Patients’ Perspective in Hereditary Ataxia

Hereditary ataxia represents a heterogeneous group of rare disorders with the chronic progression of motor symptoms that often become debilitating. Many forms include additional neurological, cognitive, or other symptoms. Most of these disorders lack specific treatment. We aimed to investigate aspects of patients’ quality of life, experiences, and expectations. Patients with a diagnosis of hereditary ataxia were identified from our center’s diagnostic register, direct referrals, and from a patient organization. We designed a questionnaire with 32 multiple-choice or open-ended questions on disability and impairment of daily life activities, the perceived effect of symptomatic and supportive therapies, coping strategies, and how they used and experienced various sources of information about their neurological disease. We also included the EQ-5D-3L quality-of-life instrument. Results were analyzed statistically for gender, age, and groups with and without a genetic diagnosis, and were compared to published data from the general population. Seventy-five patients returned the questionnaire. Patients reported considerable disease-related disability and impairment and had significantly lower quality-of-life scores than the general population. Physiotherapy and support from family or friends were important for patients’ overall well-being. Patients with a genetic diagnosis had a lower average age at onset and felt more well-informed about their disease than patients without a genetic diagnosis. Patients used internet sources but relied primarily on their doctors to obtain information about their disease. Our study provides insights into hereditary ataxia patients’ experiences that can lead to improvements in medical and nursing care for these patients

Neurocognitive and cerebellar function in ADHD, autism and spinocerebellar ataxia

The cerebellum plays a major role in balance, motor control and sensorimotor integration, but also in cognition, language, and emotional regulation. Several neuropsychiatric disorders such as attention deficit-hyperactivity disorder (ADHD), autism spectrum disorder (ASD), as well as neurological diseases such as spinocerebellar ataxia type 3 (SCA3) are associated with differences in cerebellar function. Morphological abnormalities in different cerebellar subregions produce distinct behavioral symptoms related to the functional disruption of specific cerebro-cerebellar circuits. The specific contribution of the cerebellum to typical development may therefore involve the optimization of the structure and function of cerebro-cerebellar circuits underlying skill acquisition in multiple domains. Here, we review cerebellar structural and functional differences between healthy and patients with ADHD, ASD, and SCA3, and explore how disruption of cerebellar networks affects the neurocognitive functions in these conditions. We discuss how cerebellar computations contribute to performance on cognitive and motor tasks and how cerebellar signals are interfaced with signals from other brain regions during normal and dysfunctional behavior. We conclude that the cerebellum plays a role in many cognitive functions. Still, more clinical studies with the support of neuroimaging are needed to clarify the cerebellum's role in normal and dysfunctional behavior and cognitive functioning

New generation genetic testing entering the clinic

New generation sequencing (NGS) genetic testing is a powerful diagnostic tool and is increasingly used in the clinical workup of patients, especially in unusual presentations or where a positive family history suggests heritable disease. This review addresses the NGS technologies Targeted sequencing (TS), Whole exome sequencing (WES), Whole genome sequencing (WGS), and the use of gene panels or gene lists for clinical diagnostic purposes. These methods primarily assess nucleotide sequence but can also detect copy number variants and many tandem repeat expansions, greatly simplifying diagnostic algorithms for movement disorders. Studies evaluating the efficacy of NGS in diagnosing movement disorders have reported a diagnostic yield of up to 10.1% for familial and 15.7% for early-onset PD, 11.7–37.5% for dystonia, 12.1–61.8% for ataxia/spastic paraplegia and 11.3–28% for combined movement disorders. Patient selection and stringency in the interpretation of the detected variants and genotypes affect diagnostic yield. Careful comparison of the patient's or family's disease features with the previously reported phenotype associated with the same variant or gene can avoid false-positive diagnoses, although some genes are implicated in various phenotypes. Moving from TS to WES and WGS increases the number of patients correctly diagnosed, but for many patients, a genetic cause cannot be identified today. However, new genetically defined entities are discovered at rapid pace, and genetic databases and our knowledge of genotype-phenotype correlations expand steadily. We discuss the need for clear communication of genetic results and suggest a list of aspects to consider when reporting neurogenetic disorders using NGS testing

Oral therapy for riboflavin transporter deficiency - What is the regimen of choice?

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Ataxia-pancytopenia syndrome with SAMD9L mutations

Abstract Objective: We describe the neurologic, neuroradiologic, and ophthalmologic phenotype of 1 Swedish and 1 Finnish family with autosomal dominant ataxia-pancytopenia (ATXPC) syndrome and SAMD9L mutations. Methods: Members of these families with germline SAMD9L c.2956C>T, p.Arg986Cys, or c.2672T>C, p.Ile891Thr mutations underwent structured interviews and neurologic and ophthalmologic examinations. Neuroimaging was performed, and medical records were reviewed. Previous publications on SAMD9L-ATXPC were reviewed. Results: Twelve individuals in both families were affected clinically. All mutation carriers examined had balance impairment, although severity was very variable. All but 1 had nystagmus, and all but 1 had pyramidal tract signs. Neurologic features were generally present from childhood on and progressed slowly. Two adult patients, who experienced increasing clumsiness, glare, and difficulties with gaze fixation, had paracentral retinal dysfunction verified by multifocal electroretinography. Brain MRI showed early, marked cerebellar atrophy in most carriers and variable cerebral periventricular white matter T2 hyperintensities. Two children were treated with hematopoietic stem cell transplantation for hematologic malignancies, and the neurologic symptoms of one of these worsened after treatment. Three affected individuals had attention deficit hyperactivity disorder or cognitive problems. Retinal dysfunction was not previously reported in individuals with ATXPC. Conclusions: The neurologic phenotype of this syndrome is defined by balance or gait impairment, nystagmus, hyperreflexia in the lower limbs and, frequently, marked cerebellar atrophy. Paracentral retinal dysfunction may contribute to glare, reading problems, and clumsiness. Timely diagnosis of ATXPC is important to address the risk for severe hemorrhage, infection, and hematologic malignancies inherent in this syndrome; regular hematologic follow-up might be beneficial

