Duchenne muscular dystrophy (DMD) was first described by the French
neurologist Guillaume Benjamin Amand Duchenne in the 1860s. DMD is due to
a mutation on the X-chromosome, which means it is an inherited X-linked
trait. As a result, only boys are usually affected. The deletion of the
dystrophin gene causes a lack of production of dystrophin. Dystrophin is
a protein associated with the membrane surrounding each muscle fibre. In
common terms, it acts like a glue to hold the muscle together. The gene
is 2.5Mb in Xp21.
DMD boys appear normal at birth. Therefore, the onset of DMD is often
ill defined. One of the first signs is enlarged calf muscles. Boys with
DMD usually fall more often, are never able to run well, and have
difficulty climbing stairs. They often walk on the toes with the abdomen
pushed forward causing a waddling gait. This comes about from a weakness
of muscles of the pelvis.
Getting up from a seated position on the floor becomes increasingly
difficult. To compensate, boys use what is referred to as the Gower's
method of rising. From a position on all fours, the boys presses on his
thighs and climbs up them on order to extend the hips and then to a
standing position.
Weakness of the shoulder muscles also increases, which makes it
increasingly difficult to raise their arms. The heal cord begins to
tighten up, also making walking more difficult. Due to all this, most
boys become wheelchair bound by the age of 12. Once chair bound,
scoliosis, curving of the spine, becomes a problem. Scoliosis is a
serious problem because it results in compression of the lung. This in
turn affects breathing and predisposes to chest infections. To limit the
progression of scoliosis, there is a surgery that attaches rods to the
spine.
There are basically three tests for diagnosis of DMD. The first is a
blood test for the muscle enzyme creatine phosphokinease (CPK). In
healthy persons, the CPK level is normally ranges from 100 to 200.
However, in DMD CPK is elevated by 50 to over 100 times the normal level.
A DNA test can be conducted to attempt to find a deletion in the
dystrophin gene. Finally, a muscle biopsy is taken to test muscle tissue
for the absence of dystrophin.
At the suggestion of a doctor, we had Matt's blood test to determine
his CPK level. His test came back with a level of 19,800 !! The world
seem to come crashing down on our family on the day the test came back.
Diagnosis was DMD. To be sure, we had the muscle biopsy done. This test
showed that all fibers were negative for dystrophin. His DNA test did not
find a deletion. Based on these tests, it was confirmed that Matt has
DMD.
There is currently no known cure for DMD. As you would imagine, we are
very interested in DMD research and finding a cure. Presently the current
research is focused on gene therapy, myoblast transfer, and drug therapy.
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