New cases of adult-onset Sandhoff disease with a cerebellar or lower motor neuron phenotype

Innate immune sensing of lysosomal dysfunction drives multiple lysosomal storage disorders

Lysosomal storage disorders (LSDs), which are characterized by genetic and metabolic lysosomal dysfunctions, constitute over 60 degenerative diseases with considerable health and economic burdens. However, the mechanisms driving the progressive death of functional cells due to lysosomal defects remain incompletely understood, and broad-spectrum therapeutics against LSDs are lacking. Here, we found that various gene abnormalities that cause LSDs, including Hexb, Gla, Npc1, Ctsd and Gba, all shared mutual properties to robustly autoactivate neuron-intrinsic cGAS-STING signalling, driving neuronal death and disease progression. This signalling was triggered by excessive cytoplasmic congregation of the dsDNA and DNA sensor cGAS in neurons. Genetic ablation of cGAS or STING, digestion of neuronal cytosolic dsDNA by DNase, and repair of neuronal lysosomal dysfunction alleviated symptoms of Sandhoff disease, Fabry disease and Niemann-Pick disease, with substantially reduced neuronal loss. We therefore identify a ubiquitous mechanism mediating the pathogenesis of a variety of LSDs, unveil an inherent connection between lysosomal defects and innate immunity, and suggest a uniform strategy for curing LSDs.

Clinical and genetic features of a case with juvenile onset sandhoff disease

BACKGROUND

Sandhoff disease (SD) is a rare neurological disease with high clinical heterogeneity. SD in juvenile form is much rarer and it is often misdiagnosed in clinics. Therein, it is necessary to provide more cases and review the literature on juvenile onset SD.

CASE PRESENTATION

A 14 years-old boy with eight years of walking difficulties, and was ever misdiagnosed as spinocerebellar ataxia. We found this patient after genetic testing carried rs201580118 and a novel gross deletion in HEXB (g.74012742_74052694del). Through review the literature, we found that was the first gross deletion identified at the 3'end of HEXB, associated with juvenile onset SD from China.

CONCLUSION

This case expanded our knowledge about the genotype and phenotype correlations in SD. Comprehensive genetic testing is important for the diagnosis of unexplained ataxia.

A 23-year follow-up report of juvenile-onset Sandhoff disease presenting with a motor neuron disease phenotype and a novel variant

BACKGROUND

The clinical severity of Sandhoff disease is known to vary widely. Furthermore, long-term follow-up report is very limited in the literature.

CASE PRESENTATION

We present a long-term follow-up report of a patient with juvenile-onset Sandhoff disease with a motor neuron disease phenotype. The patient had compound heterozygous variants of HEXB (p.Trp460Arg, p. Arg533His); the Trp460Arg was a novel variant. Long-term follow-up revealed no intellectual deterioration, swallowing dysfunction, or respiratory muscle dysfunction despite progressive weakness of the extremities and sensory disturbances.

CONCLUSION

We need to be aware of Sandhoff disease in patients with juvenile-onset motor neuron disease.

Natural history of Tay-Sachs disease in sheep

Tay-Sachs disease (TSD) is a fatal neurodegenerative disease caused by a deficiency of the enzyme β-N-acetylhexosaminidase A (HexA). TSD naturally occurs in Jacob sheep is the only experimental model of TSD. TSD in sheep recapitulates neurologic features similar to juvenile onset and late onset TSD patients. Due to the paucity of human literature on pathology of TSD, a better natural history in the sheep TSD brain, which is on the same order of magnitude as a child's, is necessary for evaluating therapy and characterizing the pathological events that occur. To provide clinicians and researchers with a clearer understanding of longitudinal pathology in patients, we compare spectrum of clinical signs and brain pathology in mildly symptomatic (3-months), moderately symptomatic (6-months), or severely affected TSD sheep (humane endpoint at ~9-months of age). Increased GM2 ganglioside in the CSF of TSD sheep and a TSD specific biomarker on MRS (taurine) correlate with disease severity. Microglial activation and reactive astrocytes were observed globally on histopathology in TSD sheep with a widespread reduction in oligodendrocyte density. Myelination is reduced primarily in the forebrain illustrated by loss of white matter on MRI. GM2 and GM3 ganglioside were increased and distributed differently in various tissues. The study of TSD in the sheep model provides a natural history to shed light on the pathophysiology of TSD, which is of utmost importance due to novel therapeutics being assessed in human patients.

