As hearing loss increases, speech sounds begin to fall below the detection threshold. Normal conversation is approximately 50 dB, while the loud conversation is closer to 70 dB. Hearing loss of any kind that impairs speech is considered hereditary deafness. Many health care professionals reserve the term "deafness" for people with severe or profound hearing loss. There are several different types of deafness, and these are discussed below.
Jervell and Lange-Nielsen syndrome (JLNS) is a genetic
disorder associated with hereditary deafness and cardiac abnormalities. The
severity of these symptoms varies from person to person, but they are generally
triggered by physical activity, excitement, or fright. A classic symptom of
JLNS is fainting while engaging in physical activity. The syndrome is inherited
as an autosomal recessive trait. Recent product launches and approvals are expected to boost the global hereditary
deafness market growth
Prenatal genetic testing is available to detect
hereditary deafness. DNA is extracted from fetal
cells through amniocentesis at 15 to 18 weeks of gestation or from chorionic
villus samples performed at 10 to 12 weeks. Ultrasound measurements of the
baby's heartbeat, a child's weight, and gestational age are also needed to
correctly determine gestational age. For optimal evaluation, the family of a
deaf person should be identified.
Hereditary deafness is caused by a variety of factors,
and topologists have little to offer in terms of medical and surgical
treatments. A few forms of hereditary deafness may develop later in life. Some
forms are genetically hidden and may manifest at any time in a patient's life.
However, some forms of hereditary deafness are relatively common. These
symptoms should not be ignored, and early genetic testing should be a priority.
In addition to hearing loss, deafness is a common
disability, affecting about 20%–30% of the population. Children affected by deafness
may have other developmental disabilities. In rare cases, genetics may be the
cause of deafness. Autosomal recessive deafness affects boys and girls equally.
People born to deaf parents have a 25% chance of inheriting the deafness gene. However, in May 2021, a research team at Juntendo
University in Japan reported that a stem cell method could be used to treat
common mutation-based hereditary deafness.