A combination of two truncating mutations in USH2A causes more severe and progressive hearing impairment in Usher syndrome type IIa.

OBJECTIVES: Usher syndrome is an inherited disorder that is characterized by hearing impairment (HI), retinitis pigmentosa, and in some cases vestibular dysfunction. Usher syndrome type IIa is caused by mutations in USH2A. HI in these patients is highly heterogeneous and the present study evaluates the effects of different types of USH2A mutations on the audiometric phenotype. Data from two large centres of expertise on Usher Syndrome in the Netherlands and Sweden were combined in order to create a large combined sample of patients to identify possible genotype-phenotype correlations. DESIGN: A retrospective study on HI in 110 patients (65 Dutch and 45 Swedish) genetically diagnosed with Usher syndrome type IIa. We used methods especially designed for characterizing and testing differences in audiological phenotype between patient subgroups. These methods included Age Related Typical Audiograms (ARTA) and a method to evaluate the difference in the degree of HI developed throughout life between subgroups. RESULTS: Cross-sectional linear regression analysis of last-visit audiograms for the best hearing ear demonstrated a gradual decline of hearing over decades. The congenital level of HI was in the range of 16-33 dB at 0.25-0.5 kHz, and in the range of 51-60 dB at 1-8 kHz. The annual threshold deterioration was in the range of 0.4-0.5 dB/year at 0.25-2 kHz and in the range of 0.7-0.8 dB/year at 4-8 kHz. Patients with two truncating mutations, including homozygotes for the common c.2299delG mutation, developed significantly more severe HI throughout life than patients with one truncating mutation combined with one nontruncating mutation, and patients with two nontruncating mutations. CONCLUSIONS: The results have direct implications for patient counselling in terms of prognosis of hearing and may serve as baseline measures for future (genetic) therapeutic interventions.

Expressivity of hearing loss in cases with Usher syndrome type IIA.

OBJECTIVE: The purpose of this study was to compare the genotype/phenotype relationship between siblings with identical USH2A pathologic mutations and the consequent audiologic phenotypes, in particular degree of hearing loss (HL). Decade audiograms were also compared among two groups of affected subjects with different mutations of USH2A. DESIGN: DNA samples from patients with Usher syndrome type II were analysed. The audiological features of patients and affected siblings with USH2A mutations were also examined to identify genotype-phenotype correlations. STUDY SAMPLE: Genetic and audiometric examinations were performed in 18 subjects from nine families with Usher syndrome type IIA. RESULTS: Three different USH2A mutations were identified in the affected subjects. Both similarities and differences of the auditory phenotype were seen in families with several affected siblings. A variable degree of hearing loss, ranging from mild to profound, was observed among affected subjects. No significant differences in hearing thresholds were found the group of affected subjects with different pathological mutations. CONCLUSIONS: Our results indicate that mutations in the USH2A gene and the resulting phenotype are probably modulated by other variables, such as modifying genes, epigenetics or environmental factors which may be of importance for better understanding the etiology of Usher syndrome.

Long-term ophthalmic health care in Usher syndrome type I from an ICF perspective.

PURPOSE: The aim was to explore ophthalmic health care in female patients with Usher Syndrome type I (USH I) over 20 years and to evaluate the relationship between the ophthalmic health care and the health state of the patients from a health perspective. METHODS: A retrospective study of records from ophthalmology departments (OD) and low vision clinics (LVC) from 1985 to 2004. Assessment of the reports was performed based on the International Classification of Functioning, Disability and Health (ICF). Findings were analysed by manifest content analysis with ICF as a framework and using four themes: health care system, procedure examinations, patient's functioning and disability and procedure actions. RESULTS: The records of nine female patients (aged 25-39 years, 1985) with USH I were selected from the national database of USH. A great number of notes were collected (OD 344 and LVC 566). Procedure examinations were exclusively oriented towards body structure and function. All patients showed aggravated visual impairment over and above the hearing and vestibular impairment. Procedure actions were oriented towards environmental factors. No correlation was found between procedures performed and patient's experience of disability. CONCLUSIONS: The high degree of resource allocation was not correlated to the patients' impairment. The study indicates that the ophthalmic health care was characterised by inefficiency. This conclusion is very serious because patients very likely face severe disability and emotional difficulties. ICF is ought to be incorporated in ophthalmic health care strategy to improve the health care.

Spectrum of USH2A mutations in Scandinavian patients with Usher syndrome type II.

Usher syndrome type II (USH2) is an autosomal recessive disorder, characterised by moderate to severe high-frequency hearing impairment, normal balance function and progressive visual impairment due to retinitis pigmentosa. Usher syndrome type IIa, the most common subtype, is defined by mutations in the USH2A gene encoding a short and a recently discovered long usherin isoform comprising 21 and 73 exons, respectively. More than 120 different disease-causing mutations have been reported, however, most of the previous reports concern mutations restricted to exons 1-21 of the USH2A gene. To explore the spectrum of USH2A disease-causing mutations among Scandinavian USH2 cases, patients from 118 unrelated families of which 27 previously had been found to carry mutations in exons 1-21 were subjected to extensive DNA sequence analysis of the full size USH2A gene. Altogether, 122 USH2A DNA sequence alterations were identified of which 57 were predicted to be disease-causing, 7 were considered to be of uncertain pathogenicity and 58 were predicted to be benign variants. Of 36 novel pathogenic USH2A mutations 31 were located in exons 22-73, specific to the long isoform. USH2A mutations were identified in 89/118 (75.4%) families. In 79/89 (88.8%) of these families two pathogenic mutations were identified whereas in 10/89 (11.2%) families the second mutation remained unidentified. In 5/118 (4.2%) families the USH phenotype could be explained by mutations in the USH3A gene. The results presented here provide a comprehensive picture of the genetic aetiology of Usher syndrome type IIA in Scandinavia as it is known to date.

Longterm visual prognosis in Usher syndrome types 1 and 2.

PURPOSE: To estimate the age at diagnosis of retinitis pigmentosa and to determine visual acuity deterioration, visual field impairment and the frequency of cataracts in Usher syndrome types 1 and 2. METHODS: We carried out a retrospective study of 328 affected subjects with Usher syndrome types 1 and 2. Study subjects were divided into seven different age groups by decade. Data were analysed using descriptive statistics, general linear model anova and survival analysis. RESULTS: Retinitis pigmentosa was diagnosed significantly earlier in subjects with Usher syndrome type 1 than in those with type 2. Visual acuity was significantly more impaired in affected subjects with Usher syndrome type 1 than in those with type 2 from 50 years of age onwards. Survival analysis revealed a significant difference in visual field loss (