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Muscular Dystrophy FAQs
WHAT IS MUSCULAR DYSTROPHY?
Muscular Dystrophy (MD) is the name of a group of muscle disorders that are characterized
by progressive weakness and wasting of the voluntary muscles that control body movement.
As muscle tissue weakens and wastes away, it is replaced by fatty and connective tissue.
WHO CAN BE AFFECTED BY MUSCULAR DYSTROPHY?
Anyone can be affected. Contrary to popular belief, muscular dystrophy is not
exclusively a childhood disorder. While some types of MD are first evident in infancy or
early childhood, other types may not appear until later in life.
HOW DO THE VARIOUS TYPES OF MUSCULAR DYSTROPHY DIFFER?
Specific disorders within this group vary in many ways. Which muscles are chiefly involved
is different from disorder to disorder. The severity of the symptoms, the age at which the
symptoms appear, how fast the symptoms progress and what pattern of inheritance the
disorder follows are all factors which differ between the various forms of muscular
dystrophy.
IS MUSCULAR DYSTROPHY ANYONE'S FAULT?
No. Muscular dystrophies are genetic diseases. Forms of muscular dystrophy can be passed
on from generation to generation, or they can occur spontaneously in a single individual
as the result of a mutation of a particular gene. In any case, they are not anyone's
fault.
IS MUSCULAR DYSTROPHY CONTAGIOUS?
No. Genetic diseases are not contagious.
WHAT CAUSES MUSCULAR DYSTROPHY?
Each form of muscular dystrophy is caused by an error in a specific gene associated
with muscle function.
WHAT ARE GENES?
Genes are the basic functional units of heredity that let the cells and tissue of
the body know what specialized functions they will perform. There are approximately 80,000
individual genes located on the 46 chromosomes inside each cell within the human
body.
HOW DO GENES FUNCTION?
Genes are the blueprints for body structure and function. Each gene carries the code
required to direct the cell to make a specific protein. Proteins are the molecules that
carry out all of the work of the cell. The proteins synthesized b the genes are
responsible for all structure and functions of living cells from eye colour to muscle
function. They also form part of hormones and are components of enzymes within the body.
HOW DO GENE ABNORMALITIES CAUSE MUSCULAR DYSTROPHY?
Muscle tissue is made up of long muscle fibres. Each fibre is actually an elongated
cell that is made up of many individual cells that have fused. The genes in the nuclei of
these cells direct the production of the proteins that carry out the function of muscle
tissue (muscle contraction). Different types of muscular dystrophy are due to errors in
different proteins, determined by different genes. Lack of dystrophin causes breakdown of
muscle fibres that leads to a specific clinical pattern that has been called Duchenne
muscular dystrophy. Becker muscular dystrophy is another muscular dystrophy where there is
insufficient production of dystrophin, but to a less severe degree (dystrophin is still
produced but it is either altered or available in abnormally low amounts). The clinical
picture is closely related to Duchenne, but symptoms are less severe and progression of
weakness is slower.
WHERE DO THE FAULTY GENES COME FROM?
When a baby is formed, he/she receives 23 chromosomes from each parent, for
otal of 46 chromosomes (23 pairs). Normally, each pair of
chromosomes carries genes for the same trait. 22 pairs of the chromosomes are called
autosomal chromosomes, which simply means that they are identical in both males and
females. The 23rd chromosomal pair is known as the sex chromosome, and it is here that the
sex of the unborn child is determined. Each female carries two X chromosomes and each
males carries one X and one Y chromosome. An unborn child will receive one X chromosome
from the mother and either an X or a Y from the father. If an X is received from each
parent, the child will be a girl (XX). If a Y is received from the father, then the child
will be a boy (XY). Genes are found packed together on these chromosomes. Each gene has a
precise location on one of them. For reasons that are only partly understood, one or more
genes may become flawed or lost, and a serious disorder may result. Depending on the type
of muscular dystrophy, the faulty or missing genes may be inherited. Also, the way that
the disorder is inherited will vary from disease to disease. There are three main patterns
of inheritance: autosomal dominant and autosomal recessive, which relate to transmission
of traits determined by genes on the autosomal chromosomes, and X-linked recessive, which
pertains to traits determined by genes found on the X chromosomes.
