The figures I have seen are about 1:100,000 world-wide, except for Sweden, where it appears to be much more prevalent, at approximately 1:10,000. This is for Myotonia Congenita, not for all myotonic disorders. I believe these figures are more statistical genetics than actual survey/study numbers, because it is known that there have been many people with these gene mutations who were not diagnosed until fairly recently (if ever!). It will be interesting to see how (or if) the stats change as DNA testing and understanding of the various mutations enhances information about us.

Type of Myotonia: Myotonia Congenita, Becker's type

Country: USA