Biology Reference
In-Depth Information
a daughter with a high-frequency hearing loss. M.S.'s other nieces and
nephews are hearing. M.S.'s mother is hearing, and her father has a high-
frequency hearing loss. His paternal grandfather was said to be “very hard
of hearing.” No audiometric information to document degree or progres-
sion of the hearing loss is available for these relatives.
D.S. is one of four deaf siblings and is the product of deaf parents (Fig.
9.1). One of his sisters married a deaf man from a deaf family and has two
deaf sons. Another sister married a deaf man with a family history of deaf-
ness and has one deaf and one hearing child. The third sister married a
hearing man of deaf parents and has one hearing son. D.S.'s parents each
have a deaf brother and other hearing siblings. They were both born to
hearing parents.
6.1.4 Physical Examination
M.S. is a petite woman who is said to be smaller than her siblings. Fundus-
copic examination revealed mottled coloration of her retinas. There was
no audible heart murmur. The rest of the examination was within normal
limits. D.S.'s physical examination was within normal limits with no evi-
dence of a genetic syndrome.
6.1.5 Clinical Diagnosis and Recommendations
M.S. was diagnosed as having congenital rubella syndrome (Table 9.2). D.S.
was diagnosed as having nonsyndromic, autosomal recessive, sensorineural
hearing loss. It is also likely that an autosomal-dominant form of nonsyn-
dromic sensorineural hearing loss is present in M.S.'s family.
6.1.6 Genetic Counseling Issues
Genetic counseling in this situation would include a discussion of congen-
ital rubella syndrome (CRS) and why this is the likely cause of M.S.'s deaf-
ness. There is a 50% chance that M.S. has also inherited the gene for
autosomal-dominant high-frequency hearing loss from her father, but that
it is masked by the CRS. If she has inherited the gene, there is a 50/50 chance
with each pregnancy that she will pass on that gene to her child.
TABLE 9.2. Congenital rubella syndrome
Fetal exposure to a maternal rubella infection may cause changes in several organ systems,
most commonly the ear, heart, and eyes. Infants may have a sensorineural deafness. They
may have a congenital heart defect, usually patent ductus arteriosus, pulmonary stenosis,
ventricular septal defect, or atrial septal defect. Common eye findings in congenital rubella
syndrome (CRS) are cataracts and congenital glaucoma. Other features associated with
CRS include small stature, jaundice, enlarged liver and spleen, small head, learning
disabilities or mental retardation, anemia, low platelet count, changes in the hardening of
the long bones, and a rash.
