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. These include Usher syndrome (retinitis pigmentosa and hearing loss), Waardenburg syndrome (pigmentary abnormality and hearing loss), Pendred syndrome (thyroid organification defect and hearing loss), Alport syndrome (renal disease and hearing loss), Jervell and Lange-Nielsen syndrome (prolonged QT interval and hearing loss), neurofibromatosis type 2 (bilateral acoustic schwannoma), and mitochondrial disorders [mitochondrial encephalopathy, lactic acidosis, and stroke-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- 5 Cytoskeletal protein BOR syndrome EYA1 Developmental gene SIX1 Developmental gene Jervell and Lange- Nielsen syndrome KVLQT1 KCNE1 Delayed rectifier K + channel Delayed rectifier K + channel Norrie disease Norrin Cell-cell interactions Pendred syndrome SLC26A4 Chloride/iodide transporter Treacher Collins TCOF1 Nucleolar-cytoplasmic transport Usher 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 Unknown WS type I, III PAX3 Transcription factor WS type II MITF Transcription factor SLUG Transcription factor WS type IV EDNRB Endothelin-B receptor EDN3 Endothelin-B receptor ligand SOX10 Transcription factor Note: BOR, branchio-oto-renal syndrome; WS, Waardenburg syndrome.[newpage] . Chapter 030. Disorders of Smell, Taste, and Hearing (Part 8) The contribution of genetics to presbycusis (see below) is also becoming. organification defect and hearing loss), Alport syndrome (renal disease and hearing loss), Jervell and Lange-Nielsen syndrome (prolonged QT interval and hearing loss), neurofibromatosis type 2. are >400 syndromic forms of hearing loss. These include Usher syndrome (retinitis pigmentosa and hearing loss), Waardenburg syndrome (pigmentary abnormality and hearing loss), Pendred syndrome