Initially, two loci for inherited CMs were identified on chromosome 5 (5q14-21 and 5q13-22), and later, the RASA1 (RAS P21 Protein Activator 1) gene was identified as a candidate gene for atypical CMs with AVMs and AVFs, and sporadically, in PWS [16,18]. Here, RASA1 is linked to congenital myasthenic syndrome.