TUBB3 and congenital fibrosis of the extraocular muscles: While variants in KIF21A usually cause isolated CFEOM (CFEOM1; MIM: 135700) [15,21], those in TUBB3 are associated with either isolated or syndromic CFEOM (CEOM3A MIM: 600638), in which additional features (e.g., DD/ID, learning disabilities, and brain structural defects) occur, and complex cortical dysplasia with other brain malformations (CDCBM1; MIM: 614039) [16,22].