title: Usher syndrome in the city of Birmingham--prevalence and clinical classification.
abstract: OBJECTIVE
  To estimate the prevalence of Usher syndrome in the city of Birmingham, and to establish a database of patients who have been classified into different clinical subtypes essential for future gene mutation analysis.
  
  
  METHODS
  Symptomatic cases of Usher syndrome (US) resident in the city of Birmingham in June 1994 were ascertained through multiple sources. Ophthalmic and audiological reassessment together with examination of medical records and patient questionnaires allowed classification of three subtypes, US 1, US 2, and US 3. In addition, family pedigrees were examined and blood was taken from index patients for DNA extraction.
  
  
  RESULTS
  In the population aged over 15 years the prevalence was 6.2 per 100 000 population for all US subtypes. The prevalence for US 1 and US 2 was 5.3 per 100 000 population. This is greater than previously reported. In the age group 30-49 years the prevalence approached 1 in 10 000. Clinical classification found 33% US 1, 47% US 2, and 20% US 3.
  
  
  CONCLUSIONS
  This higher prevalence rate and greater frequency of US 2 and US 3 may reflect a more complete ascertainment.
authors.affiliation: Department of Ophthalmology, University of Birmingham.
authors.forename: C I
authors.initials: CI
authors.lastname: Hope
authors.forename: S
authors.initials: S
authors.lastname: Bundey
authors.forename: D
authors.initials: D
authors.lastname: Proops
authors.forename: A R
authors.initials: AR
authors.lastname: Fielder
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003638:Deafness / Q000150:complications / Q000453:epidemiology* / Q000235:genetics; D004739:England / Q000453:epidemiology; D005260:Female; D005808:Genes, Recessive; D006320:Hearing Tests; D006801:Humans; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D015995:Prevalence; D012174:Retinitis Pigmentosa / Q000150:complications / Q000453:epidemiology* / Q000235:genetics; D013577:Syndrome; D015837:Vestibular Diseases / Q000150:complications / Q000453:epidemiology / Q000235:genetics; D014724:Vestibular Function Tests; D014787:Vision Tests