No other likely candidate gene was identified in the targeted analysis of the exomes; in particular no disease-causing variant in any of the known congenital myasthenic syndrome (CMS) genes (RAPSN, CHRNE, AGRN, ALG2, CHAT, CHRNA1, CHRNB1, CHRND, CHRNE, COLQ, DOK7, GFPT1, GMPPB, MUSK, PREPL and SLC5A7) was found. The gene discussed is GMPPB; the disease is congenital myasthenic syndrome.