Clinical outcome assessments of disease burden and progression in late-onset GM2 gangliosidoses.

The late-onset GM2 gangliosidoses, comprising late-onset Tay-Sachs and Sandhoff diseases, are rare, slowly progressive, neurogenetic disorders primarily characterized by neurogenic weakness, ataxia, and dysarthria. The aim of this longitudinal study was to characterize the natural history of late-onset GM2 gangliosidoses using a number of clinical outcome assessments to measure different aspects of disease burden and progression over time, including neurological, functional, and quality of life, to inform the design of future clinical interventional trials. Patients attending the United States National Tay-Sachs & Allied Diseases Family Conference between 2015 and 2019 underwent annual clinical outcome assessments. Currently, there are no clinical outcome assessments validated to assess late-onset GM2 gangliosidoses; therefore, instruments used or designed for diseases with similar features, or to address various aspects of the clinical presentations, were used. Clinical outcome assessments included the Friedreich's Ataxia Rating Scale, the 9-Hole Peg Test, and the Assessment of Intelligibility of Dysarthric Speech. Twenty-three patients participated in at least one meeting visit (late-onset Tay-Sachs, n = 19; late-onset Sandhoff, n = 4). Patients had high disease burden at baseline, and scores for the different clinical outcome assessments were generally lower than would be expected for the general population. Longitudinal analyses showed slow, but statistically significant, neurological progression as evidenced by worsening scores on the 9-Hole Peg Test (2.68%/year, 95% CI: 0.13-5.29; p = 0.04) and the Friedreich's Ataxia Rating Scale neurological examination (1.31 points/year, 95% CI: 0.26-2.35; p = 0.02). Time since diagnosis to study entry correlated with worsening scores on the 9-Hole Peg Test (r = 0.728; p < 0.001), Friedreich's Ataxia Rating Scale neurological examination (r = 0.727; p < 0.001), and Assessment of Intelligibility of Dysarthric Speech intelligibility (r = -0.654; p = 0.001). In summary, patients with late-onset GM2 gangliosidoses had high disease burden and slow disease progression. Several clinical outcome assessments suitable for clinical trials showed only small changes and standardized effect sizes (change/standard deviation of change) over 4 years. These longitudinal natural history study results illustrate the challenge of identifying responsive endpoints for clinical trials in rare, slowly progressive, neurogenerative disorders where arguably the treatment goal is to halt or decrease the rate of decline rather than improve clinical status. Furthermore, powering such a study would require a large sample size and/or a long study duration, neither of which is an attractive option for an ultra-rare disease with no available treatment. These findings support the development of potentially more sensitive late-onset GM2 gangliosidoses-specific rating instruments and/or surrogate endpoints for use in future clinical trials.

Tandem mass spectrometric enzyme assay for simultaneous detection of Tay-Sachs and Sandhoff diseases in dried blood spots for newborn screening.

GM2 gangliosidosis is a group of rare lysosomal storage disorders (LSDs) including Tay-Sachs disease (TSD) and Sandhoff disease (SD), caused by deficiency in activity of either ß-hexosaminidase A (HexA) or both ß-hexosaminidase A and ß-hexosaminidase B (HexB). Methods for screening and diagnosis of TSD and SD include measurement and comparison of the activity of these two enzymes. Here we report a novel method for duplex screening of dried blood spots (DBS) for TSD and SD by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The method requires incubation of a single 3 mm DBS punch with the assay cocktail followed by the injection into the LC-MS/MS. The performance of the method was evaluated by comparing the confirmed TSD and SD patient DBS to random healthy newborn DBS which showed easy discrimination between the three cohorts. The method is multiplexable with other LSD MS/MS enzyme assays which is critical to the continued expansion of the NBS panels.

Plasma GM2 ganglioside potential biomarker for diagnosis, prognosis and disease monitoring of GM2-Gangliosidosis.

