• Autosomal-dominantly inherited nondystrophic myotonic disorders are an interesting group
of muscle diseases that provide considerable opportunity for future molecular genetic
studies to identify the genes responsible for specific membrane functions. A family with such
a myotonic disorder is described with features that are distinctly different from myotonia
congenita and paramyotonia congenita. Five members were affected in three generations.
The myotonia fluctuated to an unusual degree. It did not worsen with cold but increased …