To identify the genes causing recessive hearing loss in Saudi population. Duration: 3 years
 Several hundred genes are known to cause hereditary hearing loss and deafness.  The hearing loss may be conductive, sensorineural, or mixed; syndromic or nonsyndromic; and prelingual (before language develops) or postlingual (after language develops).   Genetic forms of hearing loss must be carefully distinguished from acquired (non-genetic) causes of hearing loss.  The genetic forms of hearing loss are diagnosed by clinical examination, audiology, family history, ancillary testing (such as CT examination of the temporal bone), and DNA-based testing.  DNA-based genetic tests are available for many types of syndromic and non-syndromic deafness, although usually only on a research basis, are poorly understood and only rarely applied in the Saudi population.  As hereditary hearing loss can be inherited in several well recognized genetic patterns, genetic counseling and risk assessment depends on accurate determination of the specific genetic diagnosis.  In the Saudi population, this is heavily dependent upon research to confirm underlying defects and patterns of inheritance.  As with other hereditary diseases such as cystic fibrosis, it is highly likely that unique genetic defects will be identified in the Saudi population.  Until the genetic basis of hereditary deafness in the Saudi population is well understood, the application of genetic testing for diagnosis, prevention and eventually therapeutic strategies in deafness in this community will be severely limited. Characteristically, within the Saudi population, families are large and the incidences of consanguineous marriages are common. These two characteristics underlie the availability of many families in which there are multiple affected individuals with hereditary diseases such as deafness.  A collection of some 200 families in which hereditary deafness is apparent will provide the basis from which the genetic defects underlying deafness in this population can be identified.  In addition, the identification of the most common forms of hereditary deafness and their incidence and distribution in the Saudi population will result from this study.  The application of this knowledge to newborn and pre-marital screening will have a major impact upon early intervention for and prevention of hereditary deafness.

Dr. Faiqa Imtiaz, PhD; Dr. Mohammad Al-Owain

Up to January 2007, 738 patients/family members have been enrolled in the project. Of the 738 patients enrolled, blood samples have been received and DNA banked for over 538 patients. Previous analysis excluded DFNB1 as a major cause of hereditary non-syndromic deafness in Saudi Arabia. Further results of linkage analysis identified the DFNB3 locus which harbors the MYO15A and the MYO18A genes (both identified to be promising candidates for causing non-syndromic deafness in Saudi Arabia). The project was completed on 28 February 2007.

King Faisal Specialist Hospital & Research Center

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