The genetic architecture of primary lateral sclerosis in a cohort of Italian patients

Background and purpose: Recent studies suggest that primary lateral sclerosis (PLS) may have a genetic component. In this work, we performed a next-generation sequencing (NGS) analysis in order to explore the genetic architecture of PLS in a cohort of Italian patients. Methods: NGS was conducted to analyze 228 genes associated with amyotrophic lateral sclerosis (ALS), hereditary spastic paraplegia (HSP), and parkinsonian syndromes (PS) in a cohort of PLS patients diagnosed between 2003 and 2021 at our center. All patients were also screened for C9orf72 hexanucleotide repeat expansion (C9orf72-HRE) by repeat-primed PCR. Genetic variants were classified according to the ACMG criteria. Results: In our study, including 47 PLS patients, we detected 22 rare variants in 17 patients, including 8 likely pathogenic or pathogenic variants and 14 variants of uncertain significance. Four patients carried more than one variant. Among the variants identified, 18 (81.8%) were found in ALS-associated genes. Variants in TBK1 were associated with extra-motor involvement. Conclusions: Although the majority of the PLS patients in our cohort tested negative for an expanded panel of genes associated with ALS, HSP and PS, in 36.2% of the cases, a genetic variant was identified and it mostly belongs to genes associated with ALS, including a C9orf72 expansion and a rare SOD1 variant. Based on these results, we emphasize the need for genetic screening in PLS patients. Further studies on the genetic background are necessary to better understand the complex pathomechanism of each phenotype within the MND-FTD spectrum disorder.