Introduction:
Mutations at the DFNA9 locus on chromosome 14q12 are the third most common form of DFNA hearing loss, which is clinically characterized by late onset (in adulthood) progressive sensorineural hearing loss accompanied by vestibular dysfunction. The aim of the study was to search for COCH gene mutations (P51S, V66G, G87W, G88E, V104del, I109N, W117R, A119T, M512T, C542Y) in patients with severe or profound sensorineural hearing loss accompanied by a vestibular lesion.

Material and methods:
The study was based on a group of 30 patients. Qualification criteria comprised the presence of progressive postlingual, severe to profound sensorineural hearing loss with tinnitus, early age of sensorineural hearing loss onset, before the 40th year of life, and a positive family history of early onset hearing loss. All patients were diagnosed with peripheral vestibular lesions.

Results:
The authors did not find P51S, V66G, G87W, G88E, V104del, I109N, W117R, A119T, M512T, or C542Y mutations in the COCH gene in the tested group (no differences were found in the nucleotide sequences of exomes 4, 5 and 12 when compared to the published cDNA sequence of the COCH gene).

Conclusions:
No cochlin mutations were found in the group of patients with severe to profound sensorineural hearing impairment accompanied by a vestibular lesion. The COCH gene needs further exploration and analysis of genotype-phenotype correlations.