Central cores resemble target fibers of neurogenic disease, though targets are shorter and temporary. These diseases are due to enzymatic defects in muscle. The major energy sources for muscle are glycogen, glucose and free fatty acids. Defective energy metabolism may cause exercise intolerance. If severe, this may lead to massive cell death.
Morphological changes are often present due to the accumulation of substrate molecules.
In later stages, blood-borne glucose and fatty acids are utilized. This is an autosomal recessive disorder that causes cramps on exercise, as well as myoglobinuria. Glycogen storage can be visualized. Fetal myophosphorylase isoenzyme may be a false positive histochemical reaction in regenerating fibers. This is an autosomal recessive disorder that causes cramps on exercise, as well as myoglobinuria.