Challenging Diagnosis of a Patient with Two Novel Variants in the SYNE1 Gene.

We report a case of SYNE1-associated autosomal recessive spinocerebellar ataxia (SCAR8) presenting with a complex multisystemic phenotype, including highly elevated creatine kinase levels and lower-leg muscle atrophy. In addition to identifying two novel pathogenic variants in the SYNE1 gene, whole-exome sequencing revealed three variants of uncertain significance in the DYSF gene. Electromyography and muscle magnetic resonance imaging indicated a neurogenic pattern of muscle involvement. These findings, along with the segregation analysis of the variants, allowed us to exclude DYSF-associated muscular dystrophy; however, we cannot entirely rule out the possibility that the DYSF gene variants may act as modifiers of the patient's phenotype.

Clinical and genetic variability among Bulgarian patients with autosomal recessive spastic ataxia of Charlevoix-Saguenay.

BACKGROUND: Autosomal recessive spastic ataxia ofCharlevoix-Saguenay (ARSACS) is a rare neurodegenerative disorder characterizedby early-onset cerebellar ataxia, peripheral sensorimotor neuropathy, and lowerlimb spasticity. We present clinical andgenetic data of the first Bulgarian patients diagnosed with ARSACS by wholeexome sequencing (WES). METHODS: Variant filtering was performed usinglocally established pipeline and the selected variants were analysed by Sangersequencing. All patients underwent clinical examination and testingincluding the standard rating scales for spastic paraplegia and ataxia. RESULTS: Five different SACS gene variants, three of which novel, have been identified inpatients from three different ethnic groups. In addition to the classicalclinical triad, brain MRI revealed cerebellar atrophy, linear pontineT2-hypointensities, and hyperintense rim lateral tothalamus combined with retinal nerve fiber layer thickening on opticcoherence tomography (OCT). CONCLUSION: We expand the mutation, geographic, and phenotypic spectrum of ARSACS, adding Bulgaria to the world map of the disease, and drawing attention to the fact that it is still misdiagnosed. We demonstrated that brain MRI and OCT are necessary clinical tests for ARSACS diagnosis, even if one of the cardinal clinical features is lacking.

Ataxias in Brazil: 17 years of experience in an ataxia center.

BACKGROUND: Cerebellar ataxias comprise sporadic and genetic etiologies. Ataxia may also be a presenting feature in hereditary spastic paraplegias (HSPs). OBJECTIVE: To report a descriptive analysis of the frequency of different forms of cerebellar ataxia evaluated over 17 years in the Ataxia Unit of Universidade Federal de São Paulo, Brazil. METHODS: Charts of patients who were being followed from January 2007 to December 2023 were reviewed. We used descriptive statistics to present our results as frequencies and percentages of the overall analysis. Diagnosed patients were classified according to the following 9 groups: sporadic ataxia, spinocerebellar ataxias (SCAs), other autosomal dominant cerebellar ataxias, autosomal recessive cerebellar ataxias (ARCAs), mitochondrial ataxias, congenital ataxias, X-linked ataxias, HSPs, and others. RESULTS: There were 1,332 patients with ataxias or spastic paraplegias. Overall, 744 (55.85%) of all cases were successfully diagnosed: 101 sporadic ataxia, 326 SCAs, 20 of other autosomal dominant cerebellar ataxias, 186 ARCAs, 6 X-linked ataxias, 2 mitochondrial ataxias, 4 congenital ataxias, and 51 HSPs. CONCLUSION: This study describes the frequency of cerebellar ataxias in a large group of patients followed for the past 17 years, of whom 55% obtained a definitive clinical or molecular diagnosis. Future demographic surveys in Brazil or Latin American remain necessary.

