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QUESTIONS AND ANSWERS
What is Myotonic Muscular Dystrophy?
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Weakness
and wasting of voluntary muscles in the face, neck, and
lower arms and legs are common in myotonic muscular dystrophy.
Muscles between the ribs and those of the diaphragm, which
moves up and down to allow inhalation and exhalation of
air, can also be weakened. |
Myotonic muscular dystrophy (MMD) is a form of
muscular dystrophy that affects muscles and many other organs
in the body. Unlike some forms of muscular dystrophy, MMD often
doesn’t become a problem until adulthood and usually allows
people to walk and be pretty independent throughout their lives.
The infant form of MMD is more severe. Unfortunately,
it can occur in babies born to parents who have the adult form,
even if they have very mild cases.
The word myotonic is the adjective for
the word myotonia, an inability to relax muscles at will.
In MMD, the myotonia is usually mild. In fact, many people attribute
it to “stiffness” or think they have arthritis. If
anything is noticeable, it’s usually difficulty with one’s
grip, for example when using a tool or writing instrument.
Myotonia isn’t a feature of any other form
of muscular dystrophy (although it occurs in other kinds of muscle
diseases, where it can be severe). When a person suspected of
having muscular dystrophy has myotonia, the diagnosis is likely
to be MMD.
The term muscular dystrophy means slowly
progressive muscle degeneration, with increasing weakness and
wasting (loss of bulk) of muscles. The weakness and wasting of
muscles generally present much more of a problem to people with
MMD than does the myotonia. However, they usually aren’t
as severe as in some other types of muscular dystrophy.
MMD symptoms sometimes begin at birth. Infants
with this disorder, congenital MMD, have severe muscle
weakness, including weakening of muscles that control breathing
and swallowing. These problems can be life-threatening and need
intensive care. Myotonia isn’t part of the picture in infants
with MMD.
MMD symptoms can also begin in children past infancy
but not yet adolescents, although this is unusual. Generally,
the earlier MMD begins, the more severe the disease is.
Myotonic muscular dystrophy is often known simply
as myotonic dystrophy and is occasionally called Steinert’s
disease, after a doctor who originally described the disorder
in 1909. It’s also called dystrophia myotonica,
a Latin name, and therefore often abbreviated "DM."
MMD varies greatly in severity, even within the
same family. Not everyone has all the symptoms and not everyone
has them to the same degree.
There is, however, a distinct difference between
the type that affects newborn infants — congenital MMD —
and the type that begins in adolescence or adulthood — adult-onset
MMD.
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What Causes Myotonic Muscular Dystrophy?
Myotonic muscular dystrophy is caused when a portion
of either of two genes is larger than it should be. See "Does
It Run in the Family?" to find out what scientists understand
about how these genetic flaws cause MMD.
The chromosome 19 form of the disease,
now called type 1 MMD (MMD1), is the most common, and
most of this booklet describes that form.
Type 2 MMD (MMD2), arising from an abnormality
on chromosome 3, is less common, generally less severe,
but not as well understood as the chromosome 19 form. Most of
the information in this booklet is derived from studies of people
with type 1 MMD.
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What Happens in Adult-Onset MMD?
It’s reassuring to know that when MMD begins
in the teen years or during adulthood, it’s often only a
moderately disabling condition with very slow progression. As
one doctor put it, "Some people with MMD go through much
of their lives without troubling or being troubled by the medical
profession."
There can be troubling symptoms, however, for
many people. Although many different parts of the body can be
affected by MMD, most people with the disease have only some of
the following symptoms. Most of the problems can be lessened with
medical treatment.
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Limb Muscles
Weakness of the voluntary muscles, such
as those that control the arm and legs, is usually the most
noticeable symptom for people with adult-onset MMD.
The distal muscles — those
farthest from the center of the body — are usually
the first, and sometimes the only, limb muscles affected.
The forearms, hands, lower legs and feet are the parts of
the body that have these distal muscles. Over time, these
muscles get smaller, so the lower legs and arms may appear
thinner than the upper legs and arms.
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| A wrist support can hold the hand
in a good position for using a keyboard, writing or
drawing. |
People with MMD often notice that their
grip is weak and that they have trouble using their wrist
or hand muscles. At the same time, the muscles that pick
up the foot when walking weaken, so the foot flops down,
leading to tripping and falling. This is called foot
drop.
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| An ankle-foot orthosis (AFO) can
keep the foot from flopping down and causing falls. |
Some people can compensate for weak foot
muscles by picking up the foot from the knee and walking
with a “marching” step. Eventually, though,
many people with MMD find that a cane or walker is helpful
to compensate for foot and leg weakness.
