Handbook of Genetic Counseling/AR Sensorineural Hearing Loss (DFNB1/Connexin 26)
AR Sensorineural Hearing Loss (DFNB1/Connexin 26)
- 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
- 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
- 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
- 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
- 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
- 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
- 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?
- 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
- Geneclinics: Nonsyndromic Hearing Loss and Deafness, DFNB1
- National Information Center on Deafness
- Clinical Genetics Lecture
The information in this outline was last updated in 2002.