ANTECEDENTES: Ataxias cerebelares compreendem as etiologias esporádicas e genéticas. Ataxia também pode ser uma característica das paraplegias espásticas hereditárias (HSPs). OBJETIVO: Relatar uma análise descritiva da frequência das diferentes formas de ataxias cerebelares avaliadas ao longo de 17 anos no Setor da Ataxias da Universidade Federal de São Paulo, Brasil. MéTODOS: Prontuários de pacientes acompanhados de janeiro de 2007 a dezembro de 2023 foram revisados. Usamos análise descritiva para apresentar nossos resultados como frequências e percentuais. Os pacientes foram classificados de acordo com os 9 grupos seguintes: ataxias esporádicas, ataxias espinocerebelares (SCA), outras ataxias cerebelares autossômicas dominantes, ataxias cerebelares autossômicas recessivas (ARCA), ataxias mitocondriais, ataxias congênitas, ataxias ligadas ao X, PEH e outros. RESULTADOS: Foram avaliados 1.332 pacientes. Desse total, 744 tiveram um diagnóstico definitivo: 101 ataxias esporádicas, 326 SCA, 20 outras ataxias cerebelares autossômicas dominantes, 186 (ARCA), 6 ataxias ligadas ao X, 2 ataxias mitocondriais, 4 ataxias congênitas e 51 HSP. CONCLUSãO: Esse estudo descreve a frequência e a etiologia das ataxias em um grande grupo de pacientes acompanhados nos últimos 17 anos, dos quais 55% obtiveram diagnóstico clínico ou molecular definitivos. Estudos demográficos futuros do Brasil ou da América Latina continuam sendo necessários.

MRI-ARSACS: An Imaging Index for Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) Identification Based on the Multicenter PROSPAX Study.

BACKGROUND: Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) and hereditary spastic paraplegia type 7 (SPG7) represent the most common genotypes of spastic ataxia (SPAX). To date, their magnetic resonance imaging (MRI) features have only been described qualitatively, and a pure neuroradiological differential diagnosis between these two conditions is difficult to achieve. OBJECTIVES: To test the performance of MRI measures to discriminate between ARSACS and SPG7 (as an index of common SPAX disease). METHODS: In this prospective multicenter study, 3D-T1-weighted images of 59 ARSACS (35.4 ± 10.3 years, M/F = 33/26) and 78 SPG7 (54.8 ± 10.3 years, M/F = 51/27) patients of the PROSPAX Consortium were analyzed, together with 30 controls (45.9 ± 16.9 years, M/F = 15/15). Different linear and surface measures were evaluated. A receiver operating characteristic analysis was performed, calculating area under the curve (AUC) and corresponding diagnostic accuracy parameters. RESULTS: The pons area proved to be the only metric increased exclusively in ARSACS patients (P = 0.02). Other different measures were reduced in ARSACS and SPG7 compared with controls (all with P ≤ 0.005). A cut-off value equal to 1.67 of the pons-to-superior vermis area ratio proved to have the highest AUC (0.98, diagnostic accuracy 93%, sensitivity 97%) in discriminating between ARSACS and SPG7. CONCLUSIONS: Evaluation of the pons-to-superior vermis area ratio can discriminate ARSACS from other SPAX patients, as exemplified here by SPG7. Hence, we hereby propose this ratio as the Magnetic Resonance Index for the Assessment and Recognition of patients harboring SACS mutations (MRI-ARSACS), a novel diagnostic tool able to identify ARSACS patients and useful for discriminating ARSACS from other SPAX patients undergoing MRI. © 2024 International Parkinson and Movement Disorder Society.

SCAR32: Functional characterization and expansion of the clinical-genetic spectrum.

OBJECTIVE: Biallelic mutations in PRDX3 have been linked to autosomal recessive spinocerebellar ataxia type 32. In this study, which aims to contribute to the growing body of knowledge on this rare disease, we identified two unrelated patients with mutations in PRDX3. We explored the impact of PRDX3 mutation in patient skin fibroblasts and the role of the gene in neurodevelopment. METHODS: We performed trio exome sequencing that identified mutations in PRDX3 in two unrelated patients. We also performed functional studies in patient skin fibroblasts and generated a "crispant" zebrafish (Danio rerio) model to investigate the role of the gene during nervous system development. RESULTS: Our study reports two additional patients. Patient 1 is a 19-year-old male who showed a novel homozygous c.525_535delGTTAGAAGGTT (p. Leu176TrpfsTer11) mutation as the genetic cause of cerebellar ataxia. Patient 2 is a 20-year-old male who was found to present the known c.425C>G/p. Ala142Gly variant in compound heterozygosity with the p. Leu176TrpfsTer11 one. While the fibroblast model failed to recapitulate the pathological features associated with PRDX3 loss of function, our functional characterization of the prdx3 zebrafish model revealed motor defects, increased susceptibility to reactive oxygen species-triggered apoptosis, and an impaired oxygen consumption rate. CONCLUSIONS: We identified a new variant, thereby expanding the genetic spectrum of PRDX3-related disease. We developed a novel zebrafish model to investigate the consequences of prdx3 depletion on neurodevelopment and thus offered a potential new tool for identifying new treatment opportunities.