Magnetic resonance imaging and spectroscopy in late-onset GM2-gangliosidosis

OBJECTIVE

Our study aimed to quantify structural changes in relation to metabolic abnormalities in the cerebellum, thalamus, and parietal cortex of patients with late-onset GM2-gangliosidosis (LOGG), which encompasses late-onset Tay-Sachs disease (LOTS) and Sandhoff disease (LOSD).

METHODS

We enrolled 10 patients with LOGG (7 LOTS, 3 LOSD) who underwent a neurological assessment battery and 7 age-matched controls. Structural MRI and MRS were performed on a 3 T scanner. Structural volumes were obtained from FreeSurfer and normalized by total intracranial volume. Quantified metabolites included N-acetylaspartate (NAA), choline (Cho), myo-inositol (mI), creatine (Cr), and combined glutamate-glutamine (Glx). Metabolic concentrations were corrected for partial volume effects.

RESULTS

Structural analyses revealed significant cerebellar atrophy in the LOGG cohort, which was primarily driven by LOTS patients. NAA was lower and mI higher in LOGG, but this was also significantly driven by the LOTS patients. Clinical ataxia deficits (via the Scale for the Assessment and Rating of Ataxia) were associated with neuronal injury (via NAA), neuroinflammation (via mI), and volumetric atrophy in the cerebellum.

INTERPRETATION

The decrease of NAA in the cerebellum suggests that, in addition to cerebellar atrophy, there is ongoing impaired neuronal function and/or loss, while an increase in mI indicates possible neuroinflammation in LOGG (more so within the LOTS subvariant). Quantifying cerebellar atrophy in relation to neurometabolic differences in LOGG may lead to improvements in assessing disease severity, progression, and pharmacological efficacy. Lastly, additional neuroimaging studies in LOGG are required to contrast LOTS and LOSD more accurately.

Late onset Sandhoff disease presenting with lower motor neuron disease and stuttering

Defects in the HEXB gene which encodes the β-subunit of β-hexosaminidase A and B enzymes, cause a GM2 gangliosidosis, also known as Sandhoff disease, which is a rare lysosomal storage disorder. The most common form of the disease lead to quickly progressing mental and motor decline in infancy; however there are other less severe forms with later onset that can also involve lower motor neurons. The diagnosis of this disease is based on low serum β-hexosaminidases A and B levels and confirmed using genetic test. We report two siblings with compound heterozygous HEXB mutations whose phenotype was extremely mild consisting in stuttering in both cases associated to mild proximal weakness in one of the cases, broadening the clinical spectrum of late onset Sandhoff disease.

Sandhoff disease in the elderly: a case study

Sandhoff disease is an infrequent, genetically caused disorder with a recessive autosomal inheritance pattern. It belongs to the gangliosidosis GM2 group and is produced by mutations in gen HEXB leading to reduction in enzymatic activity of enzymes β-hexosaminidase A and B. Adult-onset GM2 gangliosidosis is rare. Here we report a white male who presented at age 69 with a fast-progression, motor neuron disease, mimicking amyotrophic lateral sclerosis (ALS), combined with autonomic dysfunction, sensory ataxia, and exaggerated startle to noise. Enzymatic assays demonstrated deficiency of both Hexosaminidases A and B leading to the diagnosis of Sandhoff disease.

Natural History of Adult Patients with GM2 Gangliosidosis

OBJECTIVE

GM2 gangliosidoses are lysosomal diseases due to biallelic mutations in the HEXA (Tay-Sachs disease [TS]) or HEXB (Sandhoff disease [SD]) genes, with subsequent low hexosaminidase(s) activity. Most patients have childhood onset, but some experience the first symptoms during adolescence/adulthood. This study aims to clarify the natural history of adult patients with GM2 gangliosidosis.

