|Myopathies can cause weakness or stiffness in all of the body's voluntary muscles. Because muscles support the body's posture, muscle weakness can lead to skeletal deformities.|
The word myopathy means “disease of muscle.” More specifically, myopathies are diseases that cause problems with the tone and contraction of skeletal muscles (muscles that control voluntary movements.)
Inherited myopathies have a genetic basis, meaning they can be passed from parent to child.
Endocrine myopathies are not inherited and result from abnormal activity of the thyroid gland.
Congenital (present at birth) inheritable myopathies can cause severe, general muscle weakness that complicates basic activities like swallowing and breathing. Other inheritable myopathies cause episodes of muscle weakness or stiffness (myotonia) that are milder and more temporary in nature.
Symptoms of endocrine myopathies include weakness and atrophy (shrinking) of the muscles around the shoulders and hips, muscle stiffness, cramps, slowed reflexes, and in severe cases, muscle breakdown.
In the inherited myopathies, genetic mutations cause defects in various proteins necessary for muscle tone and contraction. In endocrine myopathies, symptoms result from too much or too little hormone production from the thyroid gland. See Causes/Inheritance.
Myopathies usually don’t cause muscles to die but keep them from working properly. Myopathies are usually nonprogressive — that is, a myopathy usually doesn’t grow worse over a person’s lifetime. In fact, some children with myopathies gain strength as they grow older.
MDA-supported scientists have made great strides in the last decade in identifying the genetic mutations that are at the root of several inherited myopathies. Researchers are building on this knowledge to develop treatments and therapies for these diseases. See Research.