Mutations in MUSK are a known cause of congenital myasthenic syndrome (CMS), but a limited number of cases have been reported to date despite the increasing use of next‐generation sequencing (Ammar et al., 2013; Chevessier et al., 2004; Giarrana et al., 2015; Luan, Tian, & Cao, 2016; Maselli et al., 2010; Mihaylova et al., 2009; Murali, Li, Grand, Hakonarson, & Bhoj, 2019; Owen et al., 2018). Here, MUSK is linked to congenital myasthenic syndrome.