Natural History and Phenotypic Spectrum of <scp>GAA‐<i>FGF14</i></scp> Sporadic Late‐Onset Cerebellar Ataxia (<scp>SCA27B</scp>)
Thomas Wirth, Guillemette Clément, Clarisse Delvallée, Céline Bonnet, Thomas Bogdan, Andra Iosif, Audrey Schalk, Jean‐Baptiste Chanson, David Pellerin, Bernard Brais, Virginie Roth, Marion Wandzel, Marie‐Céline Fleury, Amélie Piton, Nadège Calmels, Izzie Jacques Namer, Stéphane Kremer, Christine Tranchant, M. Renaud, Mathieu Anheim
Abstract
BACKGROUND: Heterozygous GAA expansions in the FGF14 gene have been related to autosomal dominant cerebellar ataxia (SCA27B-MIM:620174). Whether they represent a common cause of sporadic late-onset cerebellar ataxia (SLOCA) remains to be established. OBJECTIVES: To estimate the prevalence, characterize the phenotypic spectrum, identify discriminative features, and model longitudinal progression of SCA27B in a prospective cohort of SLOCA patients. METHODS: FGF14 expansions screening combined with longitudinal deep-phenotyping in a prospective cohort of 118 SLOCA patients (onset >40 years of age, no family history of cerebellar ataxia) without a definite diagnosis. RESULTS: Prevalence of SCA27B was 12.7% (15/118). Higher age of onset, higher Spinocerebellar Degeneration Functional Score, presence of vertigo, diplopia, nystagmus, orthostatic hypotension absence, and sensorimotor neuropathy were significantly associated with SCA27B. Ataxia progression was ≈0.4 points per year on the Scale for Assessment and Rating of Ataxia. CONCLUSIONS: FGF14 expansion is a major cause of SLOCA. Our natural history data will inform future FGF14 clinical trials. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.