BACKGROUND: SINO syndrome (Spastic paraplegia, Intellectual disability, Nystagmus and Obesity) is a rare autosomal dominant condition caused by heterozygous variants in KIDINS220. A total of 12 individuals are reported, comprising eight with SINO and four with an autosomal recessive condition attributed to bi-allelic KIDINS220 variants.
METHODS: In our international cohort, we have comprised 14 individuals, carrying 13 novel pathogenic KIDINS220 variants in heterozygous form. We assessed clinical and molecular data of our cohort and previously reported individuals and based on functional experiments reached a better understanding of the pathogenesis behind KIDINS220-related disease.
RESULTS: Using fetal tissue and in vitro assays, we demonstrate that the variants generate KIDINS220 truncated forms that mislocalize in punctate intracellular structures, with decreased levels of the full-length protein, suggesting a trans-dominant negative effect. 92% had their diagnosis within three years, with symptoms of developmental delay, spasticity, hypotonia, lack of eye contact and nystagmus. We identified a KIDINS220 variant associated with fetal hydrocephalus and show that 58% of examined individuals present brain ventricular dilatation. We extend the phenotypic spectrum of SINO syndrome to behavioral manifestations not previously highlighted.
CONCLUSIONS: Our study provides further insights into the clinical spectrum, etiology and predicted functional impact of KIDINS220 variants.

Spastic paraplegia type 3A (SPG3A) is the second most common form of hereditary spastic paraplegia (HSP). This autosomal-dominant-inherited motor disorder is caused by heterozygous variants in the ATL1 gene which usually presents as a pure childhood-onset spastic paraplegia. Affected individuals present muscle weakness and spasticity in the lower limbs, with symptom onset in the first decade of life. Individuals with SPG3A typically present a slow progression and remain ambulatory throughout their life. Here we report three unrelated individuals presenting with very-early-onset (before 7 months) complex, and severe HSP phenotypes (axial hypotonia, spastic quadriplegia, dystonia, seizures and intellectual disability). For 2 of the 3 patients, these phenotypes led to the initial diagnosis of cerebral palsy (CP). These individuals carried novel ATL1 pathogenic variants (a de novo ATL1 missense p.(Lys406Glu), a homozygous frameshift p.(Arg403Glufs*3) and a homozygous missense variant (p.Tyr367His)). The parents carrying the heterozygous frameshift and missense variants were asymptomatic. Through these observations, we increase the knowledge on genotype-phenotype correlations in SPG3A and offer additional proof for possible autosomal recessive forms of SPG3A, while raising awareness on these exceptional phenotypes. Their ability to mimic CP also implies that genetic testing should be considered for patients with atypical forms of CP, given the implications for genetic counseling.

Variations in the UBQLN2 gene are associated with a group of diseases with X-linked dominant inheritance and clinical phenotypes of amyotrophic lateral sclerosis (ALS) and/or frontal temporal lobe dementia (FTD). Cases with UBQLN2 variations have been rarely reported worldwide. The reported cases exhibit strong clinical heterogeneity. Here, we report two adult-onset cases with UBQLN2 variations in Han Chinese. Whole exome sequencing revealed the hemizygous P506S (c.1516C > T) and the heterozygous P509S variation (c.1525C > T), both of which were located within the hotspot mutation region. The patient with the P506S variation was a 24-year-old male. The clinical feature was spastic paraplegia without lower motor neuron damage. The patient\'s mother was an asymptomatic heterozygote carrier with skewed X-chromosome inactivation. The patient with the P509S variation was a 63-year-old female. Clinical features included ALS and parkinsonism. 18F-fluorodopa PET-CT revealed presynaptic dopaminergic deficits in bilateral posterior putamen. These cases further highlight the clinical heterogeneity of UBQLN2 cases.

暂无摘要。

Spastic paraplegia and psychomotor retardation with or without seizures (SPPRS) is a rare neurodevelopmental disorder associated with autosomal recessive mutations in the HACE1 gene. This case report presents the clinical features and genetic analysis of an 11-month-old girl and her sister with SPPRS, making it the third reported case in the Middle East and the second in Saudi Arabia. The patient exhibited hypotonia, global developmental delay, speech delay, swallowing difficulties, and recurrent respiratory infections. A homozygous pathogenic variant in the HACE1 gene (p.R664*) was identified through genetic analysis, confirming the diagnosis of SPPRS. This case report emphasizes the importance of considering variations in clinical presentation, especially in rare disorders where only a few cases are reported. Further research and case studies are needed to better understand the complete phenotypic spectrum of SPPRS and its complications.

