Genotype variability in early-onset Hereditary Spastic Paraplegia: a single-center study

Hereditary spastic paraplegias (HSPs) are genetically and clinically heterogeneous, slowly progressive neurological disorders characterized by primary involvement of the corticospinal tracts. The early-onset forms of HSP (EO-HSP) are often defined as "cerebral palsy mimics" since symptoms begin in infancy and manifest as spastic di- or tetraplegia and possible neurodevelopmental disorder. The rarity and heterogeneity of these disorders make their diagnosis challenging. In this single-center study, we focus on the outcomes and diagnostic detection rate of EO-HSP patients from a cohort of 104 consecutive HSP cases. The discussion highlights the genetic variability in cases of EO-HSP that tested positive through a series of molecular analyses, particularly those requiring further investigation via whole exome sequencing (WES). This approach has shed light on the etiopathogenetic role of 19 variants across 10 different genes (COQ4, FOXG1, GRIN2B, HPDL, LRP2, RBMX, SPART, TBCD, ZBTB11, and ZC4H2) in 14 patients with complex EO-HSP. Notably, most of these genes are not conventionally classified as HSP-related or included in the SPG classification on the Online Mendelian Inherited in Men (OMIM) catalog. We emphasize the importance of detailed genotype-phenotype correlations and the diagnostic potential of a highly specialized translational approach in clinically selected cases lacking molecular confirmation, thereby expanding our understanding of the genetic variability of EO-HSP.