Abstract
The identification of genes leading to hereditary hearing impairment is one of the ways to elucidate the functioning of the inner ear. Over the past few years, several genes responsible for non-syndromal hereditary hearing impairment have been identified. One of these genes, named COCH, is responsible for autosomal dominant progressive sensorineural hearing loss associated with vestibular impairment (DFNA9). Histopathological analysis in patients with a COCH mutation revealed the presence of an acidophylic mucopolysaccharide deposit in the inner ear. An overview of the clinical, pathological and genetic studies on COCH is given, and the possible role of COCH in the pathology of DFNA9 is discussed.