CHRNB1 and congenital myasthenic syndrome: Genes associated with channelopathies (SCN4A, CACNA1S, KCNJ2, CLCN1) or congenital myasthenic syndrome and related disorders (CHRNA1, CHRNB1, CHRND, CHRNE, RAPSN, CHAT, MUSK, COLQ, DOK7, AGRN, GFPT1, DPAGT1, LAMB2, CHRNG, PLEC) were specifically checked.