GM2-Gangliosidosis are a group of inherited lysosomal storage pathologies characterized by a large accumulation of GM2 ganglioside in the lysosome. They are caused by mutation in HEXA or HEXB causing reduced or absent activity of a lysosomal ß-hexosaminidase A, or mutation in GM2A causing defect in GM2 activator protein (GM2AP), an essential protein for the activity of the enzyme. Biochemical diagnosis relies on the measurement of ß-hexosaminidases A and B activities, which is able to detect lysosomal enzyme deficiency but fails to identify defects in GM2AP. We developed a rapid, specific and sensitive liquid chromatography-mass spectrometry-based method to measure simultaneously GM1, GM2, GM3 and GD3 molecular species. Gangliosides were analysed in plasma from 19 patients with GM2-Gangliosidosis: Tay-Sachs (n = 9), Sandhoff (n = 9) and AB variant of GM2-Gangliosidosis (n = 1) and compared to 20 age-matched controls. Among patients, 12 have a late adult-juvenile-onset and 7 have an infantile early-onset of the disease. Plasma GM2 molecular species were increased in all GM2-Gangliosidosis patients (19/19), including the patient with GM2A mutation, compared to control individuals and compared to patients with different other lysosomal storage diseases. GM234:1 and GM234:1/GM334:1 ratio discriminated patients from controls with 100% sensitivity and specificity. GM234:1 and GM234:1/GM334:1 were higher in patients with early-onset compared to those with late-onset of the disease, suggesting a relationship with severity. Longitudinal analysis in one adult with Tay-Sachs disease over 9 years showed a positive correlation of GM234:1 and GM234:1/GM334:1 ratio with age at sampling. We propose that plasma GM2 34:1 and its ratio to GM3 34:1 could be sensitive and specific biochemical diagnostic biomarkers for GM2-Gangliosidosis including AB variant and could be useful as a first line diagnostic test and potential biomarkers for monitoring upcoming therapeutic efficacy.

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.

Infantile onset Sandhoff disease: clinical manifestation and a novel common mutation in Thai patients.

BACKGROUND: Sandhoff disease (SD) is an autosomal recessive lysosomal storage disorder, resulting in accumulation of GM2 ganglioside, particular in neuronal cells. The disorder is caused by deficiency of ß-hexosaminidase B (HEX-B), due to pathogenic variant of human HEXB gene. METHOD: This study describes clinical features, biochemical, and genetic defects among Thai patients with infantile SD during 2008-2019. RESULTS: Five unrelated Thai patients presenting with developmental regression, axial hypotonia, seizures, exaggerated startle response to noise, and macular cherry red spot were confirmed to have infantile SD based on deficient HEX enzyme activities and biallelic variants of the HEXB gene. In addition, an uncommon presenting feature, cardiac defect, was observed in one patient. All the patients died in their early childhood. Plasma total HEX and HEX-B activities were severely deficient. Sequencing analysis of HEXB gene identified two variants including c.1652G>A (p.Cys551Tyr) and a novel variant of c.761T>C (p.Leu254Ser), in 90 and 10% of the mutant alleles found, respectively. The results from in silico analysis using multiple bioinformatics tools were in agreement that the p.Cys551Tyr and the p.Leu254Ser are likely pathogenic variants. Molecular modelling suggested that the Cys551Tyr disrupt disulfide bond, leading to protein destabilization while the Leu254Ser resulted in change of secondary structure from helix to coil and disturbing conformation of the active site of the enzyme. Genome-wide SNP array analysis showed no significant relatedness between the five affected individuals. These two variants were not present in control individuals. The prevalence of infantile SD in Thai population is estimated 1 in 1,458,521 and carrier frequency at 1 in 604. CONCLUSION: The study suggests that SD likely represents the most common subtype of rare infantile GM2 gangliosidosis identified among Thai patients. We firstly described a potential common variant in HEXB in Thai patients with infantile onset SD. The data can aid a rapid molecular confirmation of infantile SD starting with the hotspot variant and the use of expanded carrier testing.

Atypical presentation of late-onset Sandhoff disease: a case report.

