Myopathy: Any and all disease of muscle. Or any type of damage to muscle. There are many different kinds of myopathies.

The most common form of muscular dystrophy, for example, is an inherited myopathy; it is due to mutation of a gene on the X chromosome. The mitochondrial myopathies are a group of neuromuscular diseases caused by damage to the mitochondria, energy-producing structures in cells that serve as power plants. Other myopathies are metabolic; they result from disturbances in metabolism. Drugs such as the statins can also be myopathic and damage muscle.

From myo- (muscle) + -pathy (disease or disorder).