New Case of Spinocerebellar Ataxia, Autosomal Recessive 4, Due to VPS13D Variants.

Movement disorders such as bradykinesia, tremor, dystonia, chorea, and myoclonus most often arise in several neurodegenerative diseases with basal ganglia and white matter involvement. While the pathophysiology of these disorders remains incompletely understood, dysfunction of the basal ganglia and related brain regions is often implicated. The VPS13D gene, part of the VPS13 family, has emerged as a crucial player in neurological pathology, implicated in diverse phenotypes ranging from movement disorders to Leigh syndrome. We present a clinical case of VPS13D-associated disease with two variants in the VPS13D gene in an adult female. This case contributes to our evolving understanding of VPS13D-related diseases and underscores the importance of genetic screening in diagnosing and managing such conditions.

Prediction of Individual Disease Progression Including Parameter Uncertainty in Rare Neurodegenerative Diseases: The Example of Autosomal-Recessive Spastic Ataxia Charlevoix Saguenay (ARSACS).

The aim of this study was to develop a model to predict individual subject disease trajectories including parameter uncertainty and accounting for missing data in rare neurological diseases, showcased by the ultra-rare disease Autosomal-Recessive Spastic Ataxia Charlevoix Saguenay (ARSACS). We modelled the change in SARA (Scale for Assessment and Rating of Ataxia) score versus Time Since Onset of symptoms using non-linear mixed effect models for a population of 173 patients with ARSACS included in the prospective real-world multicenter Autosomal Recessive Cerebellar Ataxia (ARCA) registry. We used the Multivariate Imputation Chained Equation (MICE) algorithm to impute missing covariates, and a covariate selection procedure with a pooled p-value to account for the multiply imputed data sets. We then investigated the impact of covariates and population parameter uncertainty on the prediction of the individual trajectories up to 5 years after their last visit. A four-parameter logistic function was selected. Men were estimated to have a 25% lower SARA score at disease onset and a moderately higher maximum SARA score, and time to progression (T50) was estimated to be 35% lower in patients with age of onset over 15 years. The population disease progression rate started slowly at 0.1 points per year peaking to a maximum of 0.8 points per year (at 36.8 years since onset of symptoms). The prediction intervals for SARA scores 5 years after the last visit were large (median 7.4 points, Q1-Q3: 6.4-8.5); their size was mostly driven by individual parameter uncertainty and individual disease progression rate at that time.

A 24-Year-Old Man With Spastic Ataxia and Hypodontia.

A 24-year-old man presented with progressive gait instability, marked spinal cord atrophy, and dental radiography showing the absence of several elements, microdontia, and taurodontia. What is your diagnosis?

Neuropathy in ARSACS is demyelinating but without typical nerve enlargement in nerve ultrasound.

BACKGROUND: To specify peripheral nerve affection in autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) by correlating high-resolution nerve ultrasound and nerve conduction studies. METHODS: We assessed a cohort of 11 ARSACS patients with standardized nerve conduction studies and high-resolution ultrasound of peripheral nerves and compared nerve ultrasound findings to a healthy control group matched for age, sex, size and weight. RESULTS: Mean age of patients was 39.0 (± 14.1) years and disease duration at assessment 30.6 (± 12.5) years. All patients presented with a spasticity, ataxia and peripheral neuropathy. Neuropathy appeared to be primarily demyelinating in 9/11 cases and was not classifiable in 2/11 cases due to not evocable potentials. Nerve ultrasound revealed a normal ultrasound pattern sum score (UPSS) in each ARSACS patient and no significant nerve enlargement compared to the control group. CONCLUSIONS: Peripheral neuropathy in ARSACS showed primarily demyelinating rather than axonal characteristics and presented without nerve enlargement. As demyelinating neuropathies do commonly present enlarged nerves we recommend further genetic testing of the SACS gene in patients who present with this combination of demyelinating neuropathy without nerve enlargement. ARSACS cases that initially presented only with neuropathy without spasticity or ataxia and therefore were misdiagnosed as Charcot-Marie-Tooth disease are supporting this suggestion.

Potential Benefit of Channel Activators in Loss-of-Function Primary Potassium Channelopathies Causing Heredoataxia.

