The Phenotypic Spectrum of Spinocerebellar Ataxia Type 19 in a Series of Latin American Patients.

Spinocerebellar ataxia 19 (SCA19) represents a rare autosomal dominant genetic disorder resulting in progressive ataxia and cerebellar atrophy. SCA19 is caused by variants in the KCND3 gene, which encodes a voltage-gated potassium channel subunit essential for cerebellar Purkinje cell function. We describe six cases from Chile and Mexico, representing the largest report on SCA19 in Latin America. These cases encompass a range of clinical presentations, highlighting the phenotypic variability within SCA19 from an early-onset, severe disease to a late-onset, slowly progressive condition with normal lifespan. While some patients present with pure ataxia, others also show cognitive impairment, dystonia, and other neurological symptoms. The correlations between specific KCND3 variants and phenotypic outcomes are complex and warrant further investigation. As the genomic landscape of spinocerebellar ataxias evolves, comprehensive genetic testing is becoming pivotal in improving diagnostic accuracy. This study contributes to a better understanding of the clinical spectrum of SCA19, laying the groundwork for further genotype-phenotype correlations and functional studies to elucidate the underlying pathophysiology.

Association of variants in the ABCB1, CYP2C19 and CYP2C9 genes for Juvenile Myoclonic Epilepsy.

Juvenile myoclonic epilepsy (JME) is the most common of the generalized genetic epilepsies, with multiple causal and susceptibility genes; however, its etiopathogenesis is mainly unknown. The toxic effects caused by xenobiotics in cells occur during their metabolic transformation, mainly by enzymes belonging to cytochrome P450. The elimination of these compounds by transporters of the ABC type protects the central nervous system, but their accumulation causes neuronal damage, resulting in neurological diseases. The present study has sought the association between single nucleotide genetic variants of the CYP2C9, CYP2C19, and ABCB1 genes and the development of JME in patients compared to healthy controls. The CC1236 and GG2677 genotypes of ABCB1 in women; allele G 2677, genotypes GG 2677 and CC 3435 in men; the CYP2C19*2A allele, and the CYP2C19*3G/A genotype in both sexes were found to be risk factors for JME. Furthermore, carriers of the TTGGCC genotype combination of the ABCB1 gene (1236/2677/3435) have a 10.5 times higher risk of developing JME than non-carriers. Using the STRING database, we found an interaction between the proteins encoded by these genes and other possible proteins. These findings indicate that the CYP450 system and ABC transporters could interact with other genes in the JME.

An Exploratory Survey on the Care for Ataxic Patients in the American Continents and the Caribbean.

Little is known about access of rare disease carriers to health care. To increase this knowledge, the Pan American Hereditary Ataxia Network (PAHAN) conducted an exploratory survey about care for hereditary ataxias in American continents and the Caribbean. A questionnaire was sent to health professionals about the hereditary ataxias identified; access to care; and local teaching and research. The number of ataxics under current care per 100,000 inhabitants was subtracted from the expected overall prevalence of 6/100,000, to estimate the prevalence of uncovered ataxic patients. Local Human Development Indexes (HDI) were used to measure socio-economic factors. Twenty-six sites participated. Twelve sites had very high, 13 had high, and one site had medium HDI. Participants reported on 2239 and 602 patients with spinocerebellar ataxias and recessive forms under current care. The number of patients under current care per inhabitants varied between 0.14 and 12/100,000. The estimated prevalence of uncovered ataxic patients was inversely proportional to HDIs (rho = 0.665, p = 0.003). Access to diagnosis, pre-symptomatic tests, and rehabilitation were associated with HDIs. More and better molecular diagnostic tools, protocols and guidelines, and professional training for ataxia care were the top priorities common to all respondents. Evidence of inequalities was confirmed. Lower HDIs were associated with high potential numbers of uncovered ataxic subjects, and with lack of molecular diagnosis, pre-symptomatic testing, and rehabilitation. More and better diagnostic tools, guidelines, and professional training were priorities to all sites. PAHAN consortium might help with the last two tasks.

Low quality of life, increased number of anti-seizure drugs, and the lack of caregiver support are associated with internalized stigma in adult Mexican patients with epilepsy.

BACKGROUND: People with epilepsy (PWE) have been subject to stigma throughout history, a factor that could compromise their performance in daily life. In Mexico, little is known about the factors that may be affecting internalized stigma. OBJECTIVE: To evaluate the internalized stigma in adult PWE, its relationship with the quality of life, cognitive and depressive symptomatology, and clinical-demographic characteristics. MATERIAL AND METHODS: We conducted a cross-sectional study with a consecutive sampling approach in patients with epilepsy treated at the National Institute of Neurology and Neurosurgery Manuel Velasco Suárez (NINNMVS). Sociodemographic and clinical data, depressive symptomatology (Beck's depression inventory, DBI), cognition (MoCA test), quality of life (QOLIE-31 scale), and internalized stigma (King's internalized stigma scale, ISS) were evaluated. Correlations were made between the continuous variables and the ISS to select those with statistical significance and include them in a multiple linear regression model, along with the dummy variables, to explain internalized stigma. RESULTS: Of 128 patients, 74 (58%) were women; 38% of the patients had more than 20 years of epilepsy evolution. In addition, 39% presented depressive symptoms, and around 60% manifested a possible cognitive impairment. The variables that showed statistical significance concerning the ISS were selected along with dummy variables for multiple linear regression analysis. The resultant model considers the QOLIE-31 total score (ß = -0.489), the number of anti-seizure drugs (ASD, ß = 0.253), and those patients without caregiver support (ß = -0.166) with an adjusted R2 value of 0.316. CONCLUSIONS: A diminishing quality of life, an increased number of ASD, and patients without caregiver support influence a slight to moderate variation of internalized stigma in Mexican PWE. Therefore, it is necessary to continue studying other possible factors that influence internalized stigma to generate effective strategies to reduce its negative effects on PWE.

