Autosomal recessive non-syndromic hearing loss in the Lebanese population: prevalence of the 30delG mutation and report of two novel mutations in the connexin 26 (GJB2) gene.

EDITOR—The most common sensory deficit in humans is hearing loss, aVecting 1 in 1000 children, with approximately half of the cases having a genetic cause. The majority of these genetic causes are non-syndromic, of which approximately 75% have an autosomal recessive mode of inheritance. So far, nearly 30 genes that cause non-syndromic recessive deafness (NSRD) have been located (for review see http://dnalab-www.uia.ac.be/ dnalab/hhh). The loci corresponding to NSRD are designated DFNB, with a number corresponding to the chronology of their localisation. The first locus, DFNB1 (MIM 220290), located on chromosome 13q11-12, has been shown to be responsible for nearly half of NSRD owing to mutations in the gene encoding the gap junction protein connexin 26 (GJB2) (MIM 121011). 4 One mutation, 30delG (also referred to as 35delG), accounts for the majority of mutations in this gene in some ethnic groups, while it is rarer in others. The geographical position of Lebanon, a small country of 10 500 km on the eastern shores of the Mediterranean sea, has made it a historical crossroads between Asia, Africa, and Europe. As a consequence, the Lebanese population shows a wide genetic diversity, with no less than 17 ethno-religious communities. Today, the population is approximately 4 million people, with a world wide diaspora estimated at 15 million. In Lebanon, consanguineous marriages are still frequent (from 10 to 30%), favouring the incidence of autosomal recessive diseases, such as haemoglobinopathies, sickle cell anaemia, familial Mediterranean fever, congenital hypothyroidism, cystic fibrosis, and deafness. The purpose of this study is to summarise the diVerent NSRD loci found in a case series of Lebanese families and to determine the carrier frequency of the 30delG mutation in selected Lebanese subjects.