RARE DISEASE
Autosomal recessive spastic ataxia of Charlevoix-Saguenay
Autosomal recessive spastic ataxia of Charlevoix-Saguenay
Autosomal recessive spastic ataxia of Charlevoix-Saguenay
Synonyms: ARSACS, Autosomal recessive spastic ataxia type 6, SPAX6
Synonyms: ARSACS, Autosomal recessive spastic ataxia type 6, SPAX6
Synonyms: ARSACS, Autosomal recessive spastic ataxia type 6, SPAX6
Drug discovery
0
drugs
With orphan designations
Overview
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a rare neurodegenerative disorder caused by SACS gene mutations, characterized by early-onset cerebellar ataxia (12-24 months), progressive spasticity, axonal neuropathy, and retinal hypermyelination. Disease progression leads to wheelchair dependence by age 30-40, with life expectancy typically extending to the sixth decade. Diagnosis combines clinical triad (ataxia, spasticity, neuropathy), neuroimaging (cerebellar/pontine atrophy), and genetic confirmation [1][6][11].
Burden
Functional decline: 100% require wheelchairs by mid-adulthood; 50% develop academic struggles despite normal cognition [3][12].
Economic impact: Requires lifelong specialized care, adaptive devices, and caregiver support [16][17].
Mortality: Median survival ~60 years, with complications from immobility contributing to morbidity [3][6].
Categories: rare genetic diseases, rare neurological diseases
Research Papers
50 drug discovery papers about Autosomal recessive spastic ataxia of Charlevoix-Saguenay, with 1 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
50 drug discovery papers about Autosomal recessive spastic ataxia of Charlevoix-Saguenay, with 1 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
2026-06-15 | Loss of SARM1 Improves Phenotypes in a Mouse Model of Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay.
Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) is a neurodegenerative disease caused by pathogenic variants in SACS. ARSACS is characterized by mitochondrial abnormalities and disruptions of the neurofilament cytoskeleton. In other conditions, these features have been linked to activation of Sterile Alpha and TIR Motif Containing 1 (SARM1), an enzyme that can trigger axon degeneration and neuronal death. Inhibition of SARM1 is an attractive therapeutic strategy because SARM1 is inactive in healthy cells and knockout of SARM1 has little or no deleterious effects. We therefore asked whether SARM1 activity contributed to Purkinje cell degeneration and motor defects present in a Sacs -/- mouse model of ARSACS. We studied 4 cohorts of mice: (1) Sacs -/- ; Sarm1 +/+ ; (2) Sacs +/+ ; Sarm1 +/- ; (3) Sacs -/- ; Sarm1 +/- ; and (4) Sacs -/- ; Sarm1 -/- . In 9-month-old mice, we analyzed protein markers of Purkinje cells (n = 3-4 mice per genotype) and counted surviving Purkinje cells in folia III, IV, and VIII of cerebellar sections (n = 3 mice per genotype, 6 sections per mouse), and tested motor function at 3, 6, and 9 months by quantifying parameters of gait (Digigait) and coordination and balance (Rotarod) (8 male, 8 female mice of each genotype). Probing of cerebellar extracts showed that the Purkinje cell protein markers Calbindin-1, RGS8, and PCP2 were decreased in Sacs -/- mice but restored to normal levels in Sacs -/- ; Sarm1 -/- mice. Purkinje cell loss in Sacs -/- mice was most prominent in anterior folia, as previously noted. Sarm1 loss partially mitigated the Purkinje cell death in folium III of 9-month-old Sacs -/- mice. Similarly, longitudinal behavioral assessment of motor functions showed that disturbances in gait pattern (slower cadence, prolonged swing, and stance phases) were partially alleviated. Rotarod tests gave more ambivalent results, as the homozygous loss of Sarm1 was less effective than heterozygous loss in ameliorating the Sacs -/- phenotype. We conclude that SARM1 contributes to neurodegeneration in ARSACS, and its downregulation or inhibition could constitute a significant therapeutical strategy in the treatment of the disease.
2025-12-07 | Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay in Two Half-Siblings.
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is caused by biallelic pathogenic variants in the SACS gene. We report the clinical, radiologic and neurophysiologic features of a pair of half-siblings who presented with progressive cerebellar ataxia, peripheral neuropathy and upper motor neuron signs. After significant diagnostic delay, genetic testing revealed both harboured a shared, paternally inherited microdeletion encompassing the SACS gene, and each harboured a different single nucleotide variant in SACS, each likely maternally inherited. Recognition of the clinical and radiologic phenotype of ARSACS may facilitate early diagnosis of this disorder even in the face of uncommon inheritance patterns.
