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We report an infant with auditory neuropathy secondary to the Q829X mutation in the gene encoding otoferlin (OTOF). Included in a universal newborn hearing screening program, the subject passed the otoacoustic emission (OAEs) test. Given that the infant had a familial history of deafness auditory brainstem response (ABR) testing was performed, revealing a profound hearing impairment. The genetic study confirmed that the subject was homozygous for the Q829X mutation in OTOF. The patient underwent a cochlear implant, obtaining satisfactory results. The moderately high prevalence of this mutation in the Spanish population could produce a significant false negative rate in newborn hearing screening programs using OAEs.

Introduction: The most frequent mutations responsible for non-syndromic hearing impairment in the Spanish population are the 35delG mutation in the connexin 26 gene (GJB2), the del(GJB6-D13S1830) deletion in the connexin 30 gene (GJB6), the Q829X mutation in the otoferlin gene (OTOF), and the A1555G mutation in the 12S rRNA gene of the mitochondrial genome., Patients and Methods: Screening for these mutations was performed on 38 patients from Cantabria with non-syndromic sensorineural hearing impairment of congenital/childhood onset., Results: The A1555G mutation was detected in homoplasmy in 9 patients (23.7%). Three individuals were heterozygous for the 35delG mutation (7.9%). The heterozygous del(GJB6-D13S1830) deletion was present in one case (2.6%). One subject was homozygous for the Q829X mutation (2.6%)., Conclusions: These four mutations are present in 36.8% of all cases of non-syndromic hearing impairment in our population.

Objective: To determine the features of hearing loss due to the Q829X mutation in the OTOF gene, the third most frequent mutation causing prelingual deafness reported so far in the Spanish population., Materials and Methods: We carried out genetic characterisation of 16 individuals from a consanguineous family from Cantabria, in which 4 members were affected by deafness., Results: All 4 hearing impaired individuals were homozygous for the Q829X mutation in the OTOF gene. The auditory defect was a profound, bilateral, symmetrical, sensorineural hearing loss of prelingual onset. No other clinical alterations were observed. Individuals heterozygous for the Q829X mutation were unaffected., Conclusions: The Q829X mutation in the OTOF gene causes severe to profound sensorineural hearing loss of prelingual onset. Early detection of individuals carrying this mutation is important for the application of palliative treatment and special education.

Objective: To examine the audiometric patterns of familial hearing impairment due to the A1555G mutation in the mitochondrial DNA., Patients and Methods: We include 55 subjects with the A1555G mutation from 6 unrelated families, affected by nonsyndromic sensorineural hearing loss and residing in Cantabria. The A1555G mutation was found in homoplasmy in all the families, except in one family, in which it was in heteroplasmy. Aside from standard history taking and general otolaryngological examination, pure tone audiometry was carried out in all patients., Results: Hearing loss was developed by most of the patients. The auditory defect was a slowly progressive bilateral symmetrical sensorineural hearing loss, affecting mainly the high frequencies. In patients in which aminoglycoside ototoxicity could be excluded, hearing loss usually ranged from mild to moderate, with a late onset. In 17 cases there were previous history of treatment with a ototoxic drugs, and most of them developed severe hearing loss. One of them was deaf-mute. No audometric differences between families with the homoplasmic and the heteroplasmic A1555G mutation were observed., Conclusions: Patients with the A1555G mutation generally present bilateral symmetrical sensorineural hearing loss, ranging from mild to moderate, slowly progressive, which is obvious approximately in the second decade of life and affects specially the high frequencies. Hearing loss severity is increased by treatment with aminoglycosides.

Introduction: Sensorineural deafness is a very common disorder in humans, which affects approximately 10% of the population. Genetic causes are suggested to be responsible for more than half of the cases. The A1555G mutation in the mitochondrial 12S rRNA gene and the 35delG mutation in the GJB2 gene are the most common mutations for sensorineural deafness in the Spanish population., Methods: A genetic study was carried out in order to determine the frequency of the mutations A1555G in the mitochondrial DNA and 35delG in the connexin-26 gene in 21 patients from 21 non-consanguineous unrelated families affected by late-onset bilateral non-syndromic sensorineural hearing loss from Cantabria., Results: The A1555G mutation was found in 6 patients. Five of these 6 patients had been treated with aminoglycosides. In all of them the auditory impairment affected mainly the high frequencies. The 35delG mutation was not found in any of the patients., Conclusions: The A1555G mutation in the mitochondrial DNA has been found to be the most common amongst the Cantabrian population. The A1555G mutation should be suspected in those members of families affected by sensorineural hearing impairment with a maternal inheritance pattern and ototoxicity from treatment with aminoglycoside antibiotics. The 35delG mutation in the GJB2 gene does not seem to be a major cause of deafness in families with late-onset non-syndromic sensorineural hearing loss in our area.