INTRODUCTION: The A1555G mitochondrial DNA (mtDNA) mutation is responsible for maternally inherited non-syndromic hearing loss that is increased by aminoglycoside exposure. The objective of this study was to ascertain the frequency of the A1555G mutation among patients without family history of hearing loss or known exposition to aminoglycosides. METHODS: We screened for the mtDNA A1555G mutation in Spanish patients with sporadic sensorineural hearing impairment without a known family history of hearing loss or aminoglycoside exposition seen at the ENT Department in Sierrallana Hospital (Torrelavega, Cantabria, Spain) over a four-year period. RESULTS: A total of 219 patients with bilateral hearing loss were screened. Two of them (0.9%) had the A1555G mitochondrial DNA mutation. Both patients had a moderate bilateral sensorineural hearing loss for low frequency, and moderate to severe loss for high-frequency. CONCLUSIONS: The mtDNA A1555G mutation in patients with sensorineural hearing loss without family history of deafness or aminoglycoside ototoxicity is infrequent in our region. We should suspect this mutation in patients younger than 50 years old, with postlingual bilateral sensorineural hearing loss that is more pronounced at high frequency.

Mutation in TRMU related to transfer RNA modification modulates the phenotypic expression of the deafness-associated mitochondrial 12S ribosomal RNA mutations.

The human mitochondrial 12S ribosomal RNA (rRNA) A1555G mutation has been associated with aminoglycoside-induced and nonsyndromic deafness in many families worldwide. Our previous investigation revealed that the A1555G mutation is a primary factor underlying the development of deafness but is not sufficient to produce a deafness phenotype. However, it has been proposed that nuclear-modifier genes modulate the phenotypic manifestation of the A1555G mutation. Here, we identified the nuclear-modifier gene TRMU, which encodes a highly conserved mitochondrial protein related to transfer RNA (tRNA) modification. Genotyping analysis of TRMU in 613 subjects from 1 Arab-Israeli kindred, 210 European (Italian pedigrees and Spanish pedigrees) families, and 31 Chinese pedigrees carrying the A1555G or the C1494T mutation revealed a missense mutation (G28T) altering an invariant amino acid residue (A10S) in the evolutionarily conserved N-terminal region of the TRMU protein. Interestingly, all 18 Arab-Israeli/Italian-Spanish matrilineal relatives carrying both the TRMU A10S and 12S rRNA A1555G mutations exhibited prelingual profound deafness. Functional analysis showed that this mutation did not affect importation of TRMU precursors into mitochondria. However, the homozygous A10S mutation leads to a marked failure in mitochondrial tRNA metabolisms, specifically reducing the steady-state levels of mitochondrial tRNA. As a consequence, these defects contribute to the impairment of mitochondrial-protein synthesis. Resultant biochemical defects aggravate the mitochondrial dysfunction associated with the A1555G mutation, exceeding the threshold for expressing the deafness phenotype. These findings indicate that the mutated TRMU, acting as a modifier factor, modulates the phenotypic manifestation of the deafness-associated 12S rRNA mutations.

Unilateral submandibular gland aplasia with ipsilateral sublingualgland hypertrophy presenting as a neck mass

The congenital absence of the major salivary glands is a very infrequent disorder, in which several glands are usuallyinvolved at the same time. Sometimes this disorder can be associated with other developmental anomalies.The unilateral aplasia of the submandibular gland is an extremely rare finding with only 14 cases reported in theliterature. Clinically, this kind of patients may complain of dryness of the mouth, difficulties in chewing and swallowing,severe periodontal disease or multiple caries, but usually they follow an asymptomatic course. Salivarygland aplasia can be diagnosed with a large variety of imaging techniques, which include computer tomography(CT), magnetic resonance imaging (MR), ultrasonography (US), sialography, or scintigraphy. In this paper wereport a case of a patient referred to our department with a long term and progressive growing neck mass, who hasan unilateral submandibular gland aplasia associated to an ipsilateral hypertrophy of the sublingual gland (AU)

