Disseration by Sofia Petrova, “Analyse des MUSK- und des COLQ-Gens bei Patienten mit kongenitalem myasthenen Syndrom” 2007 for Medizinischen FakultÃ¤t derLudwig-Maximilians-UniversitÃ¤t zu MÃ¼nchen. Using Google Translate, it looks like this dissertation lists T100M as a nonpathogenic polymorphism seen in one patient & father.
CMS is quite rare, GeneReviews seems to support ~ 1 / 100,000 as a high end estimate. An as-yet-undiscovered pathogenic responsible for 10% of disease might be expected to have an allele frequency of .03% (.1 * (1 / 100,000)**0.5). The chances of seeing such a rare variant in twice in 124 random alleles is quite low (p=0.0007).