Clinical and genetic linkage analysis of a large Venezuelan kindred with Usher syndrome.

OBJECTIVE: To undertake a comprehensive investigation into the very high incidence of congenital deafness on the Macano peninsula of Margarita Island, Venezuela. METHODS: Numerous visits were made to the isolated island community over a 4-year-period. During these visits, it became apparent that a significant number of individuals complained of problems with hearing and vision. Socioeconomic assessments, family pedigrees and clinical histories were recorded on standard questionnaires. All individuals underwent thorough otolaryngologic and ophthalmologic examinations. Twenty milliliters of peripheral venous blood was obtained from each participant. A genome-wide linkage analysis study was performed. Polymorphic microsatellite markers were amplified by polymerase chain reaction and separated on polyacrylamide gels. An ABI 377XL sequencer was used to separate fragments and LOD scores were calculated by using published software. RESULTS: Twenty-four families were identified, comprising 329 individuals, age range 1-80 years, including 184 children. All families were categorized in the lower two (least affluent) socioeconomic categories. A high incidence of consanguinity was detected. Fifteen individuals (11 adults, 4 children) had profound congenital sensorineural hearing loss, vestibular areflexia and retinitis pigmentosa. A maximum LOD score of 6.76 (Linkage >3.0), between markers D11s4186 and D11s911, confirmed linkage to chromosome 11q13.5. The gene myosin VIIA (MYO7A) was confirmed in the interval. Clinical and genetic findings are consistent with a diagnosis of Usher syndrome 1B for those with hearing and vision problems. CONCLUSIONS: We report 15 Usher syndrome 1B individuals from a newly detected Latin American socio-demographic origin, with a very high prevalence of 76 per 100,000 population.

Prevalence and impact of chronic otitis media in school age children in Brazil. First epidemiologic study concerning chronic otitis media in Latin America.

OBJECTIVE: The first epidemiological study carried out in Latin America to investigate the prevalence of otological disease and its impact in a representative random sample of the school children population. METHODS: A cross sectional epidemiological survey to investigate the epidemiology of otitis in a representative random sample of 1119 children and adolescents from a total of 486166 elementary and high-school students, aged 6-18 years, regularly registered in one of the 521 public and private schools of the city of Belo Horizonte, in the state of Minas Gerais, southern Brazil. The interviews were conducted individually, in the school, by an otolaryngologist or a pediatrician. The interview included all of the personal data and also detailed questions regarding otological disorders and hearing. The otological examination was carried out with Mini-Heine otoscopes and the audiometric evaluation with the AudioScope 3 with 25dB intensity. The questionnaire and basic procedures for medical examination had been previously tested through a pilot test in two schools. RESULTS: The prevalence of chronic otitis media was 0.94%. Impacted wax was found in 12.3% of the students. The prevalence of abnormalities (excluding wax) in the otoscopy examination was 10.5%. It was found that 8.3% of students had a past history of otitis and 7.7% had a past history of otorrhea. These two special groups presented statistically significant associations with chronic otitis media, hearing loss and otolaryngological surgeries (when compared with the other school children). Parents and school children seemed significantly able to identify a special group of children with past history of otitis during childhood.