METHODS

We retrospectively described 12 patients from a French cohort and 45 patients from the literature.

RESULTS

We observed 4 typical presentations: (1) lower motoneuron disorder responsible for proximal lower limb weakness that subsequently expanded to the upper limbs, (2) cerebellar ataxia, (3) psychosis and/or severe mood disorder (only in the TS patients), and (4) a complex phenotype mixing the above 3 manifestations. The psoas was the first and most affected muscle in the lower limbs, whereas the triceps and interosseous were predominantly involved in the upper limbs. A longitudinal study of compound motor action potentials showed a progressive decrease in all nerves, with different kinetics. Sensory potentials were sometimes abnormally low, mainly in the SD patients. The main brain magnetic resonance imaging feature was cerebellar atrophy, even in patients without cerebellar symptoms. The prognosis was mainly related to gait disorder, as we showed that beyond 20 years of disease evolution, half of the patients were wheelchair users.

INTERPRETATION

Improved knowledge of GM2 gangliosidosis in adults will help clinicians achieve correct diagnoses and better inform patients on the evolution and prognosis. It may also contribute to defining proper outcome measures when testing emerging therapies. ANN NEUROL 2020;87:609-617.

Quantitative oculomotor and nonmotor assessments in late-onset GM2 gangliosidosis

OBJECTIVE

A cross-sectional study was performed to evaluate whether quantitative oculomotor measures correlate with disease severity in late-onset GM2 gangliosidosis (LOGG) and assess cognition and sleep as potential early nonmotor features.

METHODS

Ten patients with LOGG underwent quantitative oculomotor recordings, including measurements of the angular vestibulo-ocular reflex (VOR), with results compared to age- and sex-matched controls. Disease severity was assessed by ataxia rating scales. Cognitive/neuropsychiatric features were assessed by the cerebellar cognitive affective syndrome (CCAS) scale, Cerebellar Neuropsychiatric Rating Scale, and sleep quality evaluated using subjective sleep scales.

RESULTS

Oculomotor abnormalities were found in all participants, including 3/10 with clinically normal eye movements. Abnormalities involved impaired saccadic accuracy (5/10), abnormal vertical (8/10) and horizontal (4/10) pursuit, reduced optokinetic nystagmus (OKN) responses (7/10), low VOR gain (10/10), and impaired VOR cancellation (2/10). Compared to controls, the LOGG group showed significant differences in saccade, VOR, OKN, and visually enhanced VOR gains. Severity of saccadic dysmetria, OKN, and VOR fixation-suppression impairments correlated with ataxia scales (p < 0.05). Nine out of ten patients with LOGG had evidence of the CCAS (5/10 definite, 2/10 probable, 2/10 possible). Excessive daytime sleepiness was present in 4/10 and 8/10 had poor subjective sleep quality.

CONCLUSIONS

Cerebellar oculomotor abnormalities were present in all patients with LOGG, including those with normal clinical oculomotor examinations. Saccade accuracy (dorsal cerebellar vermis localization), fixation suppression, and OKN gain (cerebellar flocculus/paraflocculus localization) correlated with disease severity, suggesting that quantitative oculomotor measurements could be used to track disease progression. We found evidence of the CCAS, suggesting that cerebellar dysfunction may explain the cognitive disorder in LOGG. Sleep impairments were prevalent and require further study.

Emerging links between pediatric lysosomal storage diseases and adult parkinsonism

Lysosomal storage disorders comprise a clinically heterogeneous group of autosomal-recessive or X-linked genetic syndromes caused by disruption of lysosomal biogenesis or function resulting in accumulation of nondegraded substrates. Although lysosomal storage disorders are diagnosed predominantly in children, many show variable expressivity with clinical presentations possible later in life. Given the important role of lysosomes in neuronal homeostasis, neurological manifestations, including movement disorders, can accompany many lysosomal storage disorders. Over the last decade, evidence from genetics, clinical epidemiology, cell biology, and biochemistry have converged to implicate links between lysosomal storage disorders and adult-onset movement disorders. The strongest evidence comes from mutations in Glucocerebrosidase, which cause Gaucher's disease and are among the most common and potent risk factors for PD. However, recently, many additional lysosomal storage disorder genes have been similarly implicated, including SMPD1, ATP13A2, GALC, and others. Examination of these links can offer insight into pathogenesis of PD and guide development of new therapeutic strategies. We systematically review the emerging genetic links between lysosomal storage disorders and PD. © 2019 International Parkinson and Movement Disorder Society.

