Biology Reference
In-Depth Information
3.4 Physical Examination
A clinical geneticist certified by the American College of Medical Genet-
ics is qualified to perform a physical examination as part of the genetics
evaluation. The clinical geneticist is trained to recognize specific traits, fea-
tures, and aspects of the family history that may lead to a specific diagno-
sis of the cause of hearing loss. This person assimilates information from
the family history, medical history, and results of the physical examination
in making a diagnosis. A genetic examination may contain aspects that are
similar to other physical examinations, such as listening to the heart and
looking in the ears; but a genetic evaluation also includes more observa-
tions (of eye color, ear shape, etc.) and measurements (of the head cir-
cumference, eyes, etc.). Since many deaf individuals who are referred for
genetic evaluation have syndromic forms of hearing loss, the clinical geneti-
cist will pay special attention to the presence of any physical features such
as goiter; pigmentary abnormalities of the eye, hair, or skin; severe myopia;
fainting spells or heart disease; abnormalities of the external ears, face, or
skeletal structures; or evidence of kidney disease or eye disease.
3.5 Additional Medical Studies or Referral to Specialists
The clinical geneticist may recommend evaluations by other specialists or
additional laboratory tests based on the findings. For example, a person with
hearing loss who is found to have ear pits or tags will be referred for a renal
ultrasound when a diagnosis of branchio-oto-renal syndrome is considered.
A deaf child who is found to have difficulty with night blindness or who has
pigmentary retinopathy will be referred to an ophthalmologist. In fact, a
formal ophthalmologic evaluation is recommended even in children who
appear to have isolated sensorineural hearing loss because of the educa-
tional significance of the progressive loss of vision associated with Usher
syndrome. Children who have a history of syncopal episodes would be
referred to a cardiologist to rule out prolonged QT, associated with Jervell
and Lange-Nielsen syndrome. An adult with a progressive hearing loss
and cataracts may be referred for a urinalysis to check for hematuria when
Alport syndrome is suspected. A chromosome study may be recommended
for a deaf child who has multiple malformations involving other organ
systems. There are many other tests or referrals that may be indicated based
on the findings of the clinical geneticist.
3.6 Screening for Genes for Deafness/Referral to
Research Protocols
Knowledge of the molecular genetics of hearing loss is growing rapidly. The
chromosomal locations of dozens of genes causing both syndromic and non-