BACKGROUND AND PURPOSE: Sandhoff disease is a rare type of hereditary (autosomal recessive) GM2-gangliosidosis, which is caused by mutation of the HEXB gene. Disruption of the ß subunit of the hexosaminidase (Hex) enzyme affects the function of both the Hex-A and Hex-B isoforms. The severity and the age of onset of the disease (infantile or classic; juvenile; adult) depends on the residual activity of the enzyme. The late-onset form is characterized by diverse symptomatology, comprising motor neuron disease, ataxia, tremor, dystonia, psychiatric symptoms and neuropathy. METHODS: A 36-year-old female patient has been presenting progressive, symmetrical lower limb weakness for 9 years. Detailed neurological examination revealed mild symmetrical weakness in the hip flexors without the involvement of other muscle groups. The patellar reflex was decreased on both sides. Laboratory tests showed no relevant alteration and routine electroencephalography and brain MRI were normal. Nerve conduction studies and electromyography revealed alterations corresponding to sensory neuropathy. Muscle biopsy demonstrated signs of mild neurogenic lesion. Her younger brother (32-year-old) was observed with similar symptoms. RESULTS: Detailed genetic study detected a known pathogenic missense mutation and a 15,088 base pair long known pathogenic deletion in the HEXB gene (NM_000521.4:c.1417G>A; NM_000521:c.-376-5836_669+1473del; double heterozygous state). Segregation analysis and hexosaminidase enzyme assay of the family further confirmed the diagnosis of late-onset Sandhoff disease. CONCLUSION: The purpose of this case report is to draw attention to the significance of late-onset Sandhoff disease amongst disorders presenting with proximal predominant symmetric lower limb muscle weakness in adulthood.

Substrate Reduction Therapy for Sandhoff Disease through Inhibition of Glucosylceramide Synthase Activity.

Neuronopathic glycosphingolipidoses are a sub-group of lysosomal storage disorders for which there are presently no effective therapies. Here, we evaluated the potential of substrate reduction therapy (SRT) using an inhibitor of glucosylceramide synthase (GCS) to decrease the synthesis of glucosylceramide (GL1) and related glycosphingolipids. The substrates that accumulate in Sandhoff disease (e.g., ganglioside GM2 and its nonacylated derivative, lyso-GM2) are distal to the drug target, GCS. Treatment of Sandhoff mice with a GCS inhibitor that has demonstrated CNS access (Genz-682452) reduced the accumulation of GL1 and GM2, as well as a variety of disease-associated substrates in the liver and brain. Concomitant with these effects was a significant decrease in the expression of CD68 and glycoprotein non-metastatic melanoma B protein (Gpnmb) in the brain, indicating a reduction in microgliosis in the treated mice. Moreover, using in vivo imaging, we showed that the monocytic biomarker translocator protein (TSPO), which was elevated in Sandhoff mice, was normalized following Genz-682452 treatment. These positive effects translated in turn into a delay (∼28 days) in loss of motor function and coordination, as measured by rotarod latency, and a significant increase in longevity (∼17.5%). Together, these results support the development of SRT for the treatment of gangliosidoses, particularly in patients with residual enzyme activity.

THE LYSOSOMAL STORAGE DISEASE GM2 GANGLIOSIDOSIS IN CAPTIVE BANDED MONGOOSE SIBLINGS ( MUNGOS MUNGO).

This study reports the occurrence of the lysosomal storage disease GM2 gangliosidosis (Sandhoff disease) in two 11-mo-old captive-bred, male and female mongoose siblings ( Mungos mungo). The clinical signs and the pathological findings reported here were similar to those reported in other mammalian species. Light microscopy revealed an accumulation of stored material in neurons and macrophages accompanied by a significant neuronal degeneration (swelling of neuronal soma, loss of Nissl substance, and neuronal loss) and gliosis. Electron microscopy of brain tissue identified the stored material as membrane-bound multilamellar bodies. An almost complete lack of total hexosaminidase activity in serum suggested a defect in the HEXB gene (Sandhoff disease in humans). High-performance thin-layer chromatography and mass spectrometry confirmed the accumulation of GM2 ganglioside in brain and kidney tissue, and the lectin staining pattern of the brain tissue further corroborated the diagnosis of a Sandhoff-type lysosomal storage disease.