WHAT IS AUTOSOMAL DOMINANT INHERITANCE?
Disorders that follow an autosomal dominant inheritance pattern typically appear in
every generation, without skips. Autosomal refers to the fact that the genetic error can
occur on any one of the 46 chromosomes in each cell in the human body, except the two sex
chromosomes. Dominant refers to the fact that it is necessary for only one parent to
transmit the abnormal gene for the disorder to be transmitted. The other parent transmits
a normal gene. Thus, the disorder can be inherited from either parent and each child of an
affected parent has a 50% chance of being affected. The severity of the disorder and the
age of onset can vary from person to person. Examples of disorders with this type of
inheritance pattern are facioscapulohumeral dystrophy and myotonic dystrophy.
WHAT IS AUTOSOMAL RECESSIVE
INHERITANCE?
In autosomal recessive inheritance, the disorder usually appears in only one
generation, and there is typically no previous family history of the disorder. Both
parents must be carriers of the faulty gene. A carrier harbours the faulty gene, but
usually show no symptoms. Recessive refers to the fact that the child needs to inherit the
faulty gene from both parents in order to have the disease. Children of either sex can be
affected. With each pregnancy, there is a 25% chance the child will receive a faulty
gene from each parent and thus, will be affected with the disorder. If the child inherits
a faulty gene from one parent only, he/she will be a carrier of the disorder, but will
probably show no symptoms. There is a 50% chance the child will be a carrier. An example
of an autosomal recessivel inherited form of muscular dystrophy is limb-girdle
muscular dystrophy.
WHAT IS X-LINKED RECESSIVE INHERITANCE?
In an X-linked mode of transmission, the faulty gene is carried on one of the X
chromosomes that helps determine the sex of a child. The disorder is passed on to male
children by their mothers. When the mother is a carrier, boys have a 50% chance of being
affected, while girls have a 50% chance of being carriers. Should a man with an X-linked
dystrophy have children, none of his sons will be affected, while all of his daughters
will be carriers. This is because his sons receive the Y chromosome, which is normal, and
his daughters receive th affecte X chromosome. Examples of X-linked recessive
inherited forms of muscular dystrophy are Duchenne and Becker muscular dystrophy.
WHAT IS A GENE MUTATION?
A gene mutation is a spontaneous or
inherited change in a gene that allows an altered characteristic or disorder to appear.
New gene mutations are unpredictable, occurring at random within the population. It has
been shown that in approximately one third of boys with Duchenne muscular dystrophy, the
disease appears as a result of a spontaneous gene mutation. In fact, gene mutations are
not uncommon in some other serious early onset forms of Muscula Dystrophy passed on
via autosomal dominant or X-linked inheritance pattern.
WHAT ARE SOME OF THE SPECIFIC TYPES OF
MUSCULAR DYSTROPHY?
Duchenne M.D.
Becker M.D.
Myotonic M.D. (Steinert's Disease
Congenital M.D.
Limb-Girdle M.D.
Facioscapulohumeral M.D.
(FSH)
Becker Muscular Dystrophy
Type of inheritance: The genetic transmission of the disorder is X-linked recessive. It is
caused by mutations in the same gene as DMD.
Clinical Onset: The onset of symptoms is generally later in BMD than in DMD, and can occur
anywhere from 5 years of age to young adulthood. As in DMD, in families where there is a
positive history of muscular dystrophy, BMD can be detected or ruled out in infants by
means of a blood test.
Initial Symptoms: Again, initial symptoms are similar to Duchenne, only milder in
severity.
