Congenital fibrosis of the extraocular muscles in a Czech family and its molecular genetic cause

Aim: Congenital fibrosis of the extraocular muscles (CFEOM) is a rare autosomal dominant disorder characterized by bilateral non-progressive ophthalmoplegia and ptosis. The aim of this study was to identify the molecular genetic cause in a four-generation family with CFEOM and to describe the clinical findings in four affected and one unaffected member. Patients and methods: All patients underwent an eye examination. Exons 2, 8, 20 and 21 of the KIF21A gene were directly examined by Sanger sequencing in the proband. Sanger sequencing was also used to test for the presence of the detected mutation in other relatives. Results: Clinical findings were typical in all affected individuals manifesting as ptosis and severely limited vertical and horizontal eye movements with compensatory backward tilt of the head. All patients also had decreased visual acuity attributed to amblyopia and synkinetic eye movements; synergistic convergence on attempted vertical gaze and divergence in the downgaze. A known heterozygous mutation c.2860C>T; p.(Arg954Trp) in KIF21A was identified in all available affected family members with CFEOM. This mutation was not found in a grandson of the proband who had no clinical disease symptoms. Conclusion: CFEOM is a serious disorder leading to life-long functional and often psychological problems.The molecular genetic cause in patients of Czech origin has been discovered for the first time.