Next Generation Molecular Diagnosis of Hereditary Spastic Paraplegias: An Italian Cross-Sectional Study.

D'Amore A1,2, Tessa A1, Casali C3, Dotti MT4, Filla A5, Silvestri G6,7, Antenora A5, Astrea G1, Barghigiani M1, Battini R1, Battisti C4, Bruno I8, Cereda C9, Dato C10, Di Iorio G10, Donadio V11, Felicori M12, Fini N13, Fiorillo C14, Gallone S15, Gemignani F2, Gigli GL16, Graziano C17, Guerrini R18, Gurrieri F19, Kariminejad A20, Lieto M5, Marques LourenḈo C21, Malandrini A4, Mandich P22,23, Marcotulli C3, Mari F18, Massacesi L24, Melone MAB10, Mignarri A4, Milone R25, Musumeci O26, Pegoraro E27, Perna A6,7, Petrucci A28, Pini A12, Pochiero F29, Pons MR30, Ricca I1, Rossi S6,7, Seri M17, Stanzial F31, Tinelli F1, Toscano A26, Valente M16, Federico A4, Rubegni A1, Santorelli FM1.

Author information

Abstract

Hereditary spastic paraplegia (HSP) refers to a group of genetically heterogeneous neurodegenerative motor neuron disorders characterized by progressive age-dependent loss of corticospinal motor tract function, lower limb spasticity, and weakness. Recent clinical use of next generation sequencing (NGS) methodologies suggests that they facilitate the diagnostic approach to HSP, but the power of NGS as a first-tier diagnostic procedure is unclear. The larger-than-expected genetic heterogeneity-there are over 80 potential disease-associated genes-and frequent overlap with other clinical conditions affecting the motor system make a molecular diagnosis in HSP cumbersome and time consuming. In a single-center, cross-sectional study, spanning 4 years, 239 subjects with a clinical diagnosis of HSP underwent molecular screening of a large set of genes, using two different customized NGS panels. The latest version of our targeted sequencing panel (SpastiSure3.0) comprises 118 genes known to be associated with HSP. Using an in-house validated bioinformatics pipeline and several in silico tools to predict mutation pathogenicity, we obtained a positive diagnostic yield of 29% (70/239), whereas variants of unknown significance (VUS) were found in 86 patients (36%), and 83 cases remained unsolved. This study is among the largest screenings of consecutive HSP index cases enrolled in real-life clinical-diagnostic settings. Its results corroborate NGS as a modern, first-step procedure for molecular diagnosis of HSP. It also disclosed a significant number of new mutations in ultra-rare genes, expanding the clinical spectrum, and genetic landscape of HSP, at least in Italy.