The muscular dystrophies (MD) are a
group of genetic diseases
characterized by progressive
weakness and degeneration of the
skeletal muscles that control
movement. There are many forms of
muscular dystrophy, some noticeable
at birth (congenital muscular
dystrophy), others in adolescence
(Becker MD), but the 3 most common
types are Duchenne,
facioscapulohumeral, and myotonic.
These three types differ in terms of
pattern of inheritance, age of
onset, rate of progression, and
distribution of weakness.
Duchenne MD primarily affects
boys and is the result of mutations
in the gene that regulates
dystrophin - a protein involved in
maintaining the integrity of muscle
fiber. Onset is between 3-5 years
and progresses rapidly. Most boys
become unable to walk at 12, and by
20 have to use a respirator to
Facioscapulohumeral MD appears
in adolescence and causes
progressive weakness in facial
muscles and certain muscles in the
arms and legs. It progresses slowly
and can vary in symptoms from mild
Myotonic MD varies in the age of
onset and is characterized by
myotonia (prolonged muscle spasm) in
the fingers and facial muscles; a
floppy-footed, high-stepping gait;
cataracts; cardiac abnormalities;
and endocrine disturbances.
Individuals with myotonic MD have
long faces and drooping eyelids; men
have frontal baldness.
Is there any treatment?
There is no
specific treatment for any of
the forms of MD. Respiratory
therapy, physical therapy to
prevent painful muscle
appliances used for support, and
corrective orthopedic surgery
may be needed to improve the
quality of life in some cases.
Cardiac abnormalities may
require a pacemaker.
Corticosteroids such as
prednisone can slow the rate of
muscle deterioration in patients
with Duchenne MD but causes side
effects. Myotonia is usually
treated with medications such as
mexiletine, phenytoin, or
What is the prognosis?
of MD varies according to the
type of MD and the progression
of the disorder. Some cases may
be mild and progress very slowly
over a normal lifespan, while
other cases may have more marked
progression of muscle weakness,
functional disability, and loss
of the ability to walk. In
Duchenne MD, death usually
occurs in the early 20s.
What research is being done?
supports a broad program of
research on MD. The goals of
these studies are to understand
MD and to develop techniques to
diagnose, treat, prevent, and
ultimately cure muscular