Deafness

Abstract

Recent statistical data indicate that in western countries, at least 1:1000 suffer from congenital hearing impairment. Genetic factors are responsible for more than 60% of the congenital cases. However, hearing loss is a multifactorial disorder caused by both genetic and environmental factors. Molecular genetics of deafness has experienced remarkable progress in the last decade. Genes responsible for hereditary hearing impairment are being identified progressively. This article, reporting some syndromic conditions related to deafness, focuses on nonsyndromic hearing loss. Genes involved in this type of pathologic conditions have only recently begun to be identified. Owing to genetic heterogeneity, private nature of most mutations and large size of most deafness genes, the molecular diagnostic possibilities in recessive deafness are today available for a number of genes. Facility and benefits of genetic tracking should be an important public health issue, so that determinations of early diagnosis of hearing loss can be established. Key Concepts Deafness is the most common sensory deficit in humans, affecting 1 in 1000 newborn, and to date more than 23 different DFNB proteins have been discovered. DFNB proteins can be classified into two classes: (1) genes regulating potassium homeostasis and (2) genes producing proteins that are important in the formation of stereocilia. Mutation in the same gene can give rise to different phenotypes: we can have either deafness associated with a dermatologic disease or only deafness. The same gene mutation can lead to different clinical presentations, indicating that the knowledge of molecular genetics has not reached the details of auditory neurological‐related physiology. Owing to genetic heterogeneity, the molecular diagnostic possibilities in recessive deafness are still limited. However, facility and benefits of genetic tracking should make them an important public health issue.