CANVAS: A New Genetic Entity in the Otorhinolaryngologist's Differential Diagnosis

Abstract

Objective: The biallelic inheritance of an expanded intronic pentamer (AAGGG)_exp in the gene encoding replication factor C subunit 1 (RFC1) has been found to be a cause of cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS). This study describes clinical and genetic features of our patients with clinical suspicion of the syndrome.

Study design: A retrospective descriptive study from an ataxia database comprising 500 patients.

Setting: The study was performed at the Otorhinolaryngology Department of a hospital in the north of Spain.

Methods: Specific genetic testing for CANVAS was performed in 13 patients with clinical suspicion of complete or incomplete syndrome. The clinical diagnosis was supported by quantitative vestibular hypofunction, cerebellar atrophy, and abnormal sensory nerve conduction testing.

Results: Nine of 13 (69%) patients met clinical diagnostic criteria for definite CANVAS disease. The first manifestation of the syndrome was lower limb dysesthesia in 8 of 13 patients and gait imbalance in 5 of 13. Eleven of 13 (85%) patients were carriers of the biallelic (AAGGG)_exp in RFC1.

Conclusion: A genetic cause of CANVAS has recently been discovered. We propose genetic screening for biallelic expansions of the AAGGG pentamer of RFC1 in all patients with clinical suspicion of CANVAS, since accurate early diagnosis could improve the quality of life of these patients.

Keywords: CANVAS; DNA repeat expansion; bilateral vestibulopathy.