Table IV.

Classification of main genetic hearing loss related syndromes.

GENETIC SYNDROMES
Transmission	Phenotype	Genes involved
Autosomal dominant	WAARDEBURG (2-5% of infant hearing loss) Sensorineural hearing loss, abnormal pigmentation of the skin and hair, dystopia canthorum, heterochromia iridis and pinched nose	Type I, PAX3 Type II, MITF
	BRANCHIO-OTO-RENAL SYNDROME (2% of infant hearing loss) Sensorineural or conductive hearing loss, cup-shaped pinnae, preauricular pits, branchial cleft fistulae and bilateral renal anomalies	-
	STICKLER SYNDROME Progressive sensorineural hearing loss with cleft palate, abnormal development of the epiphysis, vertebral abnormalities and osteoarthritis; myopathy, retinal detachment and vitreoretinal degeneration in Types 1 and 3.	Type I, COL2A1, Type II, COL11A1 Type III, COL11A2
	TREACHER COLLINS Microtia and malformed ears, midface hypoplasia, downslanting palpebral fissures, coloboma of outer 1/3 of lower eyelids, and micrognathia	Treacle
	NEUROFIBROMATOSIS TYPE II Sensorineural hypocusis with cafè-au-lait spots, meningiomas (intracranial and spinal), ependymomas, gliomas, presenile lens opacities, schwannomas (located in the cranial, spinal and peripheral nerves.)	NF2, SCH
Autosomal recessive	USHER SYNDROME (3-5% of infant hearing loss) Several subtypes based on severity of the deafness, vestibular dysfunction and the onset of retinitis pigmentosa (gradual retinal degeneration leading to decreased night vision, loss of peripheral vision, and blindness	Miosina VIIa (for Uscher Ib only)
	PENDRED SYNDROME Sensorineural hearing loss and abnormal iodine metabolism with euthyroid goitre sometimes detected at birth, but often not clinically evident until 8 years of age	SLC26A4 (PDS)
	JERVELL AND LANGE-NIELSEN SYNDROME Severe-profound hearing loss and prolongation of the QT interval	KVLQT1 KCNE1
X-linked	ALPORT SYNDROME Progressive sensorineural hearing loss in addition to renal disorders (glomerulonephritis, haematuria (and renal failure) and ocular abnormalities	COL4A5
Chromosomic condition (trisomia 21)	DOWN'S SYNDROME Every region of the head and neck can be affected. Hearing loss is usually conductive secondary to the chronic middle ear disease or to ossicular chain abnormalities. Other systems affected include cardiovascular, genitourinary, musculoskeletal and ocular
CONGENITAL SYNDROME (Unknown cause)
	GOLDENHAR'S SYNDROME (Oculo-auricolo-vertebral syndrome) Aberrant development of the first and second branchial arches with otologic manifestations include microtia/anotia, and hearing loss (conductive > sensorineural), cardiac abnormalities, ocular abnormalities, hemifacial microsomia and retinal abnormalities