Clinical, biochemical and mutation profile in Indian patients with Sandhoff disease.

Sandhoff disease (SD) is an autosomal recessive neurodegenerative lysosomal storage disorder caused by mutations in HEXB gene. Molecular pathology is unknown in Indian patients with SD. The present study is aimed to determine mutations spectrum and molecular pathology leading to SD in 22 unrelated patients confirmed by the deficiency of ß-hexosaminidase-A and total-hexosaminidase in leukocytes. To date, nearly 86 mutations of HEXB have been described, including five large deletions. Over all we have identified 13 mutations in 19 patients, eight of which were novel, including two missense mutations [c.611G>A (p.G204E), c. 634A>T (p.H212Y)], two nonsense mutations [c.333G>A (p.W111X), c.298C>T (p.R100X)], one splice site mutation c.1082+5 G>T, two small in-frame deletions [c.534_541delAGTTTATC (p.V179RfsX10), c.1563_1573delTATGGATGACG (p.M522LfsX2)] and one insertion c.1553_1554insAAGA (p.D518EfsX8). We have also identified previously known, five sequence variations leading to amino acid changes [c.926G>A (p.C309Y), c.1597C>T (p.R533C)], one nonsense mutation c.850 C>T (p.R284X), one splice site mutation c.1417+1 G-A and one insertion c.1591_1592insC (p.R531TfsX22). Mutation was not identified in three patients. We observed from this study that mutation c.850C>T (p.R284X) was identified in 4/19 (21%) patients which is likely to be the most common mutation in the country. This is the first study providing insight into the molecular basis of SD in India.

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 ß-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.

Biomarkers of central nervous system inflammation in infantile and juvenile gangliosidoses.

BACKGROUND: The gangliosidoses (Tay-Sachs disease, Sandhoff disease, and GM1-gangliosidosis) are progressive neurodegenerative diseases caused by lysosomal enzyme activity deficiencies and consequent accumulation of gangliosides in the central nervous system (CNS). The infantile forms are distinguished from the juvenile forms by age of onset, rate of disease progression, and age of death. There are no approved treatments for the gangliosidoses. In search of potential biomarkers of disease, we quantified 188 analytes in CSF and serum from living human patients with longitudinal (serial) measurements. Notably, several associated with inflammation were elevated in the CSF of infantile gangliosidosis patients, and less so in more slowly progressing forms of juvenile gangliosidosis, but not in MPS disease. Thirteen CSF and two serum biomarker candidates were identified. Five candidate biomarkers were distinguished by persistent elevation in the CSF of patients with the severe infantile phenotype: ENA-78, MCP-1, MIP-1α, MIP-1ß, and TNFR2. Correspondence of abnormal elevation with other variables of disease-i.e., severity of clinical phenotype, differentiation from changes in serum, and lack of abnormality in other neurodegenerative lysosomal diseases-identifies these analytes as biomarkers of neuropathology specific to the gangliosidosis diseases.

Incidence and carrier frequency of Sandhoff disease in Saskatchewan determined using a novel substrate with detection by tandem mass spectrometry and molecular genetic analysis.

