The CFEOM3 phenotype can have variable expression with bilateral or unilateral oculomotility defects ranging from complete ophthalmoplegia to mild restrictions, including isolated bilateral upgaze palsy.6 7TUBB3 mutations have also been described in patients with Moebius syndrome.12 The E421D syndrome described here has variable expression which can include bilateral or unilateral ophthalmoplegia, ptosis, pathological synkinesis, mild learning difficulty, facial nerve palsy, focal cortical dysplasia and mild ataxia. Here, TUBB3 is linked to cerebellar ataxia.