2025-09-29 | Novel SACS Variants not Recorded in ClinVar Identified in a Chinese Patient with Late-Onset Hereditary Neuropathy: a Case Report and Literature Review.
Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) is a rare neurodegenerative disorder due to mutations in the SACS gene. While the typical phenotype is characterized by cerebellar ataxia, spasticity, and peripheral neuropathy, more reports are published of atypical and late-onset presentations, also lacking typical cerebellar signs of the disease, which can mimic Charcot-Marie-Tooth disease (CMT). We report a 58-year-old Chinese male with a 12-year history of progressive gait instability and lower limb weakness, who also exhibited retinal degeneration. Remarkably, in contrast to the majority of ARSACS patients, he had no significant spasticity, thus expanding the phenotypic spectrum. Genetic analysis identified a pathogenic compound heterozygous mutation in SACS: a novel frameshift variant (c.178del, p.Asp60ThrfsTer8) in exon 4, unreported in ClinVar, and a missense variant (c.4723 C > T, p.Arg1575Trp) in exon 10, documented in ClinVar with conflicting interpretations. The exceptionally late onset in this patient suggests that the c.178del frameshift may partially preserve sacsin function, thereby delaying disease manifestation. MLPA analysis excluded CMT1/HNPP-related rearrangements, confirming an ARSACS diagnosis. Familial segregation further supported autosomal recessive inheritance, emphasizing the importance of family screening. Given this, our case suggests a potential extended therapeutic window in late-onset ARSACS and may need to be included in future therapeutics efforts, emphasizing the importance of identifying such atypical forms. This observation highlights the importance of thorough genetic testing in achieving a correct diagnosis and providing treatment for patients with undiagnosed progressive ataxia.
2025-08-05 | A Pharmacometrics-Informed Trial Simulation Framework for Optimizing Study Designs for Disease-Modifying Treatments in Rare Neurological Disorders.
The development of new treatments for rare neurological diseases (RNDs) may be very challenging due to limited natural history data, lack of relevant biomarkers and clinical endpoints, small and heterogeneous patient populations, and other complexities. A systematic approach is needed for comparing various design and analysis strategies to identify "optimal" approaches for a clinical trial in a chosen RND with the given resource constraints. For this purpose, we propose a pharmacometrics-informed clinical scenario evaluation framework (CSE-PMx), which includes some important research hallmarks relevant to RND clinical trials: a disease progression model for simulating individual longitudinal outcomes, the choice of a suitable randomization method for trial design, and an option to perform subsequent statistical analysis with randomization tests. We illustrate the utility of CSE-PMx for an exemplary randomized trial to compare the disease-modifying effect of an experimental treatment versus control in patients with Autosomal-Recessive Spastic Ataxia Charlevoix Saguenay (ARSACS). In the considered example, our simulation evidence suggests that a nonlinear mixed-effects model (NLMEM) with a population-based likelihood ratio test analysis is valid, robust, and more powerful than some conventional methods such as two-sample t-test, analysis of covariance (ANCOVA), or a mixed model with repeated measurements (MMRM). Our proposed framework is very flexible and generalizable to clinical research in other rare disease indications.
2025-05-04 | Genetic analysis of three patients from two unrelated Chinese families with autosomal recessive spastic ataxia of Charlevoix-Saguenay.
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a rare early-onset neurodegenerative disorder characterized by progressive cerebellar ataxia, spasticity, and sensorimotor peripheral neuropathy. This disorder is caused by homozygous or compound heterozygous variants in the sacsin (SACS) gene on chromosome 13q12.12. Three patients with ARSACS from two unrelated Chinese families were recruited for this study. Patient #1 was an 18-year-old male who had been walking unstably for 12 years. Patient #2, the younger sister of Patient #1, was a 5-year-old girl who had been walking unstably for 2 years. Patient #3 was a 19-year-old female who had been walking unstably and a tendency to fall for 17 years. For Patient #1, whole-exome sequencing (WES) identified a hemizygous variant c.8310_8313delAGAT (p.Asp2771fs4*) in SACS (NM_014363.6), with the father being heterozygous, the mother wild-type, and Patient #2 hemizygous, as verified by Sanger sequencing. Additional copy number variant analysis of the WES data indicated that Patient #1 had a heterozygous gross deletion of chr13q12.12 (chr13:23,808,732 - 24,890,322). Low-coverage whole-genome sequencing results revealed that Patient #2 carried a chr13q12.12 deletion (chr13:23,520,000-24,940,000). Together with Sanger sequencing results, this gross deletion was speculated to have been inherited from the mother, further explaining the hemizygous state of c.8310_8313delAGAT (p.Asp2771fs4*) in Patients #1 and #2. Through WES, Patient #3 was identified as having suspected compound heterozygous variants of c.2881 C > T (p.Arg961*) and c.6409 C > T (p.Gln2137*), inherited from the father and mother, respectively, as confirmed by Sanger sequencing. This study identified three variants in SACS. The c.8310_8313delAGAT (p.Asp2771fs4*) is novel, whereas c.2881 C > T (p.Arg961*) and c.6409 C > T (p.Gln2137*) have been reported previously. Moreover, this study highlights the growing trend that ARSACS has become increasingly prevalent worldwide rather than being localized to a specific region or race. As an increasing number of patients with ARSACS are diagnosed, the genetic spectrum of ARSACS will gradually broaden, providing an accurate genetic basis for prenatal diagnosis of mothers in the years ahead, if possible.
