To perform genetic analysis and to analyze cochleovestibular impairment features in a newly identified Dutch family with nonsyndromic autosomal dominant hearing impairment (DFNA9).
Genetic analysis was performed using microsatellite markers and single nucleotide polymorphisms. Audiometric data were collected and analyzed longitudinally. Results were compared with those obtained in previously identified P51S COCH mutation carriers (n = 74). Special attention was also given to a comparison of age-related features such as progressive hearing loss and vestibular impairment.
Tertiary referral center.
G88E COCH mutation carriers from a Dutch family.
The study of clinical features of a DFNA9 family carrying a G88E COCH mutation and to compare this to the symptoms of those carrying a P51S/COCH mutation.
Pure-tone thresholds, phoneme recognition scores, and vestibular responses of the G88E mutation carriers were essentially similar to those previously established in the P51S mutation carriers. Hearing started to deteriorate in G88E mutation carriers from age 46 to 49 years and onward, whereas deterioration of vestibular function started from approximately age 46 years. In the P51S mutation carriers, vestibular impairment started earlier, at approximately age 34 years. However, the difference in age of onset with the G88E mutation carriers was not significant. Remarkably, the proportion of patients who developed complete vestibular areflexia within the age range of 40 to 56 years was significantly lower for the G88E mutation carriers than for the P51S mutation carriers.
Apart from a significantly lower frequency of vestibular areflexia between the ages of 40 and 56 years, there are no phenotypic differences between carriers of the G88E and P51S mutations in the COCH gene.
Departments of *Otorhinolaryngology and †Human Genetics, Radboud University Medical Center Nijmegen, Nijmegen, The Netherlands; ‡Department of Otorhinolaryngology-Head and Neck Surgery, University Hospital Ghent, Ghent, Belgium; and Departments of §Pathology and ∥Obstetrics, Gynecology and Reproductive Biology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A.
Address correspondence and reprint requests to M. H. Kemperman, Ph.D., Department of Otorhinolaryngology, Radboud University Medical Center Nijmegen, P. O. Box 9101, 6500 HB Nijmegen, The Netherlands; E-mail: M.Kemperman@kno.umcn.nl
Supported by the Dutch Organization for Scientific Research, Counsel for Medical and Health Research (project 920-03-100), the Heinsius Houbolt Foundation, the Nijmegen Otorhinolaryngology Foundation, and the National Institutes of Health (grant DC03402).