Progressive degenerative myopathy, what is this disorder?

Muscle degeneration: There are several types of progressive muscle degeneration. Duchenne muscular dystrophy is one of the better known. Other variants of muscular dystrophy are less severe. Spinal muscular atrophy results from loss of anterior horn cells in the spinal cord that causes progressive degeneration of the involved muscles with weakness. Toxic myopathy can occur including associated with steroid use.