Motor neuron disease in inherited neurometabolic disorders

Inherited neurometabolic disorders represent a growing group of inborn errors of metabolism that present with major neurological symptoms or a complex spectrum of symptoms dominated by central or peripheral nervous system dysfunction. Many neurological presentations may arise from the same metabolic defect, especially in autosomal-recessive inherited disorders. Motor neuron disease (MND), mainly represented by amyotrophic lateral sclerosis, may also result from various inborn errors of metabolism, some of which may represent potentially treatable conditions, thereby emphasizing the importance of recognizing such diseases. The present review discusses the most important neurometabolic disorders presenting with motor neuron (lower and/or upper) dysfunction as the key clinical and neuropathological feature.

Peripheral neuropathy in complex inherited diseases: an approach to diagnosis

Peripheral neuropathy is a common finding in patients with complex inherited neurological diseases and may be subclinical or a major component of the phenotype. This review aims to provide a clinical approach to the diagnosis of this complex group of patients by addressing key questions including the predominant neurological syndrome associated with the neuropathy, for example, spasticity, the type of neuropathy and the other neurological and non-neurological features of the syndrome. Priority is given to the diagnosis of treatable conditions. Using this approach, we associated neuropathy with one of three major syndromic categories: (1) ataxia, (2) spasticity and (3) global neurodevelopmental impairment. Syndromes that do not fall easily into one of these three categories can be grouped according to the predominant system involved in addition to the neuropathy, for example, cardiomyopathy and neuropathy. We also include a separate category of complex inherited relapsing neuropathy syndromes, some of which may mimic Guillain-Barré syndrome, as many will have a metabolic aetiology and be potentially treatable.

An Infantile Case of Sandhoff Disease Presenting With Swallowing Difficulty

Infants with Sandhoff disease typically appear normal until 3–6 months of age. As the disease progresses, they present with symptoms such as loss of motor skills, exaggerated startle response to loud noise, seizures, visual loss, and paralysis. We encountered a rare case of a 22-month-old girl with Sandhoff disease characterized by progressive motor weakness and dysphagia, who initially showed signs of aspiration at 20 months of age. The major problems related to dysphagia were oromotor dysfunction and abnormal feeding posture. Within 3 months of identification of difficulty in swallowing, the patient showed a significant decrease in food intake, with rapid deterioration of nutritional status. We report our case with a review of the literature.

Clinical,biochemical and molecular analysis of five Chinese patients with Sandhoff disease

Sandhoff disease (SD) is a rare autosomal recessive lysosomal storage disorder of sphingolipid metabolism resulting from the deficiency of β-hexosaminidase (HEX). Mutations of the HEXB gene cause Sandhoff disease. In order to improve the diagnosis and expand the knowledge of the disease, we collected and analyzed relevant data of clinical diagnosis, biochemical investigation, and molecular mutational analysis in five Chinese patients with SD. The patients presented with heterogenous symptoms of neurologic deterioration. HEX activity in leukocytes was severely deficient. We identified seven different mutations, including three known mutations: IVS12-26G > A, p.T209I, p.I207V, and four novel mutations: p.P468PfsX62, p.L223P, p.Y463X, p.G549R. We also detected two different heterozygous mutations c.-122delC and c.-126C > T in the promoter which were suspected to be deleterious mutations. We attempted to correlate these mutations with the clinical presentation of the patients. Our study indicates that the mutation p.T209I and p.P468PfsX62 may link to the infantile form of SD. Our study expands the spectrum of genotype of SD in China, provides new insights into the molecular mechanism of SD and helps to the diagnosis and treatment of this disease.

