MDF Magazine Newsletter Issue 57 December 2018

MD
Some facts about Duchenne and Becker
muscular dystrophy
What is Duchenne/Becker muscular
dystrophy?
Duchenne muscular dystrophy (DMD) is the most common
and serious neuromuscular genetic disorder diagnosed in
childhood. It is a progressive disorder that causes muscles
to become weaker over time until it affects the whole body.
DMD mostly affects boys and reaches across all races and
cultures. Although genetic disorders are usually passed down
from a parent to a child, Duchenne and Becker muscular
dystrophy (BMD) can spontaneously occur even if no one in
the family has had it before.
Becker muscular dystrophy occurs when dystrophin is
manufactured, although not in the normal form or amount.
Because of this, people with Becker are more mildly affected
and have a slower progression than people with Duchenne.
As with Duchenne, Becker can be inherited from a parent
or can be caused by a new or spontaneous mutation in the
dystrophin gene. The symptoms of Becker can begin in
childhood, the teenage years, or even later. PPMD’s
mission and work extends to both Duchenne and Becker (both
considered ‘dystrophinopathies’), but for simplicity we
primarily refer to Duchenne.
DMD is a “gender-linked or “X-linked” disorder. Males are
born with one X-chromosome (from mom) and one Y-chromosome
(from dad). Because males only have one X chromosome,
if the X-chromosome they receive has a gene mutation
that causes Duchenne, the male will be born with Duchenne.
Females are born with two X-chromosomes (one from mom
and one from dad). If females have one X-chromosome that
has a gene mutation for Duchenne, the body will generally
choose to “activate” the other normal X chromosome. If
this happens, the female will be a carrier of Duchenne. This
means that she can pass Duchenne on to her sons (her daughters
can also be carriers) but she herself will have few, if any,
symptoms of Duchenne. If the female’s body, for whatever
reason, chooses to activate the X chromosome with the mutation
for Duchenne, the female will still be a Duchenne carrier,
but will also “manifest” symptoms of Duchenne. She
will then be a “manifesting carrier” of Duchenne.
What causes the symptoms?
Parent Project Muscular Dystrophy writes as follows
(©2018):
Duchenne is caused by mutations in the gene that encodes
for a muscle protein called dystrophin. Dystrophin is in
every single muscle fibre in our bodies. Dystrophin acts as
the glue that holds muscles together and the “shock absorber”
that allows muscles to contract and relax without being
damaged. Without dystrophin, muscles are not able to function
or repair themselves properly. As muscles are used for normal
day-to-day activity, tiny tears are created in the muscle.
Because there is no dystrophin, the muscles can’t repair
themselves by making new muscle, so the damaged muscle
is replaced by fat and scar tissue. As muscle is replaced, the
person with Duchenne loses muscle function and strength.
There are many muscles in the body (skeletal muscles, heart
muscles, breathing muscles, etc.). Because there are so many
muscles in the body, many parts of the body can be affected
by Duchenne. For that reason, people living with Duchenne
need care for many areas of the body.
What are the symptoms of DMD and which
muscles are affected?
The DMD fact sheet of the Muscular Dystrophy Foundation
of South Africa (2000b) provides the following information:
Most affected boys develop the first sign, which is difficulty
in walking, at the age of 1 to 3 years. By approximately 8 to
11 years they become unable to walk. By their late teens to
early twenties the weakness is usually serious enough to put
their lives at risk.
Boys affected by DMD often walk on their toes with their
abdomen pushed forwards and with a waddling gait. This
is due to weakness of pelvic muscles, which normally
extend to the hips in order to retain the upright position when
standing. When these muscles are weak there is a tendency
for the pelvis to tilt forward, and to compensate for this the
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