Ataxia (Ataxia-telangiectasia)
Also called: Louis-Bar
Syndrome
What is it?
Ataxia refers to a group of
nervous system disorders marked by loss of muscle
control. Ataxia-telangiectasia
is a rare genetic disease that affects multiple
systems and causes loss of balance and
coordination.
The word “ataxia” means lack of muscle
control and “telangiectasia” means tiny, red
spots, both of which characterize this disease. A
child who has inherited A-T will display nervous
system abnormalities by age 2, and will then
progressively lose muscle control. Friedreich's
Ataxia (FA) is the most common inherited ataxia,
with symptoms generally appearing between the ages
of 8 and 15.
Who gets it?
A-T is very rare.
It affects only about 500 people in the
United States.
Friedreich's ataxia affects 3,000 to 5,000 people in the
United States. If you have one child with FA, you
will have a 25% chance of conceiving another
affected child.
What causes it?
Ataxia can be caused by birth
trauma, a congenital disorder, infection, a
degenerative disorder, tumor, exposure to a toxic
substance, or head injury.
Congenital ataxia is an autosomal recessive
disease, which means that both parents must carry
the defective gene and a child must inherit one
defective gene copy from each parent to develop
symptoms. An
estimated 0.5 - 1.4% of the population
(approximately 2.5 million people) carry one copy
of the mutated gene. While carriers will not show
symptoms of ataxia, they may experience increased
radiation sensitivity and higher cancer rates. A
person with only one defective gene copy may pass
the gene along to offspring. Scientists have
identified the gene that causes A-T and have named
it the “ATM” gene, Ataxia-Telangiectasia
Mutated. Those
with FA have defects in the frataxin gene.
Extra DNA, called a “triple repeat,”
interferes with normal production of frataxin,
which is involved in regulating the transport of
iron. Researchers
believe symptoms are caused when the defects in
iron transport interfere with the efficient use of
cellular energy supplies.
What are the symptoms?
At first, infants with A-T
appear healthy. By
age 2, however, parents notice increased
clumsiness and balance problems. As
symptoms become progressively worse, speech
becomes slurred and difficult. Between
ages 2 to 8, the telangiectases - tiny, red
“spider” veins - appear on the cheeks, ears,
and in the eyes.
By age 10 to 12, children with A-T lose
muscle control. Other
symptoms can vary, but include immune system
deficiencies, missing or abnormally developed
thymus gland, retarded growth, diabetes,
prematurely graying hair, and difficulty
swallowing. Those
with A-T are of normal intelligence. As
the children grow older, the immune system becomes
weaker and is less capable of fighting infection. In
the later stages of the disease, patients often
suffer from recurring respiratory infections and
blood cancers, such as leukemia or lymphoma.
A-T is fatal. Children with A-T are
physically disabled by their early teens and
typically die by their early twenties.
In very rare cases, individuals may survive into their
thirties.
Symptoms of FA usually first
appear between the ages of 8 and 15.
However, symptoms have been observed as
early as 18 months or as late as age 25.
The nerve cells in the spinal cord that relay information
between the muscles and the brain are most
affected by FA. This causes movements to become
uncoordinated and jerky.
The first symptom is usually a lack of
coordination when walking, such as bumping into
doorways or tripping over low obstacles. Children
are often unsteady when standing still and have a
poor sense of position. Because
the muscles in the legs are weak in some areas and
stronger in others, children often develop foot
deformities and walk on their toes. Within several
years, the child will experience ataxia in the
arms, causing decreased hand-eye coordination. Other
common symptoms include muscle spasms and cramps,
speech and swallowing difficulties, diabetes
mellitus, nystagmus (eye tremor), vision loss,
hearing loss, and curvature of the spine
(scoliosis).
About two thirds of patients suffer from
heartbeat arrhythmias, causing shortness of breath
after exertion, swelling in the lower limbs, and
feelings of cold feet. As
with A-T, immune system deficiencies and blood
cancers are common. Those with FA are also
extremely sensitive to radiation.
FA progresses at a variable rate. Most
patients lose the ability to walk within 15 years
after symptoms begin. Ninety-five percent need a
wheelchair by age 45. The
average age of death is in the mid-thirties, but
may be as late as the mid-sixties.
How is it diagnosed?
Diagnosis of A-T is based
upon the observation of progressive ataxia and
telangiectasia. 70%
of individuals with A-T also have a high incidence
of respiratory infection. Because
scientists have identified the ATM gene, screening
and, eventually treatment, may be possible in the
future.
To diagnosis FA, your
physician will take a thorough medical history and
perform a neurological exam.
Lab tests can include electromyography, an electrical test of
muscle, and a nerve conduction velocity test.
Because heart arrhythmia is a symptom of FA, an
electrocardiogram may also be performed.
Direct DNA testing for FA is available, so
FA is easier to distinguish than other types of
ataxia. Your
physician can even use the same test to check for
the presence of the genetic defect in siblings who
are unaffected.
What is the treatment?
There is currently no cure
for A-T or FA.
While there is no treatment that will slow
its progress, various forms of physical, speech,
and occupational therapy can help patients adapt
to the symptoms.
With A-T, injections of gamma globulin, extracts of
human blood that contain antibodies, may
strengthen the weakened immune system. Your
physician may also prescribe high doses of
vitamins. For
patients with FA, the drug amantadine may offer
limited improvement in muscle control, but is not
recommended in patients with any cardiac
abnormalities. For some patients, arm weights can
help control the most spastic arm movements.
Other symptoms, such as heart arrhythmias
and diabetes, are treated with appropriate drugs.
Self-care tips
There is no way to prevent
development of T-A or FA in a person carrying two
defective gene copies.
However, because the genes that cause the
diseases have been identified, researchers are
investigating methods for screening individuals
who may be carriers of the defective gene. Prenatal
testing for A-T is possible but is not done
routinely because commercial screening tests have
not been developed.
This information has been designed as a comprehensive and quick reference
guide written by our health care reviewers. The health information written
by our authors is intended to be a supplement to the care provided by your
physician. It is not intended nor implied to be a substitute for
professional medical advice.
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