Potassium channels (KCN) are transmembrane complexes that regulate the resting membrane potential and the duration of action potentials in cells. The opening of KCN brings about an efflux of K+ ions that induces cell repolarization after depolarization, returns the transmembrane potential to its resting state, and enables for continuous spiking ability. The aim of this work was to assess the role of KCN dysfunction in the pathogenesis of hereditary ataxias and the mechanisms of action of KCN opening agents (KCO). In consequence, a review of the ad hoc medical literature was performed. Among hereditary KCN diseases causing ataxia, mutated Kv3.3, Kv4.3, and Kv1.1 channels provoke spinocerebellar ataxia (SCA) type 13, SCA19/22, and episodic ataxia type 1 (EA1), respectively. The K+ efflux was found to be reduced in experimental models of these diseases, resulting in abnormally prolonged depolarization and incomplete repolarization, thereby interfering with repetitive discharges in the cells. Hence, substances able to promote normal spiking activity in the cerebellum could provide symptomatic benefit. Although drugs used in clinical practice do not activate Kv3.3 or Kv4.3 directly, available KCO probably could ameliorate ataxic symptoms in SCA13 and SCA19/22, as verified with acetazolamide in EA1, and retigabine in a mouse model of hypokalemic periodic paralysis. To summarize, ataxia could possibly be improved by non-specific KCO in SCA13 and SCA19/22. The identification of new specific KCO agents will undoubtedly constitute a promising therapeutic strategy for these diseases.

Widening the clinical, radiological and genetic spectrum of autosomal recessive ataxia of Charlevoix-Saguenay in Indian patients.

BACKGROUND: Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), classically presenting as a triad of early-onset cerebellar ataxia, lower extremity spasticity and peripheral neuropathy, is caused by mutations in SACS gene which encodes the protein sacsin. OBJECTIVE: To provide new insight into the occurrence of SACS mutations in South India. METHODS: Patients with three cardinal features of ARSACS-peripheral neuropathy, cerebellar ataxia, and pyramidal tract signs were included. Nine patients were clinically identified and genetically evaluated. Mutation screening of SACS by targeted sequencing of 40 recessive ataxia genes panel by next-generation sequencing was conducted. Additional investigations included magnetic resonance imaging (MRI), fundoscopy, optical coherence tomography (OCT) and nerve conduction studies (NCS). Functional disability was assessed by the Spinocerebellar Degeneration Functional Score. RESULTS: Two hundred and fifteen cerebellar ataxia patients were screened, and 9 patients with cerebellar ataxia with spasticity, peripheral neuropathy and MRI brain characteristics, consistent with a clinical diagnosis of ARSACS were identified, of which 7 patients were identified to have mutation in the SACS gene and are detailed hereafter. Age of presentation ranged from 20 to 55 years (29.8 ± 11.9) with a mean disease duration of 12.7 years (SD-7.65, range 5-22 years). All except one had onset of symptoms in the form of an ataxic gait noticed before 20 years of age. Additional features were subnormal intelligence (4/7), slow and hypometric saccades (1/7), seizures (1/7), kyphoscoliosis (1/7) and dysmorphic facies (1/7). SDFS was 3 in 5/7 patients signifying moderate disability with independent ambulation. MRI showed cerebellar atrophy with predominant atrophy of the superior vermis (7/7), horizontal linear T2 hypointensities in the pons(7/7), hyperintensities where lateral pons merges with the middle cerebellar peduncle (MCP) (7/7) well seen in fluid-attenuated inversion recovery (FLAIR) images, thickening of MCP (3/7), symmetric lateral thalamic hyperintensities (6/7), posterior fossa arachnoid cyst (4/7),thinning of posterior mid-body of corpus callosum (7/7), marginal mineralisation of the basal ganglia (7/7), bilateral parietal atrophy (7/7) and thinning of corticospinal tract on diffusion tensor imaging (DTI) (7/7). We identified pathogenic homozygous frameshift mutations in the SACS gene in six patients (including two siblings), while one patient had a heterozygous pathogenic deletion. CONCLUSIONS: This is the largest series of genetically confirmed ARSACS patients from India highlighting the clinical, ophthalmological, imaging and genetic features of this cohort.

Toward a Better Understanding of Walking Speed in Ataxia of Charlevoix-Saguenay: a Factor Exploratory Study.

