Chapter 030. Disorders of Smell, Taste, and Hearing (Part 8)

The contribution of genetics to presbycusis (see below) is also becoming better understood. In addition to GJB2, several other nonsyndromic genes are associated with hearing loss that progresses with age. Sensitivity to aminoglycoside ototoxicity can be maternally transmitted through a mitochondrial mutation. Susceptibility to noise-induced hearing loss may also be genetically determined.There are 400 syndromic forms of hearing loss.
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Chapter 030. Disorders of Smell, Taste, and Hearing (Part 8) Chapter 030. Disorders of Smell, Taste, and Hearing (Part 8) The contribution of genetics to presbycusis (see below) is also becomingbetter understood. In addition to GJB2, several other nonsyndromic genes areassociated with hearing loss that progresses with age. Sensitivity toaminoglycoside ototoxicity can be maternally transmitted through a mitochondrialmutation. Susceptibility to noise-induced hearing loss may also be geneticallydetermined. There are >400 syndromic forms of hearing loss. These include Ushersyndrome (retinitis pigmentosa and hearing loss), Waardenburg syndrome(pigmentary abnormality and hearing loss), Pendred syndrome (thyroidorganification defect and hearing loss), Alport syndrome (renal disease andhearing loss), Jervell and Lange-Nielsen syndrome (prolonged QT interval andhearing loss), neurofibromatosis type 2 (bilateral acoustic schwannoma), andmitochondrial disorders [mitochondrial encephalopathy, lactic acidosis, andstroke-like episodes (MELAS); myoclonic epilepsy and ragged red fibers(MERRF); progressive external ophthalmoplegia (PEO)] (Table 30-4). Table 30-4 Syndromic Hereditary Hearing Impairment Genes Syndrome Gene Function Alport syndrome COL4A3- Cytoskeletal protein 5 BOR syndrome EYA1 Developmental gene SIX1 Developmental gene Jervell and Lange- KVLQT1 Delayed rectifier K+Nielsen syndrome channel KCNE1 Delayed rectifier K+ channelNorrie disease Norrin Cell-cell interactionsPendred syndrome SLC26A4 Chloride/iodide transporterTreacher Collins TCOF1 Nucleolar-cytoplasmic transportUsher syndrome MYO7A Cytoskeletal protein USH1C Unknown CDH23 Intercellular adherence protein PCDH15 Cell adhesion molecule SANS Harmonin associated protein USH2A Cell adhesion molecule VLGR1 G protein–coupled receptor USH3 UnknownWS type I, III PAX3 Transcription factorWS type II MITF Transcription factor SLUG Transcription factorWS type IV EDNRB Endothelin-B receptor EDN3 Endothelin-B receptor ligand SOX10 Transcription factor Note: BOR, branchio-oto-renal syndrome; WS, Waardenburgsyndrome.[newpage]