I had a DNA and nerve conduction test. My mother had never been tested. Her brother's daughter and grandson has Thomsen Myotonia. Therefore, my mother has to be the carrier. No one on my Dad's side has Myotonia. My mother does not have any symptoms of myotonia.
I do believe that my mother takes medicine for high cholesteral.
Judy, my mutation is G230E and myotonia runs all through my mother's family, but she never had symptoms. Her doctor was very surprised when she showed up with myotonic discharges on the EMG.
This is a link to an earlier post where I listed all the contraindicated medications for cholesterol treatment and high blood pressure:
Hope that helps. She may be a slow metabolizer genetically, or her age may be causing her to metabolize medications more slowly which can cause elevated blood levels and more severe side effects.