Duchenne
Muscular Dystrophy
English Links:
www.parentprojectmd.org
Dutch Links:
www.duchenne.nl
www.vsn.nl
All forms of Muscular Dystrophy are considered rare, but
Duchenne Muscular Dystrophy is perhaps the most common of
the Muscular Dystrophies in existence. Since it was first
identified in the 1860's, Duchenne MD affects approximately
1 boy in every 3,000.
Who gets Duchenne MD Duchenne MD is not specific to any one
group. All ethnic groups are equally susceptible to both
Duchenne and Becker MD. But what often sets these two
Muscular Dystrophies apart is that they occur mainly in
boys (with very few exceptions), making it a sex-linked
disorder.
Because boys have one X-chromosome and one Y-chromosome,
and girls have two X-chromosomes, boys are always at a
greater risk of inheriting disorders caused by damaged
genes on the X-chromosome. To put it simply, if something
is wrong with a gene on a boy's X-chromosome, his body has
no other way to recreate a fully functional version of that
damaged gene. Girls are fortunate to have an "extra"
X-chromosome to fall back on if one of their genes are
damaged.
What causes Duchenne MD Within our gene makeup, there is an
important muscle protein called 'dystrophin' which is one
of the largest genes found to date. Dystrophin acts as the
glue that holds muscles together by maintaining the
structure of muscle cells. Dystrophin is also believed to
carry signals between the inside and outside of muscle
fibers. Without dystrophin, muscles are not able to operate
properly and will eventually suffer progressive damage.
The dystrophin gene is carried on the X-chromosome. Boys
are therefore more susceptible to dystrophin damage because
they have only one X-chromosome. When a boy is diagnosed
with Duchenne MD, his body is not able to produce any
dystrophin. In Becker MD, a distorted, over-sized version
of dystrophin is generated. In either disorder, muscle
cells within the body gradually weaken and eventually die,
without fully functional dystrophin.
Early
Phase (diagnosis through age 7)
Once a boy is diagnosed with DMD, it is often quite
difficult to accept or believe that there is anything wrong
with him. The onset of physical symptoms may be tough to
recognize. Often times he will appear to be improving on
the outside while his muscles are deteriorating on the
inside. It is during this early phase that the calves may
seem overdeveloped. He may appear clumsy and fall a lot.
Jumping from a standing position may become near
impossible.
Transitional
Phase (6-12 years)
Between the ages of 6 and 12, DMD has usually been
diagnosed. The child will likely have trouble walking,
mostly because his quadriceps (muscles in the front of the
thighs) have grown weaker. This tends to keep him off
balance as he attempts to shift his weight and walk. He may
walk on the balls of his feet or on his toes with a slight,
rolling gait. In order to compensate for a feeling of
falling forward, young men with DMD will stick their
bellies out and throw their shoulders back to keep their
balance as they walk.
When asked to get up off of the floor, he will often put
his rear end up in the air first and then "walk" his arms
up his legs with his hands until he is standing; using his
arms for supports. The medical term for this is 'Gowers'
Maneuver.'
Loss of
ambulation (8-14 years)
By about 12 years old, he will likely need a wheelchair for
at least part of the time as mobility becomes more
difficult. His weakened muscles will cause him to tire
easily. In most cases teen years are when the most
significant loss of skeletal muscle strength takes place.
It is at this point that activities involving the arms,
legs, or trunk of the body will require assistance or
mechanical support. Most young men will retain the use of
their fingers through this phase so they can generally
still write and use a computer.
Adult
Stage (15+ years)
During the teen years, in addition to skeletal muscle
problems, young men with DMD will often develop heart
muscle problems. Heart complications become the main threat
to both health and life due to damage and loss of
respiratory muscle. The muscle layer of the heart (called
'myocardium') begins to deteriorate, much like the skeletal
muscles do. This puts the young men at risk of a heart
attack. Major symptoms of myocardium include: shortness of
breath, fluid in the lungs, or swelling in the feet and
lower legs (caused by fluid retention).
When symptoms of DMD are managed conventionally, young men
with the disorder usually die from respiratory failure
before they turn 25. It has been estimated that anywhere
from 9% to 50% of those with DMD die from cardiac failure.