Sandhoff disease is a rare progressive neurodegenerative genetic disorder with a high incidence among certain isolated communities and ethnic groups around the world. Previous reports have shown a high occurrence of Sandhoff disease in northern Saskatchewan. Newborn screening cards from northern Saskatchewan were retrospectively screened in order to investigate the incidence and determine the carrier frequency of Sandhoff disease in these communities. PCR-based screening was conducted for the c.115delG (p.(Val39fs)) variant in the HEXB gene that was previously found in 4 Sandhoff disease patients from this area. The carrier frequency for this allele was estimated to be ~1:27. MS/MS-based screening of hexosaminidase activity along with genetic sequencing allowed for the identification of additional variants based on low total hexosaminidase activity and high % hexosaminidase A activity relative to c.115delG carriers. In total 4 pathogenic variants were discovered in the population (c.115delG, c.619A>G, c.1601G>T, and c.1652G>A) of which two are previously unreported (c.1601G>T and c.1652G>A). The combined carrier frequency of these alleles in the study area was estimated at ~1:15. Based on the number of cases of Sandhoff disease from this area we estimate the incidence to be ~1:390 corresponding to a child being born with the disease every 1-2 years on average. The results from our study were then compared with variants in the HEXB gene from the genomes available from the 1000 Genomes project. A total of 19 HEXB variants were found in the 1092 genomes of which 5 are suspected of having a deleterious effect on hexosaminidase activity. The estimated carrier frequency of Sandhoff disease in Saskatchewan at 1:15 is more than 3 times higher than the carrier frequency in the global sample provided by the 1000 Genomes project at 1:57.

Integrated multiplex ligation dependent probe amplification (MLPA) assays for the detection of alterations in the HEXB, GM2A and SMARCAL1 genes to support the diagnosis of Morbus Sandhoff, M. Tay-Sachs variant AB and Schimke immuno-osseous dysplasia in humans.

Multiplex ligation dependent probe amplification (MLPA) assays were designed for the genes HEXB (OMIM: 606873), GM2A (OMIM: 613109) and SMARCAL1 (OMIM: 606622) of humans. Two sets of synthetic MLPA probes for these coding exons were tested. Changes in copy numbers were detected as well as single nucleotide polymorphisms (SNPs) by complementary DNA sequence analyses. The MLPA method was shown to be reliable for mutation detection and identified five published and 12 new mutations. In all cases from a Morbus Sandhoff cohort of patients, exclusively one variation in copy number was observed and linked to a nucleotide alteration called c.1614-14C>A. This deletion comprised exons 1-5. One of these cases is described in detail. Deletions were neither detected in the GM2A nor the SMARCAL1 genes. The MLPA assays complement routine diagnostics for M. Sandhoff (OMIM: 268800), M. Tay-Sachs variant AB (OMIM: 272750) and Schimke immuno-osseous dysplasia (OMIM: 242900).

[HEXB gene study and prenatal diagnosis for a family affected by infantile Sandhoff disease].

OBJECTIVE: To investigate the phenotype and genotype of a Chinese boy and his family affected by infantile Sandhoff disease. METHODS: The proband, a boy, was the first child born to a non-consanguineous couple. He showed startle reaction after birth and progressive psychomotor regression from the age of 8 months. From the age of 16 months, he presented seizures. When he was admitted at 17 months old, severe mental retardation and weakness were observed. Fundus examination revealed bilateral cherry-red spots in the macula and optic atrophy. Cranial MRI revealed abnormal signals in the thalamus, basal ganglia and white matter. Enzymatic assay and genetic testing were performed for the diagnosis. His mother visited us at 18 weeks of pregnancy seeking for prenatal diagnosis. HEXB gene diagnosis to the fetus was performed by direct sequencing. RESULTS: Significant deficient total ß-hexosaminidase (A and B) activity in peripheral leucocytes of the patient (0.0 nmol/h/mg compared with normal control, 41.9 to 135.1 nmol/h/mg) supported the diagnosis of Sandhoff disease. On his HEXB gene, two mutations were found. c.1645G-A (p.G549R) was novel. c.IVS7-48T was a reported mutation. Now, the patient was 2 years and 3 months old, with progressive general failure, severe epilepsy, blindness and hypermyotonia. Subsequently, the mother visited us at 18 weeks of pregnancy seeking for prenatal diagnosis. HEXB gene analysis of the amniocytes was performed by direct sequencing. Both of the two mutations were not detected from cultured amniocytes. The result revealed that the fetus was not affected by Sandhoff disease. A healthy girl, the sibling of the proband, was born in term. Postnatal enzyme analysis and genetic analysis of the cord blood cells confirmed the prenatal diagnosis. CONCLUSION: One novel mutation on HEXB gene was identified. Prenatal diagnosis to the fetus of this family was performed by amniocytes gene analysis.