Progression: The rate of progression is slow. Many people with Becker muscular dystrophy
are able to walk well into their teens and adult years. Life expectancy is, in many cases,
normal.
Limb-Girdle Muscular Dystrophy
Type of Inheritance: This is a group of inherited forms of muscular dystrophy. Most are
autosomal recessive, but some forms of limb-girdle muscular dystroph follow a
dominant pattern of inheritance.
Clinical Onset: The onset of symptoms is extremely variable, becoming evident anywhere
from early childhood to adulthood. Usually, affected members of a family have about the
same age of onset and degree of severity.
Initial Symptoms: Some forms of limb-girdle
MD affect the lower extremities initially. Symptoms include difficulty with gait, running,
climbing stairs and risin from the floor. Other forms affect the shoulder muscles
predominantly with resulting difficulty in lifting the arms.
Progression : Progression of limb-girdle muscular dystrophy is variable. In som
cases, it progresses very slowly, while in others, progression is rapid. Life span is
often unaffected.
Facioscapulohumeral
Muscular Dystrophy (FSH)
Type of Inheritance
FSH is an autosomal dominant type of muscular dystrophy. The gene for the most common type
of FSH is located on chromosome 4.
Clinical Onset: This disorder generally appears when a person is in early adolescence, but
it can also appear in young adulthood or childhood. It can usually be detected earlier by
clinical examination in a family where there is a positive family history.
Initial Symptoms: Lack of facial mobility (smiling, whistling), difficulty in raising arms
over the head and forward slope of the shoulders are some of the common initial symptoms.
Progression: The progression of facioscapulohumeral muscular dystrophy is typically slow,
with long periods of time when the disorder seems to stop progressing altogether. As the
trunk and leg muscles become involved, persons with this disorder may lose their ability
to walk. Life span is often normal.
ARE THERE ANY OTHER FORMS OF MUSCULAR
DYSTROPHY?
There are a number of other forms of muscular dystrophy: They include: Distal
muscular dystrophy, Emery-Dreifuss muscular dystrophy, Fukuyama congenital muscular
dystrophy, Oculopharyngeal muscular dystrophy, Ophthalmoplegic muscular dystrophy, These
and other forms of neuromuscular disease can be diagnosed by a physician, utilizing the
tests described in this brochure. Additional information on any of these forms
of muscular dystrophy can be obtained from Client Services staff in the office nearest
you.
HOW IS MUSCULAR DYSTROPHY DIAGNOSED?
A diagnosis of muscular dystrophy is made by a physician. A family history and a
complete physical examination may provide answers about the muscle weakness that an
individual is experiencing. Also, a doctor can provide advice about the progression of a
patient's symptoms. In addition, diagnostic tests are used by the physician to
aid in determining whether or not a person has muscular dystrophy and which form of the
disease he/she has.
WHAT DIAGNOSTIC TESTS MAY BE PERFORMED?
1.Blood tests are used regularly to aid in diagnosis. For example, one test may be
done to measure the level of certain enzymes in the blood. As muscle breaks down, these
enzymes, especially creatine kinase (CK or CPK), are leaked into the blood stream and the
resulting elevated levels are useful in determining a correct diagnosis. Using blood
samples, DNA testing may also be performed. Here, the genetic material (DNA) may also be
studied in some muscular dystrophies for disease diagnosis and carrier testing. 2.An
electromyogram is a procedure in which small electrodes are placed into a muscle. This
test may reveal electrical activity patterns that are characteristic of muscular
dystrophy. 3.A muscle biopsy is one test that is commonly performed. With this
test, doctors surgically remove a small piece of muscle tissue and examine it under a
microscope. In addition, special staining for the specific protein normally produced by
the gene of interest (e.g. dystrophin protein staining in Duchenne/Becker muscular
dystrophy) can now be performed for some of the muscular dystrophies.
WHERE CAN ADVICE BE OBTAINED?
