Increasing involvement of CAPN1 variants in spastic ataxias and phenotype-genotype correlations
Jean‐Loup Méreaux, Cristina Firanescu, Giulia Coarelli, Malin Kvarnung, Rita Rodrigues, Elena Pegoraro, Meriem Tazir, Frédéric Taithe, Rémi Valter, Vincent Huin, Kristina Lidström, Guillaume Banneau, Sara Morais, Livia Parodi, Marie Coutelier, Mélanie Papin, Per Svenningsson, Jean‐Philippe Azulay, Isabel Alonso, Daniel Nilsson, Alexis Brice, E. Le Guern, Rayomand Press, Giovanni Vazza, José Leal Loureiro, Cyril Goizet, Alexandra Dürr, Martin Paucar, Giovanni Stévanin
Abstract
Spastic ataxias are rare neurogenetic disorders involving spinocerebellar and pyramidal tracts. Many genes are involved. Among them, CAPN1, when mutated, is responsible for a complex inherited form of spastic paraplegia (SPG76). We report the largest published series of 21 novel patients with nine new CAPN1 disease-causing variants and their clinical characteristics from two European university hospitals (Paris and Stockholm). After a formal clinical examination, causative variants were identified by next-generation sequencing and confirmed by Sanger sequencing. CAPN1 variants are a rare cause (~ 1.4%) of young-adult-onset spastic ataxia; however, together with all published cases, they allowed us to better describe the clinical and genetic spectra of this form. Truncating variants are the most frequent, and missense variants lead to earlier age at onset in favor of an additional deleterious effect. Cerebellar ataxia with cerebellar atrophy, dysarthria and lower limb weakness are often associated with spasticity. We also suggest that cognitive impairment and depression should be assessed specifically in the follow-up of SPG76 cases.