2026-06-15 | Loss of SARM1 Improves Phenotypes in a Mouse Model of Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay.
Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) is a neurodegenerative disease caused by pathogenic variants in SACS. ARSACS is characterized by mitochondrial abnormalities and disruptions of the neurofilament cytoskeleton. In other conditions, these features have been linked to activation of Sterile Alpha and TIR Motif Containing 1 (SARM1), an enzyme that can trigger axon degeneration and neuronal death. Inhibition of SARM1 is an attractive therapeutic strategy because SARM1 is inactive in healthy cells and knockout of SARM1 has little or no deleterious effects. We therefore asked whether SARM1 activity contributed to Purkinje cell degeneration and motor defects present in a Sacs -/- mouse model of ARSACS. We studied 4 cohorts of mice: (1) Sacs -/- ; Sarm1 +/+ ; (2) Sacs +/+ ; Sarm1 +/- ; (3) Sacs -/- ; Sarm1 +/- ; and (4) Sacs -/- ; Sarm1 -/- . In 9-month-old mice, we analyzed protein markers of Purkinje cells (n = 3-4 mice per genotype) and counted surviving Purkinje cells in folia III, IV, and VIII of cerebellar sections (n = 3 mice per genotype, 6 sections per mouse), and tested motor function at 3, 6, and 9 months by quantifying parameters of gait (Digigait) and coordination and balance (Rotarod) (8 male, 8 female mice of each genotype). Probing of cerebellar extracts showed that the Purkinje cell protein markers Calbindin-1, RGS8, and PCP2 were decreased in Sacs -/- mice but restored to normal levels in Sacs -/- ; Sarm1 -/- mice. Purkinje cell loss in Sacs -/- mice was most prominent in anterior folia, as previously noted. Sarm1 loss partially mitigated the Purkinje cell death in folium III of 9-month-old Sacs -/- mice. Similarly, longitudinal behavioral assessment of motor functions showed that disturbances in gait pattern (slower cadence, prolonged swing, and stance phases) were partially alleviated. Rotarod tests gave more ambivalent results, as the homozygous loss of Sarm1 was less effective than heterozygous loss in ameliorating the Sacs -/- phenotype. We conclude that SARM1 contributes to neurodegeneration in ARSACS, and its downregulation or inhibition could constitute a significant therapeutical strategy in the treatment of the disease.
2025-12-07 | Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay in Two Half-Siblings.
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is caused by biallelic pathogenic variants in the SACS gene. We report the clinical, radiologic and neurophysiologic features of a pair of half-siblings who presented with progressive cerebellar ataxia, peripheral neuropathy and upper motor neuron signs. After significant diagnostic delay, genetic testing revealed both harboured a shared, paternally inherited microdeletion encompassing the SACS gene, and each harboured a different single nucleotide variant in SACS, each likely maternally inherited. Recognition of the clinical and radiologic phenotype of ARSACS may facilitate early diagnosis of this disorder even in the face of uncommon inheritance patterns.
2025-09-29 | Novel SACS Variants not Recorded in ClinVar Identified in a Chinese Patient with Late-Onset Hereditary Neuropathy: a Case Report and Literature Review.
Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) is a rare neurodegenerative disorder due to mutations in the SACS gene. While the typical phenotype is characterized by cerebellar ataxia, spasticity, and peripheral neuropathy, more reports are published of atypical and late-onset presentations, also lacking typical cerebellar signs of the disease, which can mimic Charcot-Marie-Tooth disease (CMT). We report a 58-year-old Chinese male with a 12-year history of progressive gait instability and lower limb weakness, who also exhibited retinal degeneration. Remarkably, in contrast to the majority of ARSACS patients, he had no significant spasticity, thus expanding the phenotypic spectrum. Genetic analysis identified a pathogenic compound heterozygous mutation in SACS: a novel frameshift variant (c.178del, p.Asp60ThrfsTer8) in exon 4, unreported in ClinVar, and a missense variant (c.4723 C > T, p.Arg1575Trp) in exon 10, documented in ClinVar with conflicting interpretations. The exceptionally late onset in this patient suggests that the c.178del frameshift may partially preserve sacsin function, thereby delaying disease manifestation. MLPA analysis excluded CMT1/HNPP-related rearrangements, confirming an ARSACS diagnosis. Familial segregation further supported autosomal recessive inheritance, emphasizing the importance of family screening. Given this, our case suggests a potential extended therapeutic window in late-onset ARSACS and may need to be included in future therapeutics efforts, emphasizing the importance of identifying such atypical forms. This observation highlights the importance of thorough genetic testing in achieving a correct diagnosis and providing treatment for patients with undiagnosed progressive ataxia.
2025-08-05 | A Pharmacometrics-Informed Trial Simulation Framework for Optimizing Study Designs for Disease-Modifying Treatments in Rare Neurological Disorders.
The development of new treatments for rare neurological diseases (RNDs) may be very challenging due to limited natural history data, lack of relevant biomarkers and clinical endpoints, small and heterogeneous patient populations, and other complexities. A systematic approach is needed for comparing various design and analysis strategies to identify "optimal" approaches for a clinical trial in a chosen RND with the given resource constraints. For this purpose, we propose a pharmacometrics-informed clinical scenario evaluation framework (CSE-PMx), which includes some important research hallmarks relevant to RND clinical trials: a disease progression model for simulating individual longitudinal outcomes, the choice of a suitable randomization method for trial design, and an option to perform subsequent statistical analysis with randomization tests. We illustrate the utility of CSE-PMx for an exemplary randomized trial to compare the disease-modifying effect of an experimental treatment versus control in patients with Autosomal-Recessive Spastic Ataxia Charlevoix Saguenay (ARSACS). In the considered example, our simulation evidence suggests that a nonlinear mixed-effects model (NLMEM) with a population-based likelihood ratio test analysis is valid, robust, and more powerful than some conventional methods such as two-sample t-test, analysis of covariance (ANCOVA), or a mixed model with repeated measurements (MMRM). Our proposed framework is very flexible and generalizable to clinical research in other rare disease indications.
2025-05-04 | Genetic analysis of three patients from two unrelated Chinese families with autosomal recessive spastic ataxia of Charlevoix-Saguenay.
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a rare early-onset neurodegenerative disorder characterized by progressive cerebellar ataxia, spasticity, and sensorimotor peripheral neuropathy. This disorder is caused by homozygous or compound heterozygous variants in the sacsin (SACS) gene on chromosome 13q12.12. Three patients with ARSACS from two unrelated Chinese families were recruited for this study. Patient #1 was an 18-year-old male who had been walking unstably for 12 years. Patient #2, the younger sister of Patient #1, was a 5-year-old girl who had been walking unstably for 2 years. Patient #3 was a 19-year-old female who had been walking unstably and a tendency to fall for 17 years. For Patient #1, whole-exome sequencing (WES) identified a hemizygous variant c.8310_8313delAGAT (p.Asp2771fs4*) in SACS (NM_014363.6), with the father being heterozygous, the mother wild-type, and Patient #2 hemizygous, as verified by Sanger sequencing. Additional copy number variant analysis of the WES data indicated that Patient #1 had a heterozygous gross deletion of chr13q12.12 (chr13:23,808,732 - 24,890,322). Low-coverage whole-genome sequencing results revealed that Patient #2 carried a chr13q12.12 deletion (chr13:23,520,000-24,940,000). Together with Sanger sequencing results, this gross deletion was speculated to have been inherited from the mother, further explaining the hemizygous state of c.8310_8313delAGAT (p.Asp2771fs4*) in Patients #1 and #2. Through WES, Patient #3 was identified as having suspected compound heterozygous variants of c.2881 C > T (p.Arg961*) and c.6409 C > T (p.Gln2137*), inherited from the father and mother, respectively, as confirmed by Sanger sequencing. This study identified three variants in SACS. The c.8310_8313delAGAT (p.Asp2771fs4*) is novel, whereas c.2881 C > T (p.Arg961*) and c.6409 C > T (p.Gln2137*) have been reported previously. Moreover, this study highlights the growing trend that ARSACS has become increasingly prevalent worldwide rather than being localized to a specific region or race. As an increasing number of patients with ARSACS are diagnosed, the genetic spectrum of ARSACS will gradually broaden, providing an accurate genetic basis for prenatal diagnosis of mothers in the years ahead, if possible.
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