Handbook of Genetic Counseling/AR Sensorineural Hearing Loss (DFNB1/Connexin 26)

AR Sensorineural Hearing Loss (DFNB1/Connexin 26) Introduction Acknowledge prior phone contact What information have you been given already? Have you done any research on your own? What have you found out? What concerns or questions would you like to have answered today? Outline session Complete Medical History Complete Family History and Pedigree Prevalence DFNB1 accounts for 50% of AR sensorineural hearing loss Prevalence is ~14/100,000 1/2000 congenital hearing impairment 70% of these are nonsyndromic 80% of nonsyndromic hearing loss is AR 50% of these are due to GJB2 mutation 1/30 people in general population are carriers Genetics Gene: GJB2 Chromosome location: 13q11-12 Protein: Connexin 26 Gap junction protein Involved in conducing signal to the brain Autosomal recessive inheritance 25% risk of hearing loss for future children 50% risk of being a carrier for the mutation 25% risk of being an unaffected noncarrier Molecular Testing Detects 95% of disease-causing mutations ~66% of mutations - 35delG ~30% of mutations - other GJB2 mutations ~4% mutations - unknown carrier testing is available and can be offered to at-risk family members prenatal testing is available but rarely pursued Clinical Features nonprogressive sensorineural hearing impairment severe to severe-profound hearing loss diagnosed by Auditory Brainstem Response or pure tone audiometry and presence of no related anomalies no other associated health problems no balance problems Management When diagnosis is known or suspected Assessment of auditory acuity by ABR or pure tone audiometry Fitting with hearing aids Early intervention Follow-up care semiannual examination by physician familiar with hereditary hearing impairment repeat pure tone audiometry to confirm stability of loss consideration for cochlear implants Psychosocial Issues Deaf child born to hearing parents How did you feel when you first found out? How have your feelings changed? How have other family members reacted? Have you been in contact with any other families? Have you been in contact with any support groups? Resources American Society for Deaf Children PO Box 3355 Gettysburg, PA 17325 Phone: 717-334-7922 Fax: 717-334-8808 Email: ASDC1@aol.com National Association of the Deaf 814 Thayer Silver Spring, MD 20910 Phone: 301-587-1788 Fax: 305-587-1791 Email: NADinfo@nad.org References Geneclinics: Nonsyndromic Hearing Loss and Deafness, DFNB1 National Information Center on Deafness Clinical Genetics Lecture Notes The information in this outline was last updated in 2002.