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GENETICS AND HEARING LOSS Submitted by Kathleen Corbin, M.A., CCC-A, Audiologist for the ISHA Fall Conference, September 21, 2013 Over one in every 500 infants has or will develop a hearing loss in early childhood GENETIC HEARING LOSS – approx. 50% to 60% of all with hearing loss MODE OF TRANSMISSION 80% Recessive 15% Dominant 2% x-linked 2% Mitochondrial CATEGORIES OF GENETIC HEARING LOSS Non-Syndromic (70%) Syndromic (30%) NON-SYNDROMIC Common mutation sites GJB2 (Gap Junction Protein, Beta 2) gene (Causal factor of 40% of non-syndromic hearing loss) – Myosin VI TECTA GENETICS and HEARING LOSS K. Corbin, p. 2 SYNDROMIC DEAFNESS More than 600 different syndromes identified Auditory Profile Conductive, sensor neural or mixed Unilateral or bilateral Symmetrical or asymmetrical Progressive or stable COEXISTENT DEFICITS Cardiovascular Renal Neurologic Pulmonary Ophthalmic Orthopedic Endocrine Immunologic SYNDROMIC HEARING LOSS INHERITED VIA RECESSIVE TRANSMISSION USHER SYNDROME Most common eye/ear disorder Estimated 10% of all children with SNHL Hearing loss Type I: Absent vestibular function Severe to Profound SNHL Type II: Moderate to Severe SNHL Type III: Progressive SNHL Retinitis Pigmentosa PENDRED SYNDROME Estimated at 5% of all children with hearing loss Profound sensor neural hearing loss (cochlear) Vestibular Dysfunction Thyroid defect, goiter GENETICS and HEARING LOSS K. Corbin, p.3 JERVELL and LANGE-NIELSON SYNDROME Profound SNHL Cardiac abnormality Recurrent drop attacks Sudden death INHERITED VIA DOMINENT TRANSMISSION WAARDENBURG SYNDROME Estimates of 2.3% of all children with hearing loss Type I appearance of widened nasal bridge -20% with SNHL; Type II no appearance of widened nasal bridge - 50% with hearing loss Pigmentary abnormalities White forelock Partial albinism Early graying TREACHER COLLINS Conductive hearing loss Craniofacial anomalies Eyelid colobomas STICKLER SYNDROME More prevalent in the Midwest region of the United States Hearing loss due to Eustachian tube dysfunction secondary to palatal anomalies; SNHL which may be progressive or conductive anomalies have been noted Flattening of the facial profile Cleft palate Myopia/retinal detachment/cataracts Neuropathy BRANCHIO-OTO-RENAL SYNDROME (BOR) Estimated in 2% of all children with profound SNHL Hearing loss is present in 75% of patient with BOR CHL (30%) SNHL (20%) Mixed (50%) Malformation of the pinnate and preauricular pits Renal anomalies are markedly varied and may be asymptom GENETICS and HEARING LOSS K. Corbin, p.4 NEUROFIBROMATOSIS II Vestibular schwannomas with secondary hearing loss and other intracranial tumors 45% - 50% have accompanying hearing loss 75% have unilateral hearing loss Hearing loss is neural or central INHERITED VIA X-LINKED TRANSMISSION Alport Syndrome Incidence estimated at 1% of all children with hearing loss Progressive SNHL (High-frequency; Cochlear) Progressive Nephritis Lens Abnormalities Renal and Hearing impairment usually manifest in adolescence or early adult years INHERITED VIA MITOCHONDRIAL DISORDERS Kearns-Sayre syndrome Incidence unknown Neuromuscular disease SNHL NON-GENETIC HEARING LOSS (30%) Maternal Influences Infection – viral or bacterial Substance abuse Environmental exposure Birth Complication Respiratory distress/perinatal asphyxia Hyperbilirubinemia Hemorrhage perinatal or intraventricular COMBINATION OF GENES AND ENVIRONMENT (10%) Ototoxicity-Induced SNHL from Aminoglycoside Exposure Noise-Induced SNHL from Excessive Noise Exposure