In this video,
we hope to provide you with a better understanding of
muscular diseases.
Specifically,
Duchenne and Becker muscular dystrophy.
We will start off by addressing Muscular Dystrophy and the
associated mutations.
We will then proceed to address Duchenne and Becker muscular
dystrophy,
including its discovery, symptoms and diagnosis,
as well as prevention and treatment.
We will end off by providing a meaningful comparison between the
genetic and cellular mechanism of Duchenne and Becker muscular dystrophy.
This is particularly important because although both conditions are extremely
similar.
There are differences that can allow for an early diagnosis.
leading to the implementation of prevention strategies sooner rather than later to maximize
the quality of life. We will be starting off by providing a general overview of
muscular dystrophy.
Every cell in our body is coded for by special
instructions called genes. Together,
these genes make up our DNA.
Our body works
hard and playing various proofreading mechanisms to ensure that the
right instructions are used to create cells that function properly.
However,
this is not a perfect system. Instances where points
at the instructions are changed
are called mutations. Mutations
can range from harmless to very severe.
We would like to highlight two types of mutations; deletions
and duplications. Deletions occur.
when a part of the genetic code is missing,
while duplications occur when extra sequences at the genetic
code are added.
Muscular dystrophy is a class of conditions caused by genetic mutations.
This class is characterized by progressive muscle weakness,
and loss of muscle mass. Over time,
this decreases mobility, makes it difficult to complete everyday tasks
and can lead to deformity. There
are nine types of muscular dystrophies, each affecting different areas
or combinations of areas in the body.
The ones we will be discussing today are Duchenne and
Becker muscular dystrophy.
Moving on,
let's start to discuss Duchenne muscular dystrophy, also referred to
as DMD.
This disease is characterized by mutations of the DMD gene
on the X chromosome,
which can lead to progressive
weakening of the muscles,
in our bodies,
eventually leading to death. It was originally discovered in the
1860s but it wasn't until 1986 that the gene responsible
for the disease was located on the X chromosome.
Let's take a deep dive into what makes this disease
unique and how we can respond to it.
effectively.
Some of the first things that patients afflicted with the
disease may notice include difficulties with walking, rising.
abnormal clumsiness and other types of weakness in movements of
the shoulder and pelvis regions.
They may also experience difficulty with climbing stairs, walking on
their tiptoes,
some leg pain and facial weakness.
Generally, the age of onset for DMD is around 3
to 5 years old.
As the condition progresses,
it can start to affect muscles responsible for breathing
and the cardiac muscle tissue, resulting in breathing difficulties and
irregular heartbeat.
One of the ways in which DMD can be diagnosed
is by looking at a person's family history,
given that it can be genetically inherited. Genetic testing may
also identify the disease.
However,
it can be fairly expensive.
Other diagnostic methods include blood testing for elevated
creatine kinase levels.
High levels of this enzyme are thought to be predictive
of the onset of DMD as this enzyme is present
in muscles that break down.
Some other characteristics that might be useful for a
diagnosis
can include scoliosis,
a curving of the spine,
pseudohypertrophy, muscular
enlargement through the
accumulation of fat, as well as reduced reflexes, problems with
balance and coordination when walking and other issues related to
the heart muscle.
While there is currently,
no cure for DMD,
there are numerous therapeutic options that can help delay
symptoms of the disease.
These can include physiotherapy to prevent muscle weakness, respiratory therapy to maintain
breathing ability and speech therapy to prevent breakdown to
the muscles of the face.
Surgery can also be an option to prevent the onset
of more serious symptoms, such as through the implementation of
a pacemaker to address problems with the heart's rhythm,
or through the correction of scoliosis to maintain breathing. Medication,
such as steroids can be prescribed to reduce the speed
of muscle weakening and improve muscle strength, immunosuppressants to delay
damage to the muscle cells, seizure medications to address muscle spasms, and beta blockers to slow
the heart rate and delay.
the onset of associated heart muscle problems.
Gene therapy is another option,
however,
it is not widely accessible for treatment. Moving on, we are going to cover Becker muscular dystrophy, which is also a progressive
muscular degenerative disease.
Becker muscular dystrophy was named after Peter Emil Becker,
a German physician who discovered the variant in the 1950s.
Patients with this variant face various symptoms by their teen
or young adult years, such as difficulty walking, pain in
their muscles or muscle spasms, walking on their toes, tiredness
being intolerant to exercise or frequently falling. This form of
muscular dystrophy is diagnosed using blood tests that look at creatine
kinase levels.
Creatine kinase is a form of protein.
mainly found in muscle cells are damaged, as mentioned previously
in DMD.
Similarly,
using blood tests,
doctors can determine if the dystrophin gene is
present.
Electrocardiograms, also known as EKGs, use a device that records
the electrical signals produced by the heart.