Motor neuron disorders comprise a clinically and pathologically heterogeneous group of neurologic diseases characterized by progressive degeneration of motor neurons (including both sporadic and hereditary diseases), affecting the upper motor neurons, lower motor neurons, or both. Hereditary motor neuron disorders themselves represent a vast and heterogeneous group, with numerous clinical and genetic overlaps that can be a source of error. This narrative review aims at providing an overview of the main types of inherited motor neuron disorders by recounting the stages in their historical descriptions. For practical purposes, this review of the literature sets out their various clinical characteristics and updates the list of all the genes involved in the various forms of inherited motor neuron disorders, including spinal muscular atrophy, familial amyotrophic lateral sclerosis, hereditary spastic paraplegia, distal hereditary motor neuropathies/neuronopathies, Kennedy\'s disease, riboflavin transporter deficiencies, VCPopathy and the neurogenic scapuloperoneal syndrome.

KIF1A-related disorders (KRDs) encompass recessive and dominant variants with wide clinical variability. Recent genetic investigations have expanded the clinical phenotypes of heterozygous KIF1A variants. However, there have been a few long-term observational studies of patients with heterozygous KIF1A variants. A retrospective chart review of consecutive patients diagnosed with spastic paraplegia at Miyagi Children\'s Hospital from 2016 to 2020 identified six patients with heterozygous KIF1A variants. To understand the long-term changes in clinical symptoms, we examined these patients in terms of their characteristics, clinical symptoms, results of electrophysiological and neuroimaging studies, and genetic testing. The median follow-up period was 30 years (4-44 years). This long-term observational study showed that early developmental delay and equinus gait, or unsteady gait, are the first signs of disease onset, appearing with the commencement of independent walking. In addition, later age-related progression was observed in spastic paraplegia, and the appearance of axonal neuropathy and reduced visual acuity were characteristic features of the late disease phenotype. Brain imaging showed age-related progression of cerebellar atrophy and the appearance of hyperintensity of optic radiation on T2WI and FLAIR imaging. Long-term follow-up revealed a pattern of steady progression and a variety of clinical symptoms, including spastic paraplegia, peripheral neuropathy, reduced visual acuity, and some degree of cerebellar ataxia. Clinical variability between patients was observed to some extent, and therefore, further studies are required to determine the phenotype-genotype correlation.

UNASSIGNED: The aim of this study is to provide a comprehensive characterization of a large Estonian family spanning five generations with seventeen individuals affected by spastic paraplegia associated with a novel variant in the receptor expression-enhancing protein-1 (REEP1) gene.
UNASSIGNED: Comprehensive clinical evaluation, neuroimaging, and neurophysiological studies were performed on six patients who provided oral and written consent. Whole-exome sequencing was performed on the index case. Targeted carrier testing was done in all other available affected and at-risk relatives.
UNASSIGNED: Four individuals presented with pure spastic paraplegia, with onset from early childhood to adult age. None had bladder or bowel dysfunction. Two subjectively asymptomatic mutation carriers displayed pyramidal signs on examination. Imaging of the neuroaxis was normal in three patients, three had MRI findings interpreted as unrelated. Motor evoked potential (MEP) was abnormal in five; the patient with the longest disease duration had additional somatosensory evoked potential (SSEP) abnormalities. The novel splice-site variant, c.32 + 1G > C in the REEP1 gene, found in the index case, co-segregates with disease in the family. Expressivity in this family is variable.
UNASSIGNED: Our findings are in keeping with previous descriptions of the SPG31 spectrum. The phenotype associated with splice variants is not necessarily more severe than other conventional REEP1 variants. As for other forms of familial spastic paraplegias, the factors modulating variable expressivity in SPG31 are still unknown.

Cells respond to lysosomal membrane permeabilization by membrane repair or selective macroautophagy of damaged lysosomes, termed lysophagy, but it is not fully understood how this decision is made. Here, we uncover a pathway in human cells that detects lipid bilayer perturbations in the limiting membrane of compromised lysosomes, which fail to be repaired, and then initiates ubiquitin-triggered lysophagy. We find that SPG20 binds the repair factor IST1 on damaged lysosomes and, importantly, integrates that with the detection of damage-associated lipid-packing defects of the lysosomal membrane. Detection occurs via sensory amphipathic helices in SPG20 before rupture of the membrane. If lipid-packing defects are extensive, such as during lipid peroxidation, SPG20 recruits and activates ITCH, which marks the damaged lysosome with lysine-63-linked ubiquitin chains to initiate lysophagy and thus triages the lysosome for destruction. With SPG20 being linked to neurodegeneration, these findings highlight the relevance of a coordinated lysosomal damage response for cellular homeostasis.

We herein report a case of VPS13D-related disorder with a novel homogeneous variant. A 58-year-old Japanese woman was referred to our hospital with slowly progressive gait disturbance and cognitive impairment. A neurological examination revealed decreased spontaneity, recent memory impairment, Parkinsonism, cerebellar ataxia, pyramidal signs, and autonomic dysfunction. Dopamine transporter single-photon-emission computed tomography showed a markedly reduced uptake in the striatum bilaterally. Whole-exome sequencing revealed a novel homozygous missense variant of the VPS13D gene (Arg3267Pro). Our case suggests that mutations in VPS13D may cause parkinsonism, in addition to the previously reported cerebellar ataxia and spastic paraplegia.