Gain-of-function SAMD9L mutations cause a syndrome of cytopenia, immunodeficiency, MDS and neurological symptoms

Several monogenic causes of familial myelodysplastic syndrome (MDS) have recently been identified. We studied two families with cytopenia, predisposition to MDS with chromosome 7 aberrations, immunodeficiency, and progressive cerebellar dysfunction. Genetic studies uncovered heterozygous missense mutations in SAMD9L, a tumor suppressor gene located on chromosome arm 7q. Consistent with a gain-of-function effect, ectopic expression of the two identified SAMD9L mutants decreased cell proliferation relative to wild-type protein. Of the ten individuals identified heterozygous for either SAMD9L mutation, three developed MDS upon loss of the mutated SAMD9L allele following intracellular infections associated with myeloid, B and NK cell deficiency. Five other individuals, three with spontaneously resolved cytopenic episodes in infancy, harbored hematopoietic revertant mosaicism by uniparental disomy of 7q with loss of the mutated allele or additional in cis SAMD9L truncating mutations. Examination of one individual indicated that somatic reversions were postnatally selected. Somatic mutations were tracked to CD34(+) hematopoietic progenitor cell populations, being further enriched in B and NK cells. Stimulation of these cell types with interferon (IFN)-α or -γ induced SAMD9L expression. Clinically, revertant mosaicism was associated with milder disease, yet neurological manifestations persisted in three individuals. Two carriers also harbored a rare, in trans germline SAMD9L missense loss-of-function variant, potentially counteracting the SAMD9L mutation. Our results demonstrate that gain-of-function mutations in the tumor suppressor SAMD9L cause cytopenia, immunodeficiency, variable neurological presentation, and predisposition to MDS with -7/del(7q), where hematopoietic revertant mosaicism commonly ameliorated clinical manifestations. The findings suggest a role for SAMD9L in regulating IFN-driven, demand-adapted hematopoiesis

Tau and neurofilament light-chain as fluid biomarkers in spinocerebellar ataxia type 3

BACKGROUND AND PURPOSE: Clinical trials in spinocerebellar ataxia type 3 (SCA3) will require biomarkers for use as outcome measures.METHODS: To evaluate total tau (t-tau), glial fibrillary acidic protein (GFAP), ubiquitin carboxy-terminal hydrolase L1 (UCHL1) and neurofilament light-chain (NfL) as fluid biomarkers in SCA3, ATXN3 mutation carriers (n = 143) and controls (n = 172) were clinically assessed, and the plasma concentrations of the four proteins were analysed on the Simoa HD-1 platform. Eleven ATXN3 mutation carrier cerebrospinal fluid samples were analysed for t-tau and phosphorylated tau (p-tau181 ). A transgenic SCA3 mouse model (MJDTg) was used to measure cerebellar t-tau levels.RESULTS: Plasma t-tau levels were higher in mutation carriers below the age of 50 compared to controls, and the Inventory of Non-Ataxia Signs was associated with t-tau in ataxic patients (p = 0.004). Pre-ataxic carriers showed higher cerebrospinal fluid t-tau and p-tau181 concentrations compared to ataxic patients (p = 0.025 and p = 0.014, respectively). Cerebellar t-tau was elevated in MJDTg mice compared to wild-type (p = 0.033) only in the early stages of the disease. GFAP and UCHL1 did not show higher levels in mutation carriers compared to controls. Plasma NfL concentrations were higher in mutation carriers compared to controls, and differences were greater for younger carriers. The Scale for the Assessment and Rating of Ataxia was the strongest predictor of NfL in ataxic patients (p < 0.001).CONCLUSION: Our results suggest that tau might be a marker of early disease stages in SCA3. NfL can discriminate mutation carriers from controls and is associated with different clinical variables. Longitudinal studies are required to confirm their potential role as biomarkers in clinical trials

Toward allele-specific targeting therapy and pharmacodynamic marker for spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3 (SCA3), caused by a CAG repeat expansion in the ataxin-3 gene (ATXN3), is characterized by neuronal polyglutamine (polyQ) ATXN3 protein aggregates. Although there is no cure for SCA3, gene-silencing approaches to reduce toxic polyQ ATXN3 showed promise in preclinical models. However, a major limitation in translating putative treatments for this rare disease to the clinic is the lack of pharmacodynamic markers for use in clinical trials. Here, we developed an immunoassay that readily detects polyQ ATXN3 proteins in human biological fluids and discriminates patients with SCA3 from healthy controls and individuals with other ataxias. We show that polyQ ATXN3 serves as a marker of target engagement in human fibroblasts, which may bode well for its use in clinical trials. Last, we identified a single-nucleotide polymorphism that strongly associates with the expanded allele, thus providing an exciting drug target to abrogate detrimental events initiated by mutant ATXN3. Gene-silencing strategies for several repeat diseases are well under way, and our results are expected to improve clinical trial preparedness for SCA3 therapies