In this case,
it can be used to detect heart damage caused by
the dystrophin gene.
Furthermore, a muscle biopsy may be performed by taking a
tissue sample using a biopsy needle. Using this method,
doctors can determine if the muscle contains dystrophin.
Decreased levels of dystrophin found around the
muscle fibers are an indicator of Becker muscular
dystrophy.
Finally,
there are various treatment methods as Becker muscular dystrophy
cannot be prevented or cured.
These methods include using corticosteroids and anti-inflammatory medication,
ACE inhibitors and beta-blockers for cardiomyopathy, a disease which affects
heart muscle, as these medications,
lower blood pressure and heart rate
respectively. Alongside medication, rehabilitation can help patients' mobility and overall
quality of life. Patients can also opt to get surgery
for scoliosis and contractures
which is the tightening of the muscles or tendons. Duchenne
muscular dystrophy versus
Becker muscular dystrophy:
The similarities and differences. The symptoms of both Duchenne and
Becker muscular dystrophy are extremely similar.
However, differences
do exist. The age of onset for Duchenne muscular dystrophy
is between 3 to 5 whereas for muscular dystrophy it ranges from 11
to early 20s and is highly variable, meaning that it can
even take place later on in life. In terms of
the diagnosis, for Duchenne, a clinical evaluation is performed alongside
a thorough analysis of patient history,
molecular genetics,
testing as well surgical interventions in some cases, whereas for Becker,
physical symptoms and family
history are assessed.
Blood testing is performed as a diagnostic procedure for both
conditions as previously,
discussed. Duchenne muscular dystrophy is known to progress
rapidly, resulting in a
decreased life expectancy and an increased chance of
health complications, whereas Becker
muscular dystrophy progresses at a slower rate which leads to
an increased life expectancy and milder health complications.
There is no treatment for both forms of muscular dystrophy.
However,
strategies to manage symptoms
do exist. In both cases,
physical therapy is advised to keep the body active and
in motion, surgery to treat contractures and scoliosis as well
as medication, specifically corticosteroids to maintain muscle strength and limit
disease progression.
The life expectancy for Duchenne muscular dystrophy is between 20
to 30 due to its early onset and rapid progression,
whereas the life expectancy for Becker muscular dystrophy is
40 to 50
due to its slow progression and late onset.
The genetic mechanism responsible for both Duchenne and
Becker
muscular dystrophy is identical.
as these conditions are characterized by having an X-linked recessive
inheritance pattern. This indicates that the mutated gene is located
on the X chromosome of the affected individual. Since females have
two X chromosomes and males have one X chromosome,
these conditions are most likely to affect males.
The Punnett Square demonstrates the offspring of an unaffected carrier mother
and an unaffected father, resulting
In a 25% chance that their child will inherit Duchenne or Becker
muscular dystrophy, with a 25% chance of the child being a
carrier of the disease.
These outcomes can vary depending on the genotype of the mother and father. Overall, to inherit these conditions, the defective
gene must be inherited either from the mother or the father
or both for the child to express Duchenne or Becker
muscular dystrophy,
The cellular mechanism responsible for Duchenne and Becker muscular dystrophy is caused by the inheritance of the defective dystrophin
gene on the X chromosome.
The DMD Gene is,
the largest human gene, which makes it highly prone to mutations,
and functions to synthesize the dystrophin
protein.
Mutations in the DMD gene are caused by deletions and duplications
which, as a result, disrupt dystrophin production. Insufficient dystrophin production
is extremely detrimental to the body as it leads to
the instability of muscular structures, specifically compromising the strength and
integrity of muscle
fibres across the body.
This interferes with the ability of the muscles to contract
and relax effectively and increases the chances of injury. The
mutation in the DMD gene in causing Duchenne muscular dystrophy
leads to the complete absence of the dystrophin protein,
which explains the rapid disease progression
and low life expectancy.
Whereas the mutation in the DMD gene causing Becker muscular
dystrophy
leads to very little production of dystrophin,
which explains the slower progression
and the higher life expectancy. Duchenne and Becker muscular dystrophy are extremely rare
muscular diseases. Duchenne muscular dystrophy impacts
one
in three thousand
five hundred males, with 2.8
cases per 100,000
individuals, whereas Becker muscular dystrophy impacts 1 in 18,518 males with
1.6
cases per 100,000
individuals. Distinguishing between both of these conditions
allows for growth in terms of disease
prevention and treatment strategies
which could possibly lead to a cure.
Being able to decipher between the two not only spreads awareness
that could lead to a quicker diagnosis and treatment plan,
but this can also better accommodate the individual to receiving services
that will improve their quality of life.
Thank you for watching.
We hope that you were able to learn more about
Duchenne and Becker muscular dystrophy and that you are now able to
distinguish between the two from the knowledge that you have
gained.