By this an understanding of the related pathophysiology could be gained. These are still of considerable importance to explain some of the relevant differences in phenotypes based on different genotypes. This does not disqualify clinical studies on the Usher syndromes. Whereas in the past clinical examination was needed for diagnosing the subtypes of Usher syndrome, such a diagnosis, at present, will be based mainly on either linkage analysis or mutation analysis. Mutations in this gene seem to cause USH2A. 14 Recently, Eudy et al 15 reported on a gene encoding a protein with extracellular matrix motifs. In 1995, mutations in the human myosin VIIa gene were found to be responsible for USH1B. 13 In the Netherlands and Belgium, USH1B and USH2A are most frequently encountered. 6 - 12 Usher syndrome type III has been linked to only 1 locus so far (USH3) and is mainly diagnosed in Finland. Usher syndrome type I consists of 6 genetic subtypes (USH1A through F), whereas Usher syndrome type II has 2 genetic subtypes (USH2A and B). Since 1990, linkage studies by several groups have demonstrated extensive genetic heterogeneity within Usher syndrome. 5Īs early as 1959, Hallgren 4 suggested that the different clinical subtypes were related to different genetic subtypes. Three clinical types, Usher types I, II, and III, were distinguished, which was important for counseling purposes and gene linkage studies. Extensive clinical studies have been performed to outline the clinical heterogeneity. 3 Later, Hallgren 4 pointed out that at least 2 distinct clinical types existed. von Wibout 2 suggested that the syndrome had an autosomal recessive mode of inheritance.Ĭlinical heterogeneity within the syndrome was first described by Bell. 1 Several authors emphasized a high prevalence of this syndrome in certain families, and a hereditary nature was suspected. THE USHER syndrome was first described in 1858 and characterized as a disorder with bilateral sensorineural hearing loss and visual impairment caused by tapetoretinal degeneration. Hearing impairment in our patients with USH2A could be characterized as progressive. Progression of hearing impairment in USH2A was 0.7 dB/y on average for 0.25 to 4 kHz and could not be explained by presbyacusis alone.Ĭonclusions The USH1B and USH2A can be easily distinguished by hearing impairment at younger than 40 years at the low frequencies. Distinctive audiographic features of patients with USH2A were maximum hearing thresholds of 70, 80, and 100 dB at 0.25, 0.5, and 1 kHz, respectively, only at younger than 40 years. Mean thresholds of patients with USH2A were about 45 to 55 dB better than these minimum values. Results The patients with USH1B had residual hearing without age dependence, with minimum thresholds of 80, 95, and 120 dB at 0.25, 0.5, and 1 to 2 kHz, respectively. Main Outcome Measure Pure tone audiometry of the best ear at last visit. All participants were living in the Netherlands and Belgium. Patients Nineteen patients with USH1B and 27 with USH2A were examined. Setting Otolaryngology department, university referral center. Objective To evaluate hearing impairment in 2 common genetic subtypes of Usher syndrome, USH1B and USH2A.ĭesign Cross-sectional analysis of hearing threshold related to age in patients with genotypes determined by linkage and mutation analysis. Shared Decision Making and Communication.Scientific Discovery and the Future of Medicine.Health Care Economics, Insurance, Payment.Clinical Implications of Basic Neuroscience.Challenges in Clinical Electrocardiography.
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