Phenotype description of a Dutch otosclerosis family with suggestive linkage to OTSC7.

This study reports on a clinical investigation of a Dutch family that shows suggestive linkage to OTSC7. Cross-sectional as well as longitudinal analyses of audiometric data were performed. Also, high-resolution computed tomography (CT) images of the temporal bones from genetically affected family members were obtained to study the incidence and extent of otospongiotic foci. Audiometric data showed a considerable degree of phenotypic variability. Cross-sectional regression analysis did not show age-dependent progression of bone conduction (BC), air conduction (AC), and air-bone gap (ABG) levels. Longitudinal analysis of audiometric follow-up data of one family member showed age-dependent progression of AC, BC, and ABG levels. High-resolution CT images revealed an otospongiotic focus in six of six (100%) clinically affected individuals that carried the disease haplotype. In none of the clinically unaffected family members that showed linkage to OTSC7, an otospongiotic focus was detected by CT. In conclusion, hearing impairment in the present otosclerosis family seems to be variable in terms of onset age and level of progression. Long-term audiometric data of one patient proved to be valuable in understanding progression of hearing impairment in this individual. The detection rate of otospongiotic foci in our study group is similar compared to previous reports on CT data in consecutive otosclerosis patients who had stapes replacing surgery.