Hi,
There are currently 102 known defects in the SCN4a gene. About thirty (30) of them present phenotypically distinct disorders. Several of the 72 remaining were created in research labs to present very narrowly defined disorders for ease of testing. Because the bulk of
SCN4a defects are very rare and present with mixed symptoms, or with some mild symptoms
they may be cataloged as benign. Some symptoms consistent with Thomsens may be the result
the Sodium Channel defect instead.

Athena Diagnostics has a computer model that says that my SCN4a defect is benign but my delayed onset, Potassium Aggravated Myotonia has shaped my whole life and left me disabled for the last 12 years.

In response to your previous posts I suggested Dr. Stephen Cannon, he is still your best bet for good and complete treatment.

Type of Myotonia: SCN4a

Country: US

Joe,

I agree that the associations are sometimes incorrect. While we have a confirmed CLCN1 mutation that has caused symptoms of Thomsen's Disease all through my family, I recently had a test which indicated I also have a mutation (S524G) on the SCN4A gene. It is also listed as unknown significance, but I am very sensitive to potassium and one of my daughters has symptoms that are consistent with PAM or paramyotonia congenita. She is in a wheelchair much of the time but my other family members with Thomsen's don't seem to be affected by potassium at all and they don't experience the weakness that bothers us.

Is Dr. Cannon in California now?

Jan

Type of Myotonia: Thomsen's

Country: USA

Dr Cannon is Associate Dean of Medicine at the University of Texas Southwestern in Dallas.

Type of Myotonia: SCN4a

Country: US

Thanks, Joe. I emailed him and he responded right away. He said that the amino acid change is in a region of the gene that could impact the channel function. It hasn't been associated yet as disease-causing in research studies, but it would certainly explain our greater sensitivity to potassium and cold as well as weakness that isn't typically seen as much in MC.

Jan

Type of Myotonia: Thomsen's

Country: USA