Mobility limitations, including a decrease in walking speed, are major issues for people with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). Improving our understanding of factors influencing walking speed in ARSACS may inform the development of future interventions for gait rehabilitation and contribute to better clinical practices. The objective of the study was to identify the factors influencing the self-selected walking speed in adults with ARSACS. The dependent variable of this cross-sectional study was the self-selected speed and the factors (independent variables) were age, sex, balance, balance confidence, knee flexion and extension cocontraction indexes, lower limb coordination, passive range of motion of ankle dorsiflexion, knee and hip extension, and global spasticity. Multiple regression models were used to assess the relationships between walking speed and each factor individually. Six factors were significantly associated with walking speed and thus included in regression models. The models explained between 42.4 and 66.5% of the total variance of the self-selected walking speed. The factors that most influence self-selected walking speed are balance and lower limb coordination. In order of importance, the other factors that also significantly influence self-selected walking speed are ankle dorsiflexion range of motion, lower limb spasticity, knee extension range of motion, and confidence in balance. Balance and lower limb coordination should be targeted in rehabilitation interventions to maintain walking ability and functional independence as long as possible. The six factors identified should also be included in future studies to deepen our understanding of walking speed.

Documenting manifestations and impacts of autosomal recessive spastic ataxia of Charlevoix-Saguenay to develop patient-reported outcome.

BACKGROUND: Autosomal recessive cerebellar ataxias (ARCA) are a group of rare inherited disorders characterized by degeneration or abnormal development of the cerebellum. Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is one of the most prevalent in Europe. OBJECTIVES: The aim of this study is to provide a better understanding of the manifestations and impacts of ARSACS. METHODS: A systematic review of the literature was conducted, followed by a qualitative study using semistructured interviews and discussion groups to obtain the experience of people affected. RESULTS: According to the PROMIS framework, the results show manifestations and impacts in three components of health: physical, mental, and social. Fatigue and struggles with balance and dexterity are the physical manifestations of the disease most often cited by participants. Negative affects such as frustration and depression are among the mental health impacts with some loss in cognitive abilities. Social health is the least documented component; nonetheless, people with the disease report significant impacts in terms of social relationships, activities and work. CONCLUSIONS: These findings shed new light on the experience of people with recessive ataxia and identify key aspects to assess to improve their overall health.

A Novel Nonsense Variant in GRM1 Causes Autosomal Recessive Spinocerebellar Ataxia 13 in a Consanguineous Pakistani Family.

Background and objectives: Autosomal recessive spinocerebellar ataxia-13 (SCAR13) is an ultra-rare disorder characterized by slowly progressive cerebellar ataxia, cognitive deficiencies, and skeletal and oculomotor abnormalities. The objective of this case report is to expand the clinical and molecular spectrum of SCAR13. Methods: We investigated a consanguineous Pakistani family with four patients partially presenting with clinical features of SCAR13 using whole exome sequencing. Segregation analysis was performed by Sanger sequencing in all the available individuals of the family. Results: Patients presented with quadrupedal gait, delayed developmental milestones, non-progressive peripheral neuropathy, and cognitive impairment. Whole exome sequencing identified a novel pathogenic nonsense homozygous variant, Gly240*, in the gene GRM1 as a cause of SCAR13 that segregates with the recessive disease. Discussion: We report a novel homozygous nonsense variant in the GRM1 gene in four Pakistani patients presenting with clinical features that partially overlap with the already reported phenotype of SCAR13. In addition, the family presented quadrupedal gait and non-progressive symptoms, manifestations which have not been recognized previously. So far, only four variants in GRM1 have been reported, in families of Roma, Iranian, and Tunisian origins. The current study adds to the mutation spectrum of GRM1 and provides a rare presentation of SCAR13, the first from the Pakistani population.

The ARSACS disease protein sacsin controls lysosomal positioning and reformation by regulating microtubule dynamics.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay is a fatal brain disorder featuring cerebellar neurodegeneration leading to spasticity and ataxia. This disease is caused by mutations in the SACS gene that encodes sacsin, a massive 4579-amino acid protein with multiple modular domains. However, molecular details of the function of sacsin are not clear. Here, using live cell imaging and biochemistry, we demonstrate that sacsin binds to microtubules and regulates microtubule dynamics. Loss of sacsin function in various cell types, including knockdown and KO primary neurons and patient fibroblasts, leads to alterations in lysosomal transport, positioning, function, and reformation following autophagy. Each of these phenotypic changes is consistent with altered microtubule dynamics. We further show the effects of sacsin are mediated at least in part through interactions with JIP3, an adapter for microtubule motors. These data reveal a new function for sacsin that explains its previously reported roles and phenotypes.

