The role of extracellular calcium in the pathophysiology of myotonic dystrophy.

Increased intracellular calcium levels in myotonic dystrophy have been repeatedly reported in many studies. In our recent investigations, the entrance of extracellular calcium ions through voltage sensitive calcium channels (VSCCS) during repetitive action potentials and late after potentials (LAPs) in tetanic responses were found. Since there is an increased amplitude of LAPs and after-discharges in muscle fibers of myotonic dystrophy, we suggest that this pathological increase in the electrical properties of the muscle could also be responsible for this elevated intracellular calcium level.