INITIAL EXPERIENCE WITH THE IDENTIFICATION OF FAMILIES WITH HEREDITARY HEARING-LOSS IN TURKEY

The authors describe a study in progress to identify Turkish families with hereditary hearing loss and isolate possible responsible disease genes. Due to extreme genetic heterogeneity and limited audiological d ifferentiation of hereditary hearing loss, it is necessary to identify large or small families from genetic isolates to locate loci responsi ble for hearing loss on a chromosome. To accomplish this goal, the med ical records of 3800 children were examined at the ENT Clinic of Ege U niversity between 1975 and 1994. All were suspected of having various hearing impairments. Additional ly, students from two schools for the hearing impaired in Izmir and Eskisehir, Turkey were examined. To date , 16 families with syndromal deafness and 55 families with non-syndrom al hereditary hearing loss involving two or more affected individuals have been identified and categorized according to the mode of inherita nce. The majority (66%) of the non-syndromal families showed an autoso mal recessive pattern, 29% an autosomal dominant inheritance and 5% an X-Iinked mode of inheritance. In the study presented there has been a predominance of affected males versus females and the consanguinity r ate was 22%.