Prevalencia de la mutación A1555G del gen MTRNR1 en pacientes con hipoacusia postlocutiva sin antecedentes familiares de sordera / Prevalence of the A1555G MTDNA mutation in sporadic hearing-impaired patients without known history of aminoglycoside treatment

Introducción: La mutación A1555G del gen MTRNR1 del ADN mitocondrial es responsable de hipoacusia neurosensorial bilateral no sindrómica que se ve exacerbada por la exposición a aminoglucósidos. El objetivo de nuestro estudio fue determinar la frecuencia de esa mutación en pacientes con hipoacusia neurosensorial, postlocutiva, sin antecedentes familiares de hipoacusia, ni exposición a ototóxicos. Métodos: Se realizó una estudio genético para detectar la mutación A1555G del ADN mitocondrial en los pacientes que consultaron por hipoacusia neurosensorial bilateral postlocutiva, de etiología desconocida, en la consulta de ORL de un hospital comarcal durante 4 años. Resultados: Doscientos diecinueve pacientes fueron estudiados durante dicho período. Dos de ellos (0,9%) eran portadores de la mutación A1555G del ADN mitocondrial en homoplasmia. Ambos tenían una hipoacusia neurosensorial, bilateral y simétrica, moderada para frecuencias medias y severa para altas frecuencias no relacionada con la exposición a ototóxicos. Conclusiones: La mutación A1555G del gen MTDNR1 en pacientes con hipoacusia neurosensorial bilateral postlocutiva en ausencia de antecedentes familiares de hipoacusia por vía materna o desencadenada por aminoglucósidos, es poco frecuente en nuestro medio. Se debe sospechar en aquellos con hipoacusia neurosensorial bilateral con predominio para altas frecuencias menores de 50 años de edad (AU)

Introduction: The A1555G mitochondrial DNA (mtDNA) mutation is responsible for maternally inherited non-syndromic hearing loss that is increased by aminoglycoside exposure. The objective of this study was to ascertain the frequency of the A1555G mutation among patients without family history of hearing loss or known exposition to aminoglycosides. Methods: We screened for the mtDNA A1555G mutation in Spanish patients with sporadic sensorineural hearing impairment without a known family history of hearing loss or aminoglycoside exposition seen at the ENT Department in Sierrallana Hospital (Torrelavega, Cantabria, Spain) over a four-year period. Results: A total of 219 patients with bilateral hearing loss were screened. Two of them (0.9%) had the A1555G mitochondrial DNA mutation. Both patients had a moderate bilateral sensorineural hearing loss for low frequency, and moderate to severe loss for high-frequency. Conclusions: The mtDNA A1555G mutation in patients with sensorineural hearing loss without family history of deafness or aminoglycoside ototoxicity is infrequent in our region. We should suspect this mutation in patients younger than 50 years old, with postlingual bilateral sensorineural hearing loss that is more pronounced at high frequency (AU)

Predisposición familiar a la ototoxicidad de los aminoglucósidos debido a la mutación A1555G del ADN mitocondrial / Familial susceptibility to aminoglycoside ototoxicity due to the A1555G mutation in the mitochondrial DNA

FUNDAMENTO Y OBJETIVO: La mutación A1555G del genoma mitocondrial causa hipoacusia neurosensorial y ototoxicidad familiar por aminoglucósidos. PACIENTES Y MÉTODO: Se estudió la mutación A1555G en 72 pacientes con hipoacusia neurosensorial. RESULTADOS: Quince pacientes (20,8 por ciento) eran portadores de la mutación A1555G. Todos ellos presentaban antecedentes familiares de sordera por vía materna, y la hipoacusia era mayor si habían sido tratados con aminoglucósidos. CONCLUSIONES: Debe descartarse la presencia de la mutación A1555G en pacientes con antecedentes de hipoacusia por vía materna antes de administrar aminoglucósidos. (AU)