Welcome to Mayo Connect. Every day I learn of a new disorder here - I have no personal experience with it, but here you can read an earlier discussion about Myotonic Congenita if you click this link: https://connect.mayoclinic.org/discussion/myotonia-congenita/
Here is some information from the Cleveland Clinic about the disorder: https://my.clevelandclinic.org/health/diseases/22347-myotonia-congenita
And the Muscular Dystrophy Association: https://www.mda.org/quest/article/new-research-channels-for-myotonia-congenita
You may be able to find a support group here:
https://www.aanem.org/Patients/Muscle-and-Nerve-Disorders/Myotonia-Congenita
If you go to the Connect link & share a little about your son's diagnosis, you will probably get a reply.
Sue

Hi @sanders0784 I second Sue's welcome and wanted to let you know that I moved your post to the link that she provided so that you can meet other people who have been diagnosed just like your son. Reference info: Everything You Should Know About Myotonia Congenita: https://www.healthline.com/health/myotonia-congenita
"For some people, myotonia congenita causes mild symptoms that can be managed through lifestyle modifications. But others experience significant ..." -- A Muscle Disease Concealed by a Muscular Physique: https://www.mda.org/quest/article/muscle-disease-concealed-muscular-physique

How old is your son?