Ambassador of Horsham Pennsylvania
Mitochondrial Disease And Deafness
Genetic factors are thought to cause
more than 50% of all incidents of congenital hearing loss in
children. (Canalis and Lambert, 2000) Hearing loss that is
congenital have three causes; autosomal dominant, autosomal
recessive and X-linked hearing. Today I will be focusing on an
autosomal dominant/autosomal recessive cause; Mitochondrial Disease.
Mitochondria produce the energy our bodies need to
sustain life. When these compartments fail they cause injury or
complete failure of the organ affected. Mitochondria are very
complex organelles located in virtually all cells of the body.
Neither the mitochondria nor the cell can exist without the other.
Interestingly, mitochondria have a separate set of genes that are
not part of the cell's genes. Changes in the mitochondrial genes can
also result in syndromes involving hearing loss. Hearing Loss and
Deafness are symptoms of Mitochondrial Disease.
Sensorineural hearing loss is the most common type of
permanent hearing loss and the main cause of hearing impairments of
those with mitochondrial diseases. Sensorineural hearing loss can be
mild, moderate, or severe, including total deafness and is almost
always permanent. Abnormalities in the hair cells in the cochlea are
the main cause of Sensorineural Hear Loss Some patients may also
have abnormalities in the central auditory system of the brain
There are many defects of the Mitochondria that will
cause hearing impairment. One of these is known as MERRF or
myoclonic epilepsy and Ragged-Red Fiber Disease. MERRF is a
progressive multi-system syndrome usually beginning in childhood,
but onset may occur in adulthood. The rate of progression varies
widely (UMDF, 2012)
Another common cause is KSS or Kearns-Sayre
Syndrome. KSS is a slowly progressive multi-system mitochondrial
disease. The main symptoms include paralysis of the eye muscle,
cardiac blocks, ataxia and deafness. KSS is a very rare disorder.
One online eMedicine article found only 226 cases worldwide in the
literature by 1992 Kearns-Sayre Syndrome by Ewa Posner,MD)
Defects in the Mitochondrial Complexes are one also
another cause of deafness. This is the case in mainly Complex I and
Complex III disorders. These disorders are mainly autosomal
recessive. Hearing loss is also accompanied by weakness, short
stature, ataxia and dementia.
When it comes to Deaf culture, we realize there is a
dividing barrier between those who are deaf and hearing. That would
be communication. Many patients affected by deafness due to
mitochondrial disease never get the chance to take a part in Deaf
Culture. Lack of muscle strength and developmental delays make it
hard for most to learn sign language or other means of
communication. Deafness due to mitochondrial disease happens most
often at birth. The child never has the opportunity to learn so they
basically have very little ability to communicate.
Mitochondrial Disease is something that is very close to
home for me because I myself suffer from it. I may not have hearing
loss but could be affected by it sometime in the future. There
really isn't enough research to tell me how things will pan out. I
do not have one of the disorders listed above but that does not
lessen my chance of losing my hearing. I chose to learn about the
Deaf Culture not only because I have a huge interest in it, but it
also may be my future.
My Baby's Hearing.Boy
Town National Research Hospital. 20 May 2012
Hearing Loss." Medscape. Meyers,Arlene 12 April 2012 http://emedicine.medscape.com/article/856116-overview
American Academy of Otolarynogoly-Head and Neck
Surgery. 13 October 2011
"Hearing Loss in Mitochondrial Disorders."
Georgetown University Medical Center. 2005
Causes Of Hearing Loss in Children.American
Speech Language Association. 1997-2012
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