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

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

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

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

transport

USH1C Unknown

CDH23 Intercellular adherence

protein

PCDH15 Cell adhesion molecule

SANS Harmonin associated

protein

USH2A Cell adhesion molecule

VLGR1 G protein–coupled

receptor

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]