Deafness has a very variable disease. It may occur as a result of external auditory canal involvement or a de ciency in the sound conduction mechanism (transmission deafness) or impairment of the cochlear, cochlear nerve or central auditory perception. Genetics is the most common cause, as approximately 70% of hearing disorders are of hereditary origin. 1/3 of hereditary deafness is syndromic (associated with other symptoms) and 2/3 are non-syndromic (isolated deafness). At this date, 173 loci of deafness gene have been reported in the literature (69 DFNA, 94 DFNB, 6 X-linked DFN, 2 DFNM, 1 DFNY and 1 AUNA1). For syndromic deafness, approximately 400 syndromes associated with hearing disorders are already described.Thus, the determination of causal mutations is a valuable aid for accurate and early diagnosis. This makes it possible to better guide the management since forms of deafness respond better to the cochlear implant than others. The correct diagnosis also gives an idea of the evolutionary pro le of deafness and whether it is a syndromic deafness requiring special surveillance. In this study, we have examined the genetic causes of sensorineural hearing loss in Moroccan patients through whole exome sequencing (WES) to identify candidate genes for six severely deaf Moroccan families. The results revealed four genetic variants in the genes GJB2, COL4A3, ATP6V1B1 and EDNRB, which are therefore common causes of syndromic and non-syndromic deafness.

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