<unk> , a form of Myotonia congenita, is a muscular genetic disorder characterized by muscle stiffness (cramp) and an inability of the muscle to relax after a voluntary contraction. The affected muscle functions normally after a few repetitions.
Thomsen disease
Fox-Fordyce disease
Kummell disease
Salla disease
Pott's disease
Gunther disease
Sneddon-Wilkinson disease
Darier's disease