KARS1 and inborn mitochondrial metabolism disorder: Pendular nystagmus, ophthalmoplegia, jerky eye movements are typical clinical signs of mitochondrial diseases (Schrier & Falk, 2011) and have been reported in individuals with KARS1 defects (Ardissone et al., 2018; Fuchs et al., 2019; Itoh et al., 2019; Joshi et al., 2016; Kohda et al., 2016; Lieber et al., 2013; McMillan et al., 2015).