Estimated number of loci for autosomal recessive severe nerve deafness within the Israeli Jewish population, with implications for genetic counseling.

Deafness occurs in about 1 per thousand live births, and at least 50% of congenital deafness is hereditary. The aim of this study was to examine the number of loci for recessively inherited severe nerve deafness of early onset within the Israeli population and to compare the results to those obtained in other populations. The Jewish population in Israel originates from many countries and may be divided into Sephardi, Eastern and Ashkenazi Jews, and the matings will be intraethnic or interethnic. Data were obtained on 133 deaf couples who lived in the Tel Aviv area, through the files of the Helen Keller Center. Causes of deafness in the spouses were studied and data on their children were obtained. Among 111 couples who had recessive or possibly recessive deafness and had at least 1 child, there were 12 with only deaf children and 5 with both deaf and hearing children. The number of loci for recessive deafness in the whole group was estimated at 8-9. Intraethnic and interethnic matings gave an estimate of 6.7 and 22.0 loci, respectively, which indicates that within populations fewer loci exist with recessive mutations for deafness than between populations. It could be shown that the sharing of loci between spouses decreased with increasing geographical distance of their origin. The results provide data for genetic counseling in Israel for deaf couples who have no children or have one hearing or one deaf child.