Hereditary spastic paraplegia (HSP) represents a genetically heterogeneous group of neurodegenerative disorders characterized by progressive axonal degeneration of corticospinal upper motor neurons, leading to lower limb-predominant spasticity and weakness. To date, 83 HSP subtypes have been reported, exhibiting either pure or complicated phenotypes. Among these, spastic paraplegia type 64 (SPG64) is an ultra-rare form of complicated HSP caused by biallelic variants in ENTPD1, which encodes an ectonucleotidase involved in purine metabolism. In this study, we report a proband presenting with neurodevelopmental regression, dysmorphic features and sensorimotor polyneuropathy, followed comprehensively for 6 years. Genetic analysis identified a novel homozygous NM_001776:c.1174C>T;p.Gln392Ter variant in ENTPD1. A literature review reveals that 39 individuals with SPG64 have been reported, with clinical manifestations including cognitive decline (38/39), speech abnormalities (30/39) and brain malformations (16/31). However, aspects of the full phenotypic spectrum remain to be fully characterized. Notably, this case represents the first documented patient with long-term follow-up, providing valuable clinical insights into disease progression over time. Neuroimaging in the proband demonstrated the involvement of the posterior limb of the internal capsule and the 'ear of the lynx' sign, which was not previously reported in SPG64. Furthermore, the presence of sensorimotor polyneuropathy supports that neuropathy may be a previously unappreciated component of SPG64. Our findings highlight the importance of deep phenotyping and long-term follow-up in fully understanding the nature of this unique HSP subtype.

Biallelic HPDL variants have been identified as the cause of a progressive childhood-onset movement disorder, with a broad clinical spectrum from severe neurodevelopmental disorder to juvenile-onset pure hereditary spastic paraplegia type 83. This study aims at delineating the geno- and phenotypic spectra of patients with HPDL-related disease, quantitatively modeling the natural history, and uncovering genotype-phenotype associations. A cross-sectional analysis of 90 published and 1 novel case was performed, using a Human-Phenotype-Ontology-based approach. Unsupervised phenotypic clustering was used alongside in silico analyses to identify distinct patient subgroups. The study models the natural history of the HPDL-related disease in a global cohort, clarifying the molecular and phenotypic spectrum and identifying 3 distinct subgroups characterized by differences in onset, clinical trajectories, and survival. It establishes genotype-phenotype associations, showing that the presence of moderately pathogenic missense variants in 1 allele leads to a milder, spastic paraplegic phenotype with later disease onset, whereas biallelic, highly pathogenic missense or truncating variants are associated with a more severe phenotype and reduced life span. Quantitative and unbiased natural history modeling in HPDL-related disease reveals significant genotype-phenotype associations, providing a foundation for variant interpretation, anticipatory guidance, and choice of outcome measures in future prospective and functional studies.

Current clinical scales that track disease progression are more tailored to spasticity or ataxia, with limited sensitivity to change. The aim was to develop a sensitive and valid scale specifically geared towards optimized sensitivity to change and adapted to patients presenting with both spasticity and ataxia. Longitudinal data from 127 spastic paraplegia type 7 (SPG7) and 112 autosomal recessive spastic ataxia Charlevoix-Saguenay (ARSACS) patients were collected within the multicenter PROSPAX study. Sensitivity to change over 2 years of 30 items from the Scale for the Rating and Assessment of Ataxias (SARA), Spastic Paraplegia Rating Scale (SPRS), and the Activities of Daily Living subscale of the Friedreich's Ataxia Rating Scale (FARS-ADL) was evaluated. Items that demonstrated the highest sensitivity to change were used to build the Spastic Ataxia Composite scale (SPAXCOM). With seven items, the SPAXCOM showed an effect size of 0.71, higher than reference scales (SARA: 0.43, SPRS: 0.42, FARS-ADL: 0.27). The SPAXCOM had a similar sensitivity to change for both genotypes and was more sensitive in participants with a SARA lower than 10 and within the intermediate disease stage (FARS-Disease Staging: 2-3.5). The SPAXCOM showed a high correlation with disease duration (r = 0.67 [0.60; 0.72]) and disease stage (r = 0.86 [0.83; 0.89]). Perception of improvement, stagnation, and worsening were associated with a mean yearly SPAXCOM change of 0.44 (-0.14; 1.01), 0.61 (0.19; 1.03), and 1.22 (0.96; 1.49), respectively. The SPAXCOM is more sensitive to change and homogeneous across genotypes than the reference scales, allowing a reduction of the required sample size in future clinical trials. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Hereditary spastic paraplegias are rare genetic disorders characterized by corticospinal tract impairment. Spastic paraplegia 83 (SPG83) is associated with biallelic mutations in the HPDL gene, leading to varied severities from neonatal to juvenile onset. The function of HPDL is unclear, though it is speculated to play a role in alternative coenzyme Q10 biosynthesis. Here, we report the generation of hiPS lines from primary skin fibroblasts derived from three SPG83 patients with different HPDL mutations, using episomal reprogramming. The patients' clinical characteristics are carefully listed. The hiPS lines were meticulously characterized, demonstrating typical pluripotent characteristics through immunofluorescence assays for stemness markers (OCT4, TRA1-60, NANOG, and SSEA4) and RT-PCR for endogenous gene expression. Genetic integrity and identity were confirmed via Sanger sequencing and short tandem repeat analysis. These hiPS cells displayed typical pluripotent characteristics and were able to differentiate into neocortical neurons via a dual SMAD inhibition protocol. In addition, HPDL mutant neurons assessed via long-term culturing were able to achieve effective maturation, similarly to their wild-type counterparts. The HPDL hiPS lines we generated will provide a valuable model for studying SPG83, offering insights into its molecular mechanisms and potential for developing targeted therapies.

With complicated conditions and a large number of potentially causative genes, the diagnosis of a patient with complex inherited peripheral neuropathies (IPNs) is challenging. To provide an overview of the genetic and clinical features of 39 families with complex IPNs from central south China and to optimize the molecular diagnosis approach to this group of heterogeneous diseases, a total of 39 index patients from unrelated families were enrolled, and detailed clinical data were collected. TTR Sanger sequencing, hereditary spastic paraplegia (HSP) gene panel, and dynamic mutation detection in spinocerebellar ataxia (SCAs) were performed according to the respective additional clinical features. Whole-exome sequencing (WES) was used in patients with negative or unclear results. Dynamic mutation detection in NOTCH2NLC and RCF1 was applied as a supplement to WES. As a result, an overall molecular diagnosis rate of 89.7% was achieved. All 21 patients with predominant autonomic dysfunction and multiple organ system involvement carried pathogenic variants in TTR, among which nine had c.349G > T (p.A97S) hotspot variants. Five out of 7 patients (71.4%) with muscle involvement harbored biallelic pathogenic variants in GNE. Five out of 6 patients (83.3%) with spasticity reached definite genetic causes in SACS, KIF5A, BSCL2, and KIAA0196, respectively. NOTCH2NLC GGC repeat expansions were identified in all three cases accompanied by chronic coughing and in one patient accompanied by cognitive impairment. The pathogenic variants, p.F284S and p.G111R in GNE, and p.K4326E in SACS, were first reported. In conclusion, transthyretin amyloidosis with polyneuropathy (ATTR-PN), GNE myopathy, and neuronal intranuclear inclusion disease (NIID) were the most common genotypes in this cohort of complex IPNs. NOTCH2NLC dynamic mutation testing should be added to the molecular diagnostic workflow. We expanded the genetic and related clinical spectrum of GNE myopathy and ARSACS by reporting novel variants.