Definition of Muscle, central core disease of

Muscle, central core disease of: One of the conditions that produces 'floppy baby' syndrome. Central core disease of muscle causes hypotonia (low muscle tone) in a newborn baby, slowly progressive muscle weakness, and muscle cramps after exercise. Muscle biopsy shows a key diagnostic finding of absent mitochondria in the center of many muscle fibers. It is caused by an abnormal gene on chromosome 19 involving ryanodine receptor 1, and is inherited as a dominant trait.