Hi, lou
I am also disabled by way of an SCN4a "benign" snp. I was forced to diagnose myself after Neurologists accused me of lying about my symptoms.
I got the requisition from Athena Diagnostics over the internet and filled it out myself. My GP who openly professed no knowledge of neurology signed it (I am sure just to humor me).

There are ancillary conditions that are associated with some sodium channel gene defects. The severity of the ancillary condition is NOT related to the severity myotonic muscle disease.

There are so few people affected that it is suggested (with a question mark)that sensory neuropathy is connected to some sodium channel defects.
A long standing sensory neuropathy often affects the eyes.

Email Jan and have her give you my email address. I can share many documents that my research has found, and give you some suggestions on testing.
Thanks, Joe

Type of Myotonia: SCN4a

Country: US

Hi, lou
I checked the LOVD (Leiden Open Variation Database).
The SCN4a (xxDNA change)p.Val781Ile defect has been reported once
as producing hypokalemic periodic paralysis.

The database lists a number of DNA changes that produce the same amino acid change.
Thanks, Joe

chromium.liacs.nl/LOVD2/variants.php?select_db=SCN4A&action=view_all&order=Variant%2FDNA%2CASC&hide_col=&show_col=&limit=250

That string deliberately does not produce a link but if you copy it into your address bar with or without "http://" as appropriate it should take you to
the right place.

Type of Myotonia: SCN4a

Country: US