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Hearing Loss & Genetics:

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Presentation on theme: "Hearing Loss & Genetics:"— Presentation transcript:

1 Hearing Loss & Genetics:
Understanding the Basics Anna Frangulov, B.S. Research Coordinator Children’s Hospital Boston

2 Why Hearing Loss is So Common?

3 Structure of the Ear

4 Inside the Cochlea “snail”
Sound wave Hair Cells Nerve

5 Structure of the Ear Conductive HL Sensorineural HL

6 What Causes Hearing Loss?
Non-Genetic Infections Drug-Related Traumas/ Exposures Structural Genetic Unknown

7 How Genetic HL occurs?

8 Chromosomes in Nucleus
23 Pairs of Chromosomes MOM DAD

9 One Chromosome Pair Genes “instruction manual”

10 Genes

11 Chromosome Pair Genes Mutation “error”

12 How Is Mutation Inherited?
Dominant ~15% Recessive ~80% X-Linked ~2% Mitochondrial >2%

13 Dominant Inheritance Mutation “error"

14 Carrier Mutation “error"

15 How a Recessive Mutation is Passed?
Carrier –No Hearing Loss Carrier –No Hearing Loss Affected Child— Hearing Loss

16 Recessive Inheritance

17 have normal hearing parents! Recessive Inheritance
90% of all children w/HL have normal hearing parents! Dominant Inheritance Recessive Inheritance Parent w/o HL Parent w/HL Parent w/o HL Child w/HL Child w/ HL If a parent has a dominant mutation, EACH of their children has a 50% chance of having hearing loss If two parents have a recessive mutation, EACH of their children has a 25% chance of having hearing loss


19 HOW Do We Know If HL is Genetic?


21 WHO Should Have a Genetic Test?
Everybody with Sensorineural HL Case A: Syphilis Case B: CMV Case C: Prematurity Case D: High bilirubin level Also 2 Mutations in Cx26!!

22 WHY Should We Have a Genetic Test??
Benefits for Genetic Testing a definite cause family members realize that they are carriers & determine risk factors for future children helps to find appropriate treatment/ management

23 Limitations for Genetic Testing
does not necessarily find the answer severity of HL may not be predicted a person may have mutations, but not have HL

24 Things to Consider Talk to knowledgeable professional
Primary Care/ Pediatrician ENT Audiologist Clinical Geneticist Genetic Counselor Clinical Molecular Geneticist

25 Things to Consider 2. What tests are done? 3. Cost Cx26 Cx30
Mitochondrial Tests Pendred 3. Cost


27 What Does the Result Mean?
Two Mutations are Found No Mutations are Found ~18% ~70% Mutations w/Unknown Significance One Mutation is Found ~10% ~1% ??

28 One Mutation Found Mutation unrelated to deafness
Test did not find 2nd mutation Dominant mutation There may be a mutation in another gene

29 Future in Genetics and HL
More Genetic Tests GeneChip Technology

30 Research Studies Connexin 26 Study- individuals with Cx26 mutations
Genetic Testing and Counseling Study - If you or your child has had genetic testing for hearing loss and you are willing to fill out a questionnaire GeneChip Study - individuals with hearing loss who and parents with normal hearing Novel Gene Discovery Study - five or more family members with hearing loss

31 Educational Material Now also in Spanish!

32 Helpful Information Genetic Counselor - Rebecca Madore call to set an appointment or Department of Clinical Genetics – To make appointment with Clinical Geneticist call National Society of Genetic Counselors (NSGC) Research Study Participation & Booklets Orders: Anna Frangulov or

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