Natural history of motor neuron disease in adult onset GM2-gangliosidosis: A case report with 25 years of follow-up

An adult with Sandhoff disease presented with pure lower motor neuron phenotype. Twenty years later, he showed signs of upper motor neuron involvement. 25 years from the onset, his muscle weakness slightly worsened but he was fully independent in activities of daily living.

GM2-gangliosidosis can manifest as a motor neuron disease with a slowly progressive course. The correct knowledge of the natural history can be really important to achieve the diagnosis, design new therapies and evaluate clinical trials.

Atypical presentation of late-onset Tay-Sachs disease

INTRODUCTION

Late-onset Tay-Sachs disease (LOTS) is a lysosomal storage disease caused by deficient Beta-hexosaminidase A activity.

METHODS

We describe a 53-year-old woman who presented with adult-onset leg weakness, and whose initial diagnosis was progressive muscular atrophy without identifiable etiology. Development of cerebellar ataxia in mid-life prompted reassessment.

RESULTS

Beta-hexosaminidase A quantification assay demonstrated absence of the isozyme. Genetic testing identified compound heterozygous mutations in the HEXA gene, confirming the diagnosis of LOTS.

CONCLUSIONS

The phenotypic spectrum of LOTS includes motor neuronopathy, ataxia, choreoathetosis, neuropathy, and psychiatric symptoms in various combinations. This patient highlights the emergence of different clinical features over many years and emphasizes the need to consider LOTS in the differential diagnosis of progressive muscular atrophy.

Adult Sandhoff disease with 2 mutations in the HEXB gene presenting as brachial amyotrophic diplegia

Sandhoff disease is a rare autosomal recessive metabolic disorder of GM2 gangliosides. It is caused by a lack of functional N-acetyl-β-D-glucosaminidase A and B because of mutations in the HEXB gene. We describe a 55-year-old woman with adult Sandhoff disease presenting as brachial amyotrophic diplegia. The assay of total hexosaminidase involving A and B showed decreased level of these activities. Hex-A was 4.6 nmol·min·mL (normal: 7.0-20.0 nmol·min·mL) and Hex-B was 0.1 nmol·min·mL (normal: 1.0-10.0 nmol·min·mL), respectively. Analysis of HEXB gene demonstrated 2 point mutations that were located at the exon 5 (c.619A>G) and exon 11 (c.1250C>T). Compound heterozygosity of these 2 mutations may trigger the development of distinct adult Sandhoff disease phenotype. Sandhoff disease should be considered in the differential diagnosis of lower motor neuron disease, such as brachial amyotrophic diplegia, even if the age at onset is more than 50 years.

Characterization of the mutant β-subunit of β-hexosaminidase for dimer formation responsible for the adult form of Sandhoff disease with the motor neuron disease phenotype

The adult form of Sandhoff disease with the motor neuron disease phenotype is a rare neurodegenerative disorder caused by mutations in HEXB encoding the β-subunit of β-hexosaminidase, yet the properties of mutant β-subunits of the disease have not been fully determined. We identified a novel mutation (H235Y) in the β-sheet of the (β/α)₈-barrel domain, in addition to the previously reported P417L mutation that causes aberrant splicing, in a Japanese patient with the motor neuron disease phenotype. Enzyme assays, gel filtration studies and immunoprecipitation studies with HEK293 cells transiently expressing mutant β-subunits demonstrated that the H235Y mutation abolished both α-β and β-β dimer formation without increasing β-hexosaminidase activity, whereas other reported mutant β-subunits (Y456S, P504S or R533H) associated with the motor neuron disease phenotype formed dimers. Structural analysis suggested that the H235Y mutation in the β-sheet of the (β/α)₈-barrel domain changed the conformation of the β-subunit by causing a clash with the E288 side chain. In summary, H235Y is the first mutation in the β-sheet of the (β/α)₈-barrel domain of the β-subunit that abolishes α-β and β-β dimer formation; the presented patient is the second patient to exhibit the motor neuron disease phenotype with P417L and a non-functional allele of HEXB.