A Dutch family with hearing loss linked to the DFNA20/26 locus: longitudinal analysis of hearing impairment.

Objectives: To perform linkage analysis and to outline hearing loss characteristics in a family exhibiting a nonsyndromic, autosomal dominant type of progressive sensorineural hearing loss.

Design: Genetic analysis was performed using microsatellite markers. Audiometric data were collected and analyzed longitudinally. Sigmoidal dose-response curves enabled us to perform nonlinear regression analysis per frequency and on phoneme recognition scores. Speech recognition scores were compared with those of DFNA2, DFNA5, DFNA9, and presbyacusis subjects.

Subjects: Affected family members of a Dutch family (W99-060).

Results: We revealed linkage of hearing loss to the DFNA20/26 locus (maximum logarithm of odds score, 3.1 at theta=0.04) and reduced the critical region from 12 to 9.5 centimorgans. Patients younger than 15 years already showed gently downsloping audiograms. At ages 15 to 20 and 25 to 40 years, hearing loss was profound at 8 kHz and 1 to 4 kHz, respectively. The 0.25- to 0.5-kHz thresholds showed more gradual progression by about 1.5 to 2 dB/y. From about age 40 years onward, hearing was residual. Hearing impairment took a more severe course than in a known DFNA20 family. Score recognition in DFNA20/26 subjects was better than in DFNA9 subjects at any pure-tone average (1-4 kHz) threshold. Compared with subjects having DFNA2 and DFNA5, speech recognition in those with DFNA20/26 scored better at threshold levels below 85 dB hearing level, but worse at levels above 90 dB. Compared with presbyacusis subjects, those with DFNA20/26 scored better in speech recognition at levels below 100 dB and worse at levels above 100 dB.

Conclusions: Autosomal dominant hearing loss is linked to the DFNA20/26 locus in this Dutch family. The critical region is reduced from 12 to 9.5 centimorgans. Phenotypically, patients are more severely affected than those of a known DFNA20 family.