Abstract: Objective: To ascertain pathogenic variants frequency and type in the COCH gene among Cantabrian patients with nonsyndromic hereditary hearing loss (HL), and to understand their cochleovestibular manifestations. Study design: An observational study on patients with postlingual nonsyndromic sensorineural hearing loss (SNHL), who underwent a genetic study using next-generation sequencing (gene panel) in the otolaryngology clinics between January 2019 and December 2023. Setting: Referral center Marqués de Valdecilla University Hospital in Santander (Spain). Methods: A cohort of 248 otolaryngologic clinic-referred patients suspected of genetic SNHL underwent sequencing analysis targeting 231 genes. Results: A likely pathogenic or pathogenic variant causing HL was found in 57 (22.8%) patients. Among them, 7 (2.8%) were heterozygous carriers of the c.263G>C variant in the LCCL domain of the COCH gene, included as index cases. Subsequent familial segregation studies were performed. A total of 22 genetically and clinically studied patients were included. All but 3 family members displayed bilateral progressive SNHL starting in adulthood. Thirteen patients reported instability, but none met Meniere's disease criteria. Conclusion: COCH gene variants are frequent in Cantabria. A variant with pathogenic evidence (c.263G>C in the LCCL domain) was detected. The phenotype observed is similar to a subgroup of patients with other variants described in the same functional domain: progressive SNHL and instability secondary to vestibular hypofunction.

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