Neurologists, doctors who specialize in disorders affecting the nervous system, are
often consulted for patients who may have a neuromuscular disorder. Nerves and muscles are
part of the so-called peripheral nervous system. Neuromuscular clinics and
hospitals across Canada are equipped to do the necessary diagnostic testing and to offer
advice and support about the management of muscular dystrophy. Geneticists,
doctors who specialize in medical genetics, molecular geneticists and genetic counsellors
are found in major cities in Canada and are available to patients and their families for
the purpose of diagnosis and counselling. A geneticist or a genetic counsellor may also be
able to determine the probability of the disorder reappearing in that family, and family
members can be advised about their risk of having an affected child. Client Services staff
in any of the regional offices of the Muscular Dystrophy Association of Canada are
available to assist clients in dealing with medical, emotional and social issues, as well
as to provide referrals to alternative resources.
WHAT TREATMENT IS AVAILABLE?
Although there is no cure for muscular dystrophy as yet, physiotherapy and
occupational therapy can help people with muscular dystrophy achieve their maximum level
of independence in daily living routines. In some cases, certain surgical procedures can
also improve the quality of life for many individuals with muscular dystrophy. What
can Physiotherapy Do? Physiotherapists are skilled in the physical and therapeutic
techniques commonly used to maintain strength and maximize range of motion, posture and
comfort in clients with muscular dystrophy. Muscle weakness can lead to
contractures, or abnormal shortening of muscle tissue. For example, in the early stages of
Duchenne muscular dystrophy, a young boy may have to walk on the tips of his toes because
of shortening of the tendon (heel cord) secondary to muscle breakdown and fibrosis in calf
muscles. This makes it difficult or impossible to straighten his foot. A daily routine of
stretching these weakened muscles can help delay the deformities sometimes caused by the
resulting contractures. A physiotherapist is the person who can teach family members to
perform these exercises. It is very important to determine the best level of
active and passive exercise that will maintain strength for as long as possible and
prevent contractures. The physiotherapist helps clients develop individual exercise
programs that include the type and amount of activity that is best for them.
What can Occupational Therapy Do?
Occupational therapists can help clients learn how to compensate for physical limitations
and learn to adapt to a new level of achievement in their daily living. For example,
occupational therapists help to determine appropriate equipment and seating needs for
clients as their disorder progresses. A client might be assessed by the therapist for such
things as a wheelchair, seating systems, or a computer to aid with writing. The therapist
can then teach the client how to use these devices that will enable him/her to continue to
participate as fully as possible at home, school, work and recreational activities.
What Types of Surgery can be Performed?
In cases where weakened muscles have caused, or are likely to cause, contractures, tendons
can be surgically severed. This procedure, called a tendon release, will relieve
developing contractures. The tendons known as "heel cords" (connecting a large
muscle at the back of the calf with the ankle joint), are a common site of surgery.
Clients with more severe contractures in the
knees and hips may benefit from tendon releases in those joints as well. This surgery is
often followed by casts, and then braces and physiotherapy to help maintain the improved
range of motion. Spinal curvature, or scoliosis, can also be surgically
corrected by an orthopedic surgeon. In Duchenne muscular dystrophy, for example, scoliosis
usually develops after a child has begun using a wheelchair, and back weakness and
imbalance rapidly progress. A surgical procedure to address this problem is often able to
correct the scoliosis and thus improve posture and breathing. Some examples of surgery for
scoliosis include a Luque procedure and spinal fusion. Opacities of the lens of the
eye, or cataracts, are often found in people with myotonic dystrophy. They can be
surgically removed by an ophthalmologist, and can thus improve a person's ability to see.
