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Re: My dad has Thomsens disease and I have a question about inheritance

Hi,

the code for my disorder is c.920T>C (p.Phe307Ser). I am the only one in family who has got it, but the doctor and lab say it is known to be both dominant and recessive so that I can never really know which type I have got. And when I check on internet they also say that it could be both. This is very confusing.
someone out there with the same mutation?

Type of Myotonia: thomsen

Country: germany

Re: My dad has Thomsens disease and I have a question about inheritance

As your doctor said, yours is one of the mutations that can go either way. Here's an article about it (the notation is F307S):

Variable Penetrance of Mutations

My family has one of those types, although not the same mutation. So one of your parents has the mutation, but it didn't cause symptoms. The same was true for me...my mother had no symptoms. Variable penetrance means the mutation can get passed through several generations and cause symptoms in some and not in others. They don't seem to know what makes the difference. It may have to do with other genetic factors that further inhibit the chloride ion channel.

So if you have children, they will have a 50% chance of inheriting the gene, but it would be impossible to know whether it would cause symptom of myotonia congenita. It is important for your family members to have their anesthesiologists use the protocol for myotonia (malignant hyperthermia) and monitor potassium during surgery. Just carrying the gene will be enough to make them susceptible to a reaction. Dr. Lehmann-Horn's lab in Ulm can test for the mutation in other family members, even if they have no symptoms.

Here's his contact information if you don't have it:

Frank Lehmann-Horn M.D. Ph.D.
Hertie Senior Research Professor
Division of Neurophysiology
University of Ulm
Albert-Einstein-Allee 11
89081 Ulm/Germany
Phone: +49 (0)731 / 500 - 23250
Fax: +49 (0)731 / 500 - 23260

Jan

Type of Myotonia: Thomsen's

Country: US