A lower leg brace, called an ankle-foot
orthosis or AFO, may be needed. A few people
with MMD use a wheelchair or a power scooter for convenience
when covering long distances.
Various devices that hold the hand in a
good position for using a keyboard or writing or drawing
can help compensate for weak wrist and hand muscles. |
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Head, Neck and Face Muscles
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| A long, thin face with hollow temples,
drooping eyelids and, in men, balding in the front, is typical
in myotonic dystrophy |
The muscles of the neck, jaw and parts of the
head and face may weaken, especially in MMD1. Weakness and loss
of bulk in these muscles leads to a characteristic appearance
doctors and experienced family members recognize as MMD. In men,
early balding in the front part of the scalp is very common, adding
to the distinct appearance of MMD.
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| Special glasses with "crutches"
to hold skin away from the eyes can help when muscles in this
area are weak. |
Eyelids may droop (called ptosis, but
the “p” is silent), the temples appear hollow, and
the face looks long and thin.
Severe ptosis can be troubling. It may be hard
to hold the eyes open for reading, watching television or driving.
Special glasses with “eyelid crutches” can hold the
eyes open. You can’t buy these off the shelf, but a skilled
optician can make them for you. Surgery can be done, but weakness
often comes back, making it necessary to repeat the operation.
Weak neck muscles can make it hard to sit up quickly
or lift one’s head straight up off a bed or couch. The stronger
trunk muscles have to be used for these actions.
Muscle weakness generally has a somewhat different
pattern in MMD2. Facial weakness is usually milder than in MMD1,
while weakness of the upper part of the leg (thigh) occurs early
in the disease, In type 1, thigh weakness, if it occurs, comes
late in the disease.
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Breathing and Swallowing Muscles
Respiratory muscles can become weak in MMD, affecting
lung function and depriving the body of needed oxygen. This is
probably at least part of the reason many people with MMD feel
sleepy much of the time.
The respiratory problems are further aggravated,
many experts believe, by an abnormality in the brain’s breathing
control center. This abnormality can also lead to a condition
known as sleep apnea, in which people stop breathing
for several seconds or even a minute many times a night while
they’re sleeping.
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The use
of a portable ventilator with a face mask during the night
can help compensate for weak breathing muscles and faulty
breathing control by the brain. |
A good way to treat respiratory muscle weakness
is with a small, portable ventilator that pumps air into the lungs
during the night. It’s usually used with a face mask that
can easily be taken on and off. (This kind of breathing assistance
can also be used during the day, but that’s usually not
convenient or necessary.)
Devices and techniques to assist with coughing
up secretions can be used, too, especially when the person with
MMD has a cold or chest infection. Your MDA clinic doctor, respiratory
therapist or a specialist called a pulmonologist can
help advise you about these devices and how to use them.
Swallowing muscles, if weakened, can lead to
choking, or “swallowing the wrong way,” with food
or liquid going down the trachea (windpipe) instead of the esophagus
(tube from the throat to the stomach). Swallowing is partly voluntary
and partly involuntary, and both sets of muscles can be affected.
Vomiting can be very dangerous for a person with
MMD whose swallowing muscles are weak. A head-down position is
crucial to prevent inhaling the vomit — a possibly fatal
problem.
A swallowing specialist can help people learn
to swallow more safely and, if needed, how to change the consistencies
of foods and liquids so they can be swallowed more easily. It’s
important to watch for swallowing problems, such as a tendency
to choke on food or drinks, and mention them to the doctor.
If swallowing difficulties are extreme (more common
in congenital MMD than in adults with MMD), a feeding tube can
be inserted into the stomach. It can later be removed if the problem
resolves itself.
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Myotonia
The myotonia of voluntary muscles can make it hard for someone with
MMD to relax the grip, especially in cold temperatures. Door handles,
cups and tools may pose a problem, although many people never notice
it.
Myotonia can affect other muscles, but usually it isn’t
noticeable. After sneezing, it can be hard to relax the muscles
around the eyes. This can pose a driving hazard. If myotonia becomes
troublesome, drugs can be used to treat it.
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Heart Problems
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A cardiac
pacemaker can return the heartbeat to a normal rhythm. |
The heart can be affected in adult MMD. Oddly,
since MMD is mostly a muscle disease, it isn’t the muscle
part of the heart (which pumps blood) that’s most affected,
but rather the part that sets the rate and rhythm of the heartbeat
— the heart’s conduction system. It’s
common in MMD, especially after many years, to develop a conduction
block, a block in the electricity-like signal that keeps
the heart beating at a safe rate.
