KIF21A and congenital fibrosis of the extraocular muscles: As detailed below, this includes rare KIF21A missense variants reported to cause not only CFEOM, but also facial weakness with or without progressive axonal motor-sensory polyneuropathy and intellectual/social disabilities (Ali et al., 2013; Soliani et al., 2020; Jia et al., 2022) increasing the overlap between KIF21A-CFEOM and TUBB3-CFEOM phenotypes.