Clinical and Molecular Findings of Intermediate Allele Carriers in the HTT Gene from the Mexican Mestizo Population.

INTRODUCTION: There are reports of different clinical statuses in carriers of intermediate alleles (IAs) of CAG trinucleotide repeats in the HTT gene, from individuals affected by a clinical picture indistinguishable from Huntington's disease (HD) to those without manifestations. Therefore, the possible clinical significance of these alleles has been widely debated. OBJECTIVES: The aim of this study was to describe general and clinical features and discard HD phenocopies by molecular assessment in a case series of IA carriers on the HTT gene of a laboratory sample from a neurological center in Mexico. METHODS: We selected individuals who had previously been tested for the HTT gene expansion, which resulted in IAs. Clinical information was obtained from medical records, and molecular analysis of the JPH3, PRNP, and TBP genes was performed only in IA carriers with clinical manifestations. In addition, two patients with IA and acanthocytes were evaluated by whole-exome sequencing. The scientific and ethical committees of the National Institute of Neurology and Neurosurgery Manuel Velasco Suárez (NINNMVS) approved this study. RESULTS: From 1994 to 2019, the Genetics Department of the NINNMVS confirmed 34 individuals with IAs, 15 of whom belonged to 11 families with HD (IA-HD) and 19 of whom had no family history of HD (IA-non-HD). We found a high proportion of manifestations of the HD phenotypic spectrum in the IA-non-HD subgroup. In addition, among the 20 samples of IA carriers with manifestations molecularly evaluated, we identified two unrelated subjects with CAG/CTG repeat expansions on the JPH3 gene, confirming HD-like 2 (HDL2), and one patient with the homozygous pathogenic c.3232G>T variant (p.Glu1078Ter) in the VPS13A gene, demonstrating choreoacanthocytosis. DISCUSSION/CONCLUSION: Our results show the most extensive series of subjects with IAs and clinical manifestations. In addition, we identify three HD phenocopies, two HDL2 cases, and one choreoacanthocytosis case. Therefore, we emphasize evaluating other HD phenocopies in IA carriers with clinical manifestations whose family background is not associated with HD.

Presymptomatic Testing for Huntington's Disease in Mexico: 28 Years of Experience.

INTRODUCTION: Huntington's disease (HD) is a genetic neurodegenerative disorder with dominant inheritance. Our center in Mexico City has offered presymptomatic testing (PT) since 1995. OBJECTIVE: To describe the main clinical and demographic characteristics of at-risk HD individuals who applied to the PT program, the reasons for seeking it, and the molecular results. METHODS: A cross-sectional study was conducted with sociodemographic and clinical data of all PT applicants from 1995-2023. Reasons for seeking PT were assessed using a modified questionnaire. In addition, anxiety, and depressive symptoms before and after PT were evaluated with Beck's instruments; cognitive impairment (CI) was assessed with the Mini-Mental State Examination (MMSE) and molecular results. RESULTS: 214 people applied for PT (2.1% of the at-risk population identified in our center); 63% were women (mean age of 37.11 years). 204 (95.3%) were accepted and 190 received results. 70% indicated that the main reason for applying for PT was to inform their offspring about the risk of inheriting HD. Significant differences were observed in the reasons for seeking PT by age group. Although some subjects received treatment, Beck's instrument scores did not indicate special attention or pharmacological treatment. The MMSE showed probable CI in 20 subjects. Of those who received results, 37% were carriers of a full penetrance allele. CONCLUSION: Our center has the only formal PT program for HD in Mexico. The reasons for seeking PT are varied and age-related. Although PT is offered to all subjects at risk for HD, uptake remains low.

Saccades, pupil response and blink abnormalities in Huntington's disease patients during free viewing.

OBJECTIVE: Video-based eye tracking was used to investigate saccade, pupil, and blink abnormalities among patients with Huntington's disease (HD) who watched sequences of short videos. HD, an autosomal dominant neurodegenerative disorder resulting from a CAG mutation on chromosome 4, produces motor and cognitive impairments including slow or irregular eye movements, which have been studied using structured tasks. METHODS: To explore how HD affects eye movements under instruction free conditions, we assessed 22 HD patients and their age matched controls in a 10-minute video-based free viewing task. RESULTS: Patients with HD experienced a significant reduction in saccade exploration rate following video clip transitions, an increase in pupil reactions to luminance changes after clip transitions, and a significant higher blink rate throughout the task compared to the control group. CONCLUSIONS: These results show that HD has a significant impact on how patients visually explore and respond to their environment under