USHER-SYNDROME IN THE CITY OF BIRMINGHAM - PREVALENCE AND CLINICAL CLASSIFICATION

Aims-To estimate the prevalence of Usher syndrome in the city of Birmi ngham, and to establish a database of patients who have been classifie d 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 exami nation of medical records and patient questionnaires allowed classific ation of three subtypes, US 1, US 2, and US 3. In addition, family ped igrees were examined and blood was taken from index patients for DNA e xtraction. Results-In the population aged over 15 years the prevalence was 6.2 per 100000 population for all US subtypes. The prevalence for US 1 and US 2 was 5.3 per 100000 population. This is greater than pre viously reported. In the age group 30-49 years the prevalence approach ed 1 in 10000. Clinical classification found 33% US 1, 47% US 2, and 2 0% US 3. Conclusion-This higher prevalence rate and greater frequency of US 2 and US 3 may reflect a more complete ascertainment.