Molecular genetic aspects of hereditary hearing impairment

Hereditary hearing impairment (HI) is a clinically and genetically heterogeneous entity, which assumedly present at least one third of all hearing impairment in humans. The incidence of severe to profound hearing loss in newborns is 1-2 in 1000 live births. At least 50% of these cases can be attributed to genetic causes. Depending on the clinical appearance, syndromic and non-syndromic hereditary hearing impairment can be distinguished. Up to 33% of all hereditary hearing impairment is syndromic. This entity includes 1168 syndromes with otologic manifestations. The remaining 67% represents non-syndromic hearing impairment with no additional clinical features besides HI. Non-syndromic HI is further classified by the mode of inheritance in autosomal-dominant (18%), autosomal-recessive (80%), X-linked (1-2%) and mitochondrial (<1%) hearing impairment.
Identification of the molecular background of hearing loss is a first step to understand mechanisms which form the knowledge basis for a causal treatment of the loss of hearing based on new technologies such as gene therapy or cell regeneration
The authors present a brief overview on current status on gene identification, the diagnostic considerations when evaluating a patient who might have a hereditary hearing impairment as well as briefly describe treatment options based on gene therapy.