Fainting, near fainting or dizzy spells are the
usual symptoms of conduction block, and these should never be
ignored! Such problems can be fatal.
In the early stages, a partial conduction block
may cause no symptoms but can be detected by an electrocardiogram
(EKG), a painless test of how the heart is beating. The doctor
will likely order regular EKGs. Conduction blocks can usually
be corrected by a cardiac pacemaker, an electronic device
that’s surgically inserted near the heart to regulate the
heartbeat.
Not everyone with MMD needs treatment for heart
problems, but everyone should be checked for them. Heart problems
are thought to be less common in type 2 MMD than in type 1.
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Internal Organs
Most of the internal organs in the body are hollow
tubes (such as the intestines) or sacs (such as the stomach).
The walls of these tubes and sacs contain involuntary muscles
that squeeze the organs and move things (food, liquids, a baby
during childbirth and so forth) through them.
In MMD, many of the involuntary muscles that surround
the hollow organs can weaken and can also have myotonia. These
include the muscles of the digestive tract, the uterus and the
blood vessels.
Abnormal action of the upper digestive tract can
impair swallowing. Once food is swallowed, the involuntary muscles
of the esophagus take over. These can have spasms and weakness,
causing a feeling of food getting “stuck” and sometimes
leading to inhaling food into the lungs. Care in swallowing, sometimes
with the advice of a specialist, may be needed.
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The digestive
tract and uterus (womb) are often affected in myotonic dystrophy.
These organs contain involuntary muscles, which can weaken
or develop myotonia (trouble relaxing). Abnormalities in
the brain can lead to excessive sleepiness or apathy. The
heart (especially the "electrical" part) can also
be affected. |
The lower digestive tract — large intestine
(colon), rectum and anus — can also be affected by weakness
and spasm in MMD. Crampy pain, constipation and diarrhea can occur.
Your doctor can advise you about setting up a bowel routine and
using diet and other treatments to help manage this kind of problem.
The gallbladder — a sac under the liver
that squeezes bile into the intestines after meals — can
weaken in MMD. People with MMD are probably more likely than the
general population to develop gallstones. Symptoms are difficulty
digesting fatty foods and pain in the upper right part of the
abdomen. Surgery can be done if necessary.
Drugs such as metoclopramide (Reglan) help move
things along the digestive tract and are sometimes used to treat
problems in this area in MMD.
Fortunately, most people don’t have problems
in urinating or holding onto urine in MMD.
Because of weakness and uncoordinated action of
the muscle wall of the uterus, women with MMD often have complications
in childbirth that can be serious for both mother and baby. These
may involve excessive bleeding or ineffective labor. Sometimes
a Caesarean section is advised, but surgery can also be a problem
in MMD (see "Anesthesia").
A pregnant woman with MMD has to be certain that
all her doctors, including any who will manage the delivery, are
well informed about her neuromuscular condition. Disasters can
result if this step is missing.
Blood pressure in MMD tends to be low. This is
probably due to low tone of the smooth muscles in the blood vessels.
It usually poses no problem and may even be one beneficial effect
in MMD.
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The Brain
Some people with type 1 MMD have been labeled by doctors and family
members as slow, dull, uncaring, unenthusiastic or depressed.
Only recently have researchers tried to get at the truth or untruth
of these descriptions.
First, as with other aspects of MMD, there’s a wide range
in severity of the mental and emotional symptoms of the disorder.
Some people function very well, others poorly, many somewhere
in between.
Children born with the severe, congenital form of MMD1 have a
lot of learning problems and may even be mentally retarded. They
often need special education because of these disabilities.
In adults, severe mental impairment is less common, but an overall
inability to “settle down to something,” apply oneself
to work or family life, concentrate or become engrossed in a task
is often reported in MMD1. MMD2 doesn't seem to involve these
sorts of problems, although there can be mild cognitive difficulties.
Adults with MMD1 often find they need much more sleep than do
other people and may feel at the beginning of the day the way
most people feel at the end of a long workday. This can be very
hard for others to understand.
Recent research suggests that, in MMD1, there may be abnormalities
in the parts of the brain that determine the rhythm of sleeping
and waking. Respiratory regulation and weakness of the respiratory
muscles, along with irregular breathing during sleep, all combine
to make this problem severe in some people (though not in everyone).
Weakness of the facial muscles, with drooping eyes, can add to
an outsider’s impression that the person with MMD1 is apathetic
or dull. Facial expression can be misleading in this disorder.
