Mutations were excluded in most CMS genes (including CHRNB1, CHRNE, CHRND, DOK7, RAPSN, DPAGT1, and GFPT1) but a single heterozygous de novo variant predicted to be pathogenic was identified in CHRNA1 (c.812T > G, p.Leu271Arg) (transcript numbering according to ENST00000348749.9, which does not harbor the P3A exon, but contains the 20 amino acid signal sequence; thus the mutation is at position Leu251Arg excluding the signal sequence). Here, RAPSN is linked to congenital myasthenic syndrome.