Учебники / Genetics and Auditory Disorders Keats 2002

may overlook them. Had the diagnosis of Waardenburg syndrome type II been missed, one might have assumed the chance for S.K. to have deaf children was greater or less than the actual chance of 25%. This case also addresses the notion of the family, and not the individual, as the patient. A diagnosis of a genetic condition in an individual may have profound health or reproductive implications for other family members.

6.3 Case 3

T.R. (a 23-month-old Hispanic female) and her brother J.R. (a 4-month-old Hispanic male) were referred for a genetic work-up by their audiologist because of recent identification of sensorineural hearing loss.

6.3.1 Medical History

T.R. and J.R.’s prenatal, birth, and medical histories are unremarkable. T.R.’s mother reported that T.R. has had an ophthalmological examination and CT scan of the temporal bones since the hearing loss was diagnosed. Both were reported to be within normal limits.

6.3.2 Audiologic Findings

Because of concerns about speech development, T.R. had an ABR at age 18 months, which indicated a sloping, moderate to severe sensorineural hearing loss bilaterally. Follow-up sound field testing is consistent with the ABR results. Pure-tone averages are 60 on the right and 55 on the left. J.R. had an ABR at age 2 months because of his sister’s hearing loss. A bilateral, moderately severe sensorineural hearing loss is suspected. Both children are being fitted for hearing aids.

6.3.3 Family History

As shown in Figure 9.3, all other family members, including the parents and a half-brother, are hearing. The family history is unremarkable.

6.3.4 Physical Examination

T.R.’s physical examination revealed slight micrognathia, but was otherwise unremarkable. J.R.’s physical examination was within normal limits with no evidence of a genetic syndrome.

6.3.5 Clinical Diagnosis and Recommendations

A diagnosis of autosomal-recessive, nonsyndromic, sensorineural hearing loss was made. Records from T.R.’s examinations following the diagnosis of hearing loss were requested to confirm that they were within normal limits.

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FIGURE 9.3. Family history of T.R. and J.R. who were diagnosed with autosomalrecessive, nonsyndromic hearing loss.

6.3.6 Genetic Counseling Issues

Genetic counseling in this situation would include a discussion of autoso- mal-recessive inheritance. Any future children T.R. and J.R.’s parents may have would have a 25% chance of having a hearing loss. The chance for T.R. and J.R. to have children with hearing loss depends on how frequent the gene causing their hearing loss is in the population, whether they marry a person with a hearing loss, and the cause of their mates’ hearing loss, if any. Both T.R. and J.R. would be encouraged to seek genetic counseling again at the time they are considering marriage or children.

Issues regarding how the parents feel about their child’s hearing loss would be explored. Feelings of guilt or blame (“It’s my fault my children are deaf”) may be present. Referral to a support group or counseling may be beneficial. The parents may also have many questions about educational and language choices for their children, and appropriate referrals would be made.

This family would be referred to a genetics center performing molecular genetic studies of nonsyndromic deafness. Families agree to participate in research for different reasons. Although this family may receive no apparent immediate benefit from participation in research, it may be of benefit to family members in years to come. Identification of the gene for hearing loss present in the family may assist the parents with dealing with their feelings about passing deafness on to their children. It may also allow

genetic counselors to provide information about possible progression of the hearing loss, which may be important in making educational and language choices. Identification of a gene for nonsyndromic deafness in these children would also alleviate any concerns the parents may have about the possibility of future medical complications associated with syndromic forms of deafness and eliminate costly testing done to diagnose these complications.

6.3.7 Overview of Case 3

This case demonstrates the issues facing hearing parents with deaf children, which differ from those facing deaf adults. These parents may be grieving the loss of their “perfect” child. They may also feel unequipped to care for a deaf child and overwhelmed by the number and importance of decisions they must make. Deaf adults have often been deaf their entire lives and never experienced a loss and therefore likely do not require emotional support.

This case also demonstrates that hearing couples with young deaf children may seek molecular genetic testing for reasons different from an adult deaf couple (such as the couple in Case 1). In addition to identifying a specific form of hearing loss and allowing for more accurate genetic counseling, genetic testing may eliminate the need for some costly, time-consuming medical evaluations, and provide information about possible progression of the hearing loss.

7. Summary

Genetic counseling is the process of providing information to families about a genetic condition such as deafness in an atmosphere that is non-directive, supportive, and sensitive to the special needs of individuals. Professionals who provide health care and services to deaf and hard of hearing children and adults are essential to the referral process. Genetic counseling includes the collection of medical and family history information, a physical examination by a certified clinical geneticist, referral for genetic diagnostic tests offered on a research or clinical basis, and referral and follow-up for any medical conditions that are found to be associated with the deafness. Families are also provided with detailed information regarding the cause of the deafness, treatment options and reproductive implications, and are given support and guidance in making decisions about these options. The availability of genetic testing for many hereditary forms of deafness has improved the ability of genetic counselors and clinical geneticists to provide accurate information to families. However, there are many ethical implications of this type of testing yet to be explored. These considerations are particularly important given that some deaf people identify themselves as being part of a separate cultural group based on their deafness.

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References

Ad Hoc Committee on Genetic Counseling (1975) Genetic Counseling. Am J Hum Genet 27:240–242.

Arnos KS, Cunningham M, Israel J, Marazita M (1992) Innovative approach to genetic counseling services for the deaf population. Am J Med Genet 44:345–351.

Arnos KS, Israel J, Cunningham M (1991) Genetic counseling for the deaf: Medical and cultural considerations. Ann New York Aca Sci 630:212–222.

Bieber FR, Nance WE (1979) Hereditary hearing loss. In: Jackson LG, Schimke RN (eds) Clinical Genetics. New York: John Wiley & Sons, p. 456.

Jordan IK (1991) Ethical issues in the genetic study of deafness. Ann New York Aca Sci 630:236–239.

Middleton A, Hewison J, Mueller RF (1998) Attitudes of deaf adults toward genetic testing for hereditary deafness. Am J Hum Genet 63:1175–1180.

Nance WE (1993) Parables. In: Bartels DM, LeRoy BS, Caplan AL (eds) Prescribing Our Future. Ethical Challenges in Genetic Counseling. New York: Aldine De Gruyter, pp. 89–94.

Padden C, Humphries T (1988) Deaf in America: Voices from a Culture. Cambridge, MA: Harvard University Press, pp. 1–134.

Schein JD (1989) At Home Among Strangers. Washington, DC: Gallaudet University Press, pp. 106–134.

Sill AM, Stick MJ, Prenger VL, Phillips SL, Boughman JA, Arnos KS (1994) A genetic epidemiologic study of hearing loss in an adult population. Am J Med Genet 54:149–153.