Facial weakness is mild in MMD2 and is less likely to confuse
observers.
Daytime sleepiness can sometimes be helped with medication. One
drug that can be used is methylphenidate (Ritalin). A newer drug
is modafinil (Provigil). These drugs may work on the brain's sleep-wake
cycle.
Another approach that can be tried is to coax the body into a
better rhythm of sleeping and waking by going to bed and getting
up at the same time every day no matter what the requirements
of the day may be.
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The Eyes
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The eye's lens focuses
light on the back part of the eye to allow vision. When
cataracts cloud the lens, the visual image is no longer
as clear. |
Cataracts — cloudy areas of the lens of
the eye that can eventually interfere with vision — are
extremely common in both types of MMD. Cataracts are caused by
a chemical change in the lens, which gradually goes from clear
to cloudy the way the clear part of an egg changes to white when
cooked. Exactly why cataracts occur in MMD isn’t known.
The person with a cataract may notice that things
start to look blurry, hazy or dim, and that this worsens gradually
over time. It often happens in both eyes but not necessarily at
the same time or at the same rate.
Surgery can remove a lens that contains a cataract.
Then, the surgeon either puts in an artificial lens, or the patient
can wear special contact lenses or eyeglasses.
Vision correction with cataract surgery is quite
good. However, with this operation or any procedure requiring
anesthesia, the medical team must be informed about the underlying
MMD. Anesthesia can pose special problems for the patient with
MMD (see below).
The muscles that move the eyes, as well as those
that open and close them, can also be affected in MMD, and other
eye problems can sometimes occur. Your primary care provider or
MDA clinic physician can refer you to an eye doctor (ophthalmologist)
when eye problems need attention or for regular checkups.
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Diabetes
If you read about MMD in books or on the Internet, you may find
diabetes listed among the problems in this disorder.
Fortunately, most people with MMD don’t have severe diabetes,
but they may develop a mild type sometimes referred to as insulin
resistance with high blood sugar. This means the body makes
insulin (a hormone needed for the cells to take up and use sugars),
but for some reason, the insulin isn’t quite doing its job.
Your doctor may order blood and/or urine tests to see if you
have insulin resistance or diabetes. If you do, you may be advised
to change your diet or exercise habits or to take medication.
Your doctor may refer you to a specialist or primary care physician
for further treatment for diabetes.
High blood sugar affects a minority of people with MMD2.
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Anesthesia
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If you're
planning surgery, be sure the neurologist, anesthesiologist
and surgeon know you have myotonic dystrophy. |
An unusually high rate of complications and even
deaths associated with general anesthesia (given during any surgery)
have been reported in people with MMD. This can occur even if
the MMD is mild. In fact, these cases can be particularly dangerous,
because the surgeon, anesthesiologist and patient may be less
likely to pay attention to the MMD when planning surgery.
Surgery can usually be safely undertaken with
careful monitoring of cardiac and respiratory functions before,
during and after the surgery. Be sure to tell the entire medical
team, especially those responsible for the anesthesia, that you
or your family member has MMD. Have the anesthesiologist and the
neurologist communicate long before the surgery if at all possible.
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What Happens
In Congenital MMD?
The most serious form of MMD is the congenital
(at birth) form of the disease. Congenital MMD has only been observed
in MMD type 1. When a child with congenital MMD is born, it’s
almost always found that the mother has adult-onset MMD —
even though her symptoms may be so mild that she doesn’t
even know she has the disorder.
Mothers with MMD can also pass on the adult-onset
form. A child can also inherit the disease from the father, but
it’s almost always the adult-onset form. These unusual features
aren’t seen in other genetic disorders.
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Weak Muscles
Babies with congenital MMD have very weak muscles
and a lack of muscle tone (hypotonia). They appear floppy,
have trouble breathing, and suck and swallow poorly.
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| A child born with congenital myotonic
dystrophy is likely to have facial weakness and an upper lip
that looks "tented." The eye muscles may also be
affected. |
In the past, many of these infants didn’t
survive. Today, with special care in neonatal intensive care units,
such children have a much better chance of survival, but they
enter childhood with multiple problems.
Respiratory support, such as artificial ventilation,
will probably be needed, at least at first. Voluntary and involuntary
aspects of respiration are probably affected in congenital MMD.
Because swallowing muscles are affected, special feeding techniques
or a feeding tube that goes into the stomach may be needed to
provide adequate nutrition and prevent choking.
Children with congenital MMD have severe facial
weakness, leading to a lack of facial expression and an upper
lip that comes to a point — known as a tented upper
lip.