THE MUSCULAR DYSTROPHY ASSOCIATION OF CANADA
The purpose of the Client Services program of the Muscular Dystrophy Association of
Canada is to work in partnership with persons affected by neuromuscular disorders to
contribute to their quality of life. We are committed to: Empowering individuals through
provision of knowledge, resources and emotional support; Mobilizing resources in the
support community through education, coordination and advocacy; Providing
direct assistance. To this end, a number of services are available to clients across the
country who are registered with MDAC.
WHAT SERVICES DOES MDAC PROVIDE TO PEOPLE WITH MUSCULAR DYSTROPHY?
Information & Education: Our regional staff provides information about muscular
dystrophy, other neuromuscular disorders and related issues to clients and their families,
professionals and the general public. We also publish a national newsmagazine,
Connections. Equipment Program: Some funding assistance is available through MDAC for
basic medical equipment. Client Services staff will help clients locate additional sources
of funding where necessary. Support: MDAC supports a network of chapters and support
groups across the country where those with various forms of neuromuscular disease, their
families and friends, firefighters and any other interested parties get together for the
purpose of support, education, fundraising and social events. Travel: Some
assistance is available for airline travel to disorder-related medical appointments.
Referral: Regional staff provides a liaison with neuromuscular clinics and
referrals to other resources in the community for assistance with specific needs that
clients and family members may have.
Advocacy: Assistance is available to clients
in resolving individual problems. Client Services staff are also active in dealing with
community issues.
WHAT ABOUT RESEARCH?
The Muscular Dystrophy Association of Canada is committed to discovering a cure for
muscular dystrophy and other related neuromuscular disorders. MDAC funds research projects
in major medical centres across Canada. MDAC-sponsored researchers are considered among
the
world leaders in their field and are making significant progress in the fight against
muscular dystrophy. In 1986, Canadian scientists shared in the discovery of the gene for
Duchenne muscular dystrophy. Following this advance scientists discovered that a protein,
called dystrophin, was missing in the cells of these boys. Research into this disorder and
other neuromuscular disorders has been moving ahead since that time. These discoveries
have led to accurate diagnosis, carrier detection and prenatal diagnosis of Duchenne and
Becker muscular dystrophy and the search for a cure or an effective treatment is ongoing.
In addition: The exact nature and location of the gene causing myotonic
muscular dystrophy has been found, and the faulty protein has been determined. A group of
Canadian scientists were major contributors to this work. The faulty segment of
chromosome 4, which is responsible for the most common form of facioscapulohumeral
muscular dystrophy, has been identified. Since 1995, at least 11 different forms of
limb-girdle muscular dystrophy have been identified, each arising from a different genetic
error. The classification of the forms of limb-girdle muscular dystrophy is ongoing and
Canadian researchers, sponsored by MDAC are a large part of this process. Many of the
genes have been identified along with the protein that is missing or altered and
researchers continue to look for the rest. And Finally... Individuals are encouraged to
contact their MDAC regional office to discuss their needs and to get further information
about the disorders under our umbrella, the services that we provide and the various
research projects happening across Canada and around the world.
Compiled by:
Linda Wilton, R.N., B.Ed.,
Director of Client Services,
Muscular Dystrophy
Association of Canada, Prairie
Region
Reviewed by:
Cheryl R. Greenberg, MD, CM,
FRCP( C ), Director of
Metabolic Service, Section of
Genetics & Metabolism,
Children's Hospital, Health
Sciences Centre, Winnipeg,
Manitoba.
Pierre Jacob, M.D., F.R.C.P.(
C ), Neurologist, Children's
Hospital of Eastern Ontario,
Ottawa, Ontario.
Margaret Thompson, Ph.D.,
F.C.C.M.G., Professor
Emeritus, University of Toronto;
Editor, Connections Magazine.
Published by:
The Muscular Dystrophy
Association of Canada
2345 Yonge Street, Suite #900
Toronto, Ontario
M4P 2E5
Telephone: 1 (416) 488-0030
Toll-Free: 1 (800) 567-2873
Fax: 1 (416) 488-7523
MDAC Website: www.mdac.ca
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