Cannabis use in patients with Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay.

Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) is an early-onset cerebellar ataxia with often presence of peripheral sensorimotor neuropathy and lower limb spasticity. Recently, the presence of pain has been associated with ARSACS in a quarter of the population in relation to spasms and neuropathic pain. However, limited therapeutic options available to patients and the occurrence of persistent symptoms despite treatment with the usual pharmacologic agents have led to exploring cannabis as a potential alternative. The aim of this study was to characterize the profile of cannabis use among patients with ARSACS. Phone interviews were conducted to document current or former cannabis use. Reasons of cannabis use and the characteristics of use were also investigated. Among the 50 study participants, 18% currently used cannabis, 40% reported at least one occurrence of cannabis use and 42% reported having never used cannabis. A greater proportion of patients with regular cannabis use reported chronic pain in comparison to those who never used. Although less frequent than ataxia, spasticity, muscle cramps or muscle spasms, which were independently reported by more than half of the studied sample, chronic pain was notably present in 30% of participants. While our study did not assess the therapeutic effects of cannabis, our results highlight that there is a potential role for cannabis and cannabinoids in the management of multiple ARSACS-associated symptoms and that agents modulating the endocannabinoid system need to be properly investigated.

Integrative Organelle-Based Functional Proteomics: In Silico Prediction of Impaired Functional Annotations in SACS KO Cell Model.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is an inherited neurodegenerative disease characterized by early-onset spasticity in the lower limbs, axonal-demyelinating sensorimotor peripheral neuropathy, and cerebellar ataxia. Our understanding of ARSACS (genetic basis, protein function, and disease mechanisms) remains partial. The integrative use of organelle-based quantitative proteomics and whole-genome analysis proposed in the present study allowed identifying the affected disease-specific pathways, upstream regulators, and biological functions related to ARSACS, which exemplify a rationale for the development of improved early diagnostic strategies and alternative treatment options in this rare condition that currently lacks a cure. Our integrated results strengthen the evidence for disease-specific defects related to bioenergetics and protein quality control systems and reinforce the role of dysregulated cytoskeletal organization in the pathogenesis of ARSACS.

Unique Ataxia-Oculomotor Apraxia 2 (AOA2) in Israel with Novel Variants, Atypical Late Presentation, and Possible Identification of a Poison Exon.

AOA2 is a rare progressive adolescent-onset disease characterised by cerebellar vermis atrophy, peripheral neuropathy and elevated serum alpha-fetoprotein (AFP) caused by pathogenic bi-allelic variants in SETX, encoding senataxin, involved in DNA repair and RNA maturation. Sanger sequencing of genomic DNA, co-segregation and oxidative stress functional studies were performed in Family 1. Trio whole-exome sequencing (WES), followed by SETX RNA and qRT-PCR analysis, were performed in Family 2. Sanger sequencing in Family 1 revealed two novel in-frame SETX deletion and duplication variants in trans (c.7009_7011del; p.Val2337del and c.7369_7371dup; p.His2457dup). Patients had increased induced chromosomal aberrations at baseline and following exposure to higher mitomycin-C concentration and increased sensitivity to oxidative stress at the lower mitomycin-C concentration in cell viability test. Trio WES in Family 2 revealed two novel SETX variants in trans, a nonsense variant (c.568C > T; p.Gln190*), and a deep intronic variant (c.5549-107A > G). Intronic variant analysis and SETX mRNA expression revealed activation of a cryptic exon introducing a premature stop codon (p.Met1850Lysfs*18) and resulting in aberrant splicing, as shown by qRT-PCR analysis, thus leading to higher levels of cryptic exon activation. Along with a second deleterious allele, this variant leads to low levels of SETX mRNA and disease manifestations. Our report expands the phenotypic spectrum of AOA2. Results provide initial support for the hypomorphic nature of the novel in-frame deletion and duplication variants in Family 1. Deep-intronic variant analysis of Family 2 variants potentially reveals a previously undescribed poison exon in the SETX gene, which may contribute to tailored therapy development.