Congenital Myopathies
What
is it?
Congenital myopathies are diseases of the skeletal
muscle that are inherited and present at birth.
They cause voluntary muscles to become weak.
Who
gets it?
Children who have at least one parent with a
congenital myophathy have a fifty percent chance
of being born with the disorder. Male and female
children are equally at risk.
Some
forms of congenital myopothies must be inherited
from both parents, each of whom carry a recessive
defective gene but who don't have symptoms of the
disease. Each child of such parents has a
twenty-five percent chance of inheriting both
genes and showing signs of the disease, and a
fifty percent chance of inheriting one defective
gene from only one parent. If the child inherited
just one defective gene, he or she would be a
carrier but would not show signs of the disease.
A few
forms of congenital myopathies develop primarily
in males. Females who inherit the defective gene
are usually carriers without symptoms, like their
mothers, but they can pass on the disease to their
sons. Congenital myopathies are rare and usually
not fatal.
What
causes it?
Congenital myopathies occur when a genetic defect
is linked to a lack of, or a problem with, one of
the proteins needed for normal muscle cell
function. There are several different kinds of
congenital myopathies caused by defective genes,
including central core disease, centronuclear (myotubular)
myopathy, myotonia congenital, nemaline myopathy,
paramyotonia congenita, periodic paralysis (hypokalemic
and hyperkalemic forms) and mitochondrial
myopathies.
What
are the symptoms?
Symptoms of congenital myopathies include mild
weakness of voluntary muscles, especially in the
hips and legs; hip displacement; delays in
reaching developmental milestones; and problems
with running, jumping and climbing stairs.
Some
congenital myopothies can also cause the muscle
weakness in face along with drooping upper
eyelids; long, narrow face; high-arched palate;
jaw projecting beyond upper part of face; muscle
stiffness; decreased or absent reflexes and
periodic paralysis.
How is
it diagnosed?
A
doctor may diagnose a congenital mypothy after
running several tests including one to measure
potassium levels in the blood, a muscle biopsy and
an electromyogram (EMG). An EMG is a test that
records the electrical activity of muscles. During
the test, small electrodes are placed on or in the
patient’s skin so the patterns of electrical
activity can be projected onto a screen or over a
loudspeaker.
What
is the treatment?
Treatment depends on the specific type of
congenital myopathy the patient has. For many
types of congenital myopathies there is no
treatment. A doctor may prescribe medications to
treat various symptoms of congenital myopothies,
but the drugs will not affect the underlying
disease, and attacks of muscle weakness and other
symptoms may still occur.
Self-care tips
For
patients diagnosed with a congenital mypothies,
the treatment and prognosis will vary depending on
the type and severity of the disease. However, one
type of congenital myopothy, muscular dystrophy
(MD), is a much more serious condition. Duchenne's
MD is usually fatal by the late teens, while
Becker's MD is less serious and may not be fatal
until the patient reaches his or her fifties.
This information has been designed as a comprehensive and quick reference
guide written by our health care reviewers. The health information written
by our authors is intended to be a supplement to the care provided by your
physician. It is not intended nor implied to be a substitute for
professional medical advice.
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