A case of Sandhoff disease caused by a novel ß-hexosaminidase B (HEXB) mutation c.118delG (p.A40fs*24): A case report from China.

BACKGROUND: Sandhoff disease (SD, Online Mendelian Inheritance in Man: 268800) is an autosomal recessive lysosomal storage disorder caused by variants of the ß-hexosaminidase B (HEXB) gene (Online Mendelian Inheritance in Man: 606873). The HEXB gene has been mapped to chromosome 5q13 and contains 14 exons. The symptoms of SD include progressive weakness, intellectual disability, visual and hearing impairment, exaggerated startle response, and seizures; the patients usually die before the age of 3 years.[1]. CASE SUMMARY: We present a case of SD caused by a homozygous frameshift mutation in the HEXB gene, c.118delG (p.A40fs*24). The male child, aged 2 years 7 months, showed movement retrogression with orbital hypertelorism at age 2 years, accompanied by seizures. Magnetic resonance imaging of the head showed cerebral atrophy and delayed myelination of the white matter of the brain. CONCLUSION: A novel homozygous frameshift c.118delG (p.A40fs*24) variant of HEXB has caused SD in the child. The major symptoms are intellectual disability, visual and hearing impairment, and seizures. Investigation will be continued in the future to comprehensively describe the genotype/phenotype and gain information on other associated features to understand the variable expressivity of this condition.

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 ß-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.

Infantile Sandhoff disease with ventricular septal defect: a case report.

BACKGROUND: Infantile Sandhoff disease is a rare inherited disorder that progressively destroys nerve cells in the brain and spinal cord, and is classified under lysosomal storage disorder. It is an autosomal recessive disorder of sphingolipid metabolism that results from deficiency of the lysosomal enzymes ß-hexosaminidase A and B. The resultant accumulation of GM2 ganglioside within both gray matter nuclei and myelin sheaths of the white matter results in eventual severe neuronal dysfunction and neurodegeneration. CASE PRESENTATION: We evaluated a 3.5-year-old Comorian girl from the United Arab Emirates who presented with repeated chest infections with heart failure due to ventricular septal defect, neuroregression, recurrent seizures, and cherry-red spots over macula. She had macrocephaly, axial hypotonia, hyperacusis, and gastroesophageal reflux. Organomegaly was absent. Brain magnetic resonance imaging, metabolic tests, and genetic mutations confirmed the diagnosis. Despite multidisciplinary therapy, the girl succumbed to her illness. CONCLUSION: Though early cardiac involvement can be seen with novel mutations, it is extremely rare to find association of ventricular septal defect in infantile Sandhoff disease. Neuroregression typically starts around 6 months of age. We report this case because of the unusual association of a congenital heart disease with underlying infantile Sandhoff disease and symptomatic heart failure in the first month of life with eventual fatal outcome.

A case of adult onset Sandhoff disease that mimics Brown-Vialetto-Van Laere syndrome.

Sandhoff disease is a rare fatal infantile neurologic disorder. Adult onset Sandhoff is even rarer. Variability of clinical features in adult onset Sandhoff patients and overlaps between these and features of other neurologic diseases have sometimes led to mis-diagnosis. We describe an adult onset Sandhoff disease affected individual whose clinical presentation were also consistent with the Brown-Vialetto-Van Laere syndrome (BVVL) diagnosis. Screening of BVVL-causing genes, SLC52A3 and SLC52A2, did not identify candidate disease-causing mutations, but exome sequencing revealed compound heterozygous mutations in the known Sandhoff disease-causing gene, HEXB. Decreased blood hexosaminidase activity and evidence of cerebellar atrophy confirmed Sandhoff disease diagnosis. To the best of our knowledge, this is the first report of a Sandhoff disease case that mimics BVVL and that presents with prominent cranial nerve involvement. For differential diagnosis, measurement of hexosaminidase activity and MRI should quickly be performed. Genetic analysis can be done for confirmation of diagnosis.