A Novel COCH Mutation Affects the vWFA2 Domain and Leads to a Relatively Mild DFNA9 Phenotype

Abstract

Objective: To study the genotype and phenotype of a Dutch family with autosomal dominantly inherited hearing loss.

Study design: Genotype-phenotype correlation study. Genetic analysis consisted of linkage analysis, variable number of tandem repeats analysis, and Sanger sequencing. Audiovestibular function was examined. Regression analysis was performed on pure tone audiometry and speech recognition scores and correlated with the age and/or level of hearing loss.

Setting: Tertiary referral center.

Patients: A large Dutch family presenting with sensorineural hearing loss.

Main outcome measures: Identification of the underlying genetic defect of the hearing loss in this family. Results of pure tone and speech audiometry, onset age, progression of hearing loss and vestibular (dys)function.

Results: A novel mutation in COCH, c.1312C > T p.(Arg438Cys), cosegregates with hearing loss and a variable degree of vestibular (dys)function in this family. The reported mean age of onset of hearing loss is 33 years (range, 18-49 yr). Hearing loss primarily affects higher frequencies and its progression is relatively mild (0.8 dB/yr). Speech perception is remarkably well preserved in affected family members when compared with other DFNA9 families with different COCH mutations.

Conclusion: These findings expand the genotypic and phenotypic spectrum of DFNA9. The c.1312C > T mutation, which affects the vWFA2 domain, causes a relatively mild audiovestibular phenotype when compared with other COCH mutations.