Genetic Sensorineural Hearing Loss - 22/08/11
Doi : 10.1016/B978-0-323-05283-2.00148-8
Key Points |
• | It is estimated that at least 50% of congenital hearing impairment has a genetic origin. |
• | A hearing loss can be defined by numerous clinical criteria, including causality, time of onset, age of onset, clinical presentation, anatomic defect, severity, and frequency loss. |
• | The worldwide rate of profound hearing loss is 4 in every 10,000 infants born. |
• | The term homozygosity means that a person carries two identical alleles of a gene; heterozygosity represents the state in which a person carries two different variants of a given gene. |
• | The basic forms of inheritance can be mendelian (single-gene inheritance—autosomal or X-linked), mitochondrial, or complex (chromosomal, new mutations, germline mosaicism, genomic imprinting, polygenic, and multifactorial inheritance). |
• | Nonsyndromic hearing impairment in the absence of other phenotypic manifestations accounts for 70% of hereditary hearing loss. |
• | Mutations in GJB2 have been shown to cause 50% of autosomal recessive nonsyndromic deafness in many world populations. |
• | Syndromic hearing impairment refers to deafness that cosegregates with other features, forming a recognizable constellation of findings known as a syndrome. Sensorineural deafness has been associated with more than 400 syndromes. |
• | The most common syndromic form of hereditary sensorineural hearing loss, Pendred syndrome, is inherited in an autosomal recessive fashion; affected individuals also have goiter. |
• | A well-performed patient history, physical examination, and audiologic evaluation are keys to assessing the cause of hearing loss, and may aid in ascertaining etiology. |
• | Prenatal diagnosis for some forms of hereditary hearing loss is technically possible by analysis of DNA extracted from fetal cells. |
• | Cochlear implantation is becoming an increasingly important option for individuals with severe to profound deafness. |
Plan
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Article précédent
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