Babies with congenital MMD are often born with clubfeet — a curvature of the feet and lower legs.
Clubfeet need surgical correction for the child to be able to
walk. The problem may be due to abnormal muscle development in
the lower legs and feet during fetal life.
Infants with MMD don’t have myotonia.
If they survive, however, they’ll develop it later in life.
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Mental Retardation
Infants born with congenital MMD are likely to
be mentally retarded, although this isn’t always the case.
This seems to be related to maldevelopment of parts of the brain,
presumably caused by genetic abnormalities.
Some experts have suggested that the very high
incidence of labor and delivery complications in mothers with
MMD could also be a contributing factor to the mental problems
seen in these babies. For this reason, it’s very important
to make doubly sure that everyone on the medical team is aware
of and can work to minimize the risks surrounding labor and delivery
to the mother and child with MMD.
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Speech and Hearing Difficulties
The muscles involved in talking are often affected
in congenital MMD. Hearing can also be impaired.
Therapy from a speech-language pathologist (in a medical center) or speech therapist (in a school)
can help. Even before a child enters school, early intervention
programs are vital. Talk to your pediatrician, MDA clinic physician
or medical social worker about such programs.
Vision Problems
The eye muscles are affected and can cause the
eyes not to work together; this condition is called strabismus.
If severe, it can be corrected with surgery.
Cataracts, common in adult-onset MMD, aren’t a feature of congenital MMD during early childhood. However, children
with MMD are likely to develop them later.
Outgrowing Congenital MMD
Infants and children with MMD symptoms may “outgrow”
many of the muscle-related aspects of the disorder as they mature.
The mental retardation doesn’t improve, but these children
can learn if given the right tools and environment.
Unfortunately, despite early gains during childhood,
all children with congenital MMD go on to develop the adult form
of MMD when they reach adolescence or adulthood.
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How is MMD
Diagnosed?
Doctors who have experience with neuromuscular
disorders find it easy to diagnose type 1 MMD. They can usually
just look at a person, examine him and ask a few questions to
make the diagnosis. Teen-agers and adults with MMD usually have
a characteristic long face with hollow temples and, in men, early
balding.
Many people tell the doctor about recurring abdominal
pain, constipation or obstetrical complications. Others say their
parents had some muscle problems.
Sometimes, an eye doctor will notice the particular
type of cataract found in MMD and suspect the diagnosis, referring
the patient to a neurologist.
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Children with congenital myotonic muscular dystrophy enter the world with many problems. Early physical, occupational and speech therapy can help them make the most of their abilities. |
Many people may not realize they have any trouble
relaxing their grip, but others say they’ve had trouble
letting go of a shovel, screwdriver or some other device, especially
in cold weather.
The doctor may check for myotonia by lightly tapping
the area just under the thumb with a rubber hammer. In most people,
there is little or no response. In people with myotonia, there’s
a swift contraction of the muscle, which takes several seconds
to relax.
The doctor may want to do electrical testing of
the muscles and nerves, using an electromyogram, or EMG.
In this exam, small needles are inserted into muscles to measure
their electrical activity.
In a few cases, a muscle biopsy may be
considered. In this test, a small piece of muscle is surgically
removed for examination.
The doctor may move from the history and physical
exam to a DNA test to confirm a diagnosis of MMD. The DNA test
involves only a blood sample and, in almost all cases, can determine
whether the family is affected by MMD.
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How is MMD Treated?
At this time, there’s no specific treatment
that “gets at the root” of MMD. Treatment is aimed
at managing symptoms and minimizing disability.
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| A cane can provide support when lower
leg weakness makes walking hazardous. |
Canes, braces, walkers and scooters can help with
mobility problems. Careful monitoring of cardiac and respiratory
functions can lead to early treatment of these problems with a
cardiac pacemaker or a portable ventilator.
Medications and other treatments for constipation
and other digestive tract complaints can be employed. Surgery
for cataracts and either surgery or special eye crutches for drooping
eyelids can markedly improve vision. New medications to treat
excessive sleepiness can make life more enjoyable for the person
with MMD and his or her family.
In children with the congenital form of MMD, early
intervention is crucial. Hearing and vision abnormalities should
be diagnosed and treated as soon as possible. Surgery for uncoordinated
eye muscles and special education are among the interventions
that can greatly influence a child’s later success in life.
If you have a child with congenital MMD, it’s
very important to seek out an early intervention program through
your MDA clinic, pediatrician, medical social worker, school system
or other resources.
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Facts About Myotonic Muscular Dystrophy
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