The Genetic Landscape of Hereditary Spastic Paraplegia in Greece.

Hereditary spastic paraplegia (HSP) is a neurogenetic disorder characterized by progressive, length-dependent degeneration of the upper motor neurons. We investigated 112 Greek HSP index cases collected over more than 25 years from all regions of the country, using a combination of next generation sequencing and multiplex ligation-dependent probe amplification. In total, we identified a causative variant in 68 patients, corresponding to a diagnostic yield of 60.7%. The diagnostic yield was 62.8% in autosomal dominant HSP, 77.8% in autosomal recessive HSP and 50.0% in sporadic cases. We identified 7 novel causative variants in SPAST, SPG7, and CYP7B1. We found causative variants in a total of 18 different genes. The most commonly involved genes, affecting more than one family, were SPAST (25.0%), SPG11 (12.5%), CYP7B1 (3.6%), SPG7 (3.6%), KIF5A (2.7%), ABCD1 (1.8%) and PSEN1 (1.8%). Variants in ATL1, REEP1, BSCL2, PLP1, WASCHC5, AP5Z1, CYP27A1, SOD1, POLR3A, GFAP and ARG1 were identified in single families. This study presents a comprehensive overview of the phenotypic and genotypic spectrum of HSP in the Greek population, expanding previous data, and contributing to the characterisation of further pathogenic variants linked to HSP.