MYMK and congenital fibrosis of the extraocular muscles: Most cases appear sporadic, and although heritability has occasionally been reported,2,3 those investigations included individuals with distinct “Moebius-like” phenotypes, such as hereditary congenital facial paresis,4,5 Duane retraction syndrome,6 congenital fibrosis of the extraocular muscles (CFEOM),7 facioscapulohumeral muscular dystrophy,8 and congenital myopathies associated with facial weakness and ophthalmoplegia, such as Carey-Fineman-Ziter syndrome (MYMK [HGNC:33778], OMIM 254940)9 or STAC3 (HGNC:28423, OMIM 255995)- and RYR1 (HGNC:10483, OMIM 255320)-related myopathies.10