is a compensation for loss of muscle strength. However, the enlarged muscle
tissue is eventually replaced by fat and connective tissue (pseudohypertro-
phy). Muscle contractures occur in the legs, rendering the muscles unusable
as muscle fibers shorten and fibrosis occurs in connective tissue. Intellectual
impairment may also occur although it is not inevitable and does not worsen
as the disorder progresses. At school age, there is trouble climbing stairs and
the child may walk on his toes or the balls of his feet and can easily fall over.
Characteristically, the belly is stuck out and shoulders held back to maintain
balance. Nearly all children with DMD lose the ability to walk between seven
and 12 years and, by 10, braces may be required for walking. Bones develop
abnormally leading to skeletal deformities of the spine and other areas. In the
early teens, or earlier, the heart and respiratory muscles may also be affected.
Cardiomyopathy is commonly present, but signs of congestive heart failure
or arrhythmias (Chapter 14) are rare. The muscular weakness and skeletal
deformities frequently lead to breathing disorders, including pneumonia. The
aspiration of food or fluid into the lungs is common during the later stages.
Death usually occurs by age 25, typically from these respiratory disorders.
The symptoms of BMD are considerably milder than those of DMD. They
usually begin about the age of 12 or in early adulthood. The pattern of
development resembles that of DMD although the course is slower and far
less predictable. Generally, muscle wasting begins in the legs and pelvis
and then progresses to the muscles of the shoulders and neck, followed
by loss of arm muscles and respiratory muscles. Calf muscle enlargement
(pseudohypertrophy) is again apparent. The rate of muscle tissue degeneration
in BMD varies greatly. Some men require wheelchairs by their thirties, others
manage for many years with minor aids, such as walking sticks, and, indeed,
the ability to walk may continue to the age of 40 or over. Cardiomyopathy
is less common than with DMD. If it does occur, then, like DMD, congestive
heart failure or arrhythmias are rare. Death usually occurs in the fifth decade
but some patients live to an advanced age.
Diagnosis and treatment of muscular dystrophies
A diagnosis of MDs begins with a family history and physical examination.
The pattern of weakness can be particularly helpful and usually the source
of weakness, whether in motor neurons or muscle tissue, can be identified
by a physical examination. Nerve conduction studies can indicate whether
the underlying problem is in the muscles or the nerves. However, an
electromyography (EMG) measures the electrical activity of the muscles and
can show if the weakness is caused by destruction of muscle tissue. Another
early diagnostic test would be to measure creatine kinase (CK) activity of the
blood to assess any leakage of the enzyme from damaged muscle. An increase in
CK levels is seen in MDs but also in other conditions, such as an inflammation.
A magnetic resonance (MR) scan can be useful in visualizing intramuscular
activity. Genetic testing and a muscle biopsy can confirm a diagnosis and both
are essential since other diseases, such as limb-girdle MD and spinal muscular
atrophy, present with some of the same symptoms. Biopsy material can also
distinguish MDs from inflammatory and other disorders as well as identify the
type of dystrophy present. Diagnostic tests using DNA of blood or muscle cells
can give precise clinical information, and their use is expanding. A diagnosis
of BMD is often not made until adolescence or even adulthood, when physical
activities become difficult.
There are no known cures for DMD or BMD. In both diseases, the goal of
treatment is to control the symptoms to promote the quality of life. Inactivity,
such as prolonged bed rest, generally worsens muscle disease and so physical
activity is encouraged. Physiotherapy may be helpful in maintaining muscle
strength and coordination. Orthopedic appliances, for example leg braces,
walking sticks and wheelchairs, may improve mobility and the ability for self-
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