Mitochondrial Disorder
What is Mitochondrial
Disease?
Mitochondrial diseases are not one disease, but a group of metabolic
diseases. These diseases result from failures of the mitochondria, specialized
organelles present in almost every cell of the body. Mitochondria are
responsible for providing more than 90% of the energy needed by the body to
sustain life and support growth. Food is converted into ATP (stored energy) by
means of enzymes in the electron transport chain (or respiratory chain) inside
the mitochondria. The process itself is called oxidative phosphorylation.
Defects in either the mitochondrial DNA or the DNA of the nucleus can impair
this process and cause mitochondrial failure.
When mitochondria fail, less and less energy is generated within the
cell. When this happens, cell injury and even cell death follow. If this
process is repeated on a large scale throughout the body, whole systems begin
to fail. The life of the affected person is compromised, changed or even ended.
Hallmark of Mitochondrial
Disease
1. A “common disease” has atypical features that set it
apart from the pack.
2. More than one organ systems are involved.
3. Recurrent setbacks or flare-ups in a chronic disease
occur with infection.
How many individuals are
affected?
Every 15 minutes a child is born who will develop mitochondrial disease
by the age of 10. We now know that this group of diseases is approaching the
frequency of childhood cancers. The exact numbers of children and adults with
mitochondrial disease are hard to determine because of people who suffer from a
mitochondrial disease are misdiagnosed. Some are misdiagnosed with such
conditions as: atypical cerebral palsy, various seizure disorders, other
childhood diseases and diseases of aging, chronic fatigue or fibromyalgia.
What are the causes?
Mitochondrial diseases can be due to inherited mutations or acquired
mutations. There are primary (something inherently wrong with mitochondrial
function) and secondary (the mitochondria are injured as a bystander to another
process) disorders.
Mitochondrial disorders can be inherited in different ways. In fact,
nearly every inheritance “model” known has been demonstrated to occur in
mitochondrial disease. However, most mitochondrial disorders known to date are
inherited in either an autosomal recessive (both parents are unaffected
carriers) or maternal manner.
In many cases, the patient is the only family member affected with a
mitochondrial disease. These cases are called “sporadic” and make answering the
questions regarding inheritance more difficult.
Signs and symptoms
Patients’ symptoms can range from extremely mild to severe, involve one
or more body systems, and can emerge at any age. Most patients’ symptoms
fluctuate over the course of their illness – at some time experience no or few
symptoms while at other times experiencing many and/or severe symptoms.
Symptoms may present unexpectedly at any age, or they may be evident from birth
or infancy. Diseases of the mitochondria appear to cause the most damage to
cells of organs and systems that require a great deal of energy: the brain, the
heart, the skeletal muscles, the GI system, the kidneys, the liver, and the
endocrine and respiratory systems. Many face numerous, severe problems and the
potential for premature death. Mitochondrial diseases are extremely complex;
due to this complexity, the severity of these diseases is unpredictable, and
the range of symptoms is diverse.
Treatment
Even though mitochondrial disorders are long term and currently
incurable, treatments are available. Early treatment of symptoms can reduce
their impact and limit further disability. Avoiding various medications and
stressful situations that worsen symptoms is also helpful. Certain medications
and supplements may improve mitochondrial disease related symptoms – just as
they do for other incurable diseases such as diabetes and emphysema.
Therapeutic interventions, e.g. speech therapy, physical therapy,
occupational therapy, and respiratory therapy, may be necessary for some
mitochondrial disease patients. While they will not change the primary
condition, they may be necessary to preserve and possibly improve current
function, strength and mobility.
Things to Avoid
Physiological “stress”
Stress can cause energy depletion, which may result in temporary, or
sometimes permanent, worsening of the condition. Is it impossible to avoid all
physiologically stressful conditions. However, recognizing what may be
stressful for a patient allows one to adjust the lifestyle.
Cold stress avoidance is extremely important. Thermal regulation
is not always normal in people with mitochondrial diseases and exposure to cold
can result in severe heat loss and trigger an energy crisis. When going out
into the cold, all exposed body parts should be covered, and exposure to extreme
cold should be avoided for anything more than a short period. Over-bundling can
be a problem too.
Heat stress can be a problem in some people. This is especially
true of those with an inability to sweat normally. Heat exhaustion and heat
stroke may occur on hot days. Light clothing is important. Patients should
avoid direct sunlight on hot days and stay indoors if too warm outside. An air
condition environment may be needed.
Lack of sleep may be harmful. Rest is extremely important to
mitochondrial patients.
Illness – especially with fever should be treated as soon
as possible.
Stressors - specific to the individual patient.
Prognosis
It is not possible to chart the future of a person with a mitochondrial
disorder. Those with a higher number of defective mitochondria do worse, on
average, than those with a lesser number, but this is only valid for
populations of patients and cannot be used to predict what will occur in any
one patient.
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