Myotonia associated with caveolin-3 mutation.

Introduction: Caveolin-3 is a major component of the caveolae in skeletal and cardiac muscle. Mutations in the caveolin-3 gene (CAV3) lead to a spectrum of clinical phenotypes including limb-girdle muscular dystrophy 1C, distal myopathy, rippling muscle disease, isolated hyperCKemia, and cardiomyopathy.

Case Report: A 24-year-old man with myalgia, muscle stiffness, and fatigue has normal strength and prominent myotonic discharges in the gastrocnemius. He also has epilepsy. He harbors a heterozygous CAV3 mutation, p.V57M. He has no mutations in CLCN1 and SCN4A, and he had normal genetic testing for myotonic dystrophy type 1 and type 2.

Conclusions: Mutations in CAV3, and in particular p.V57M in CAV3, previously reported in isolated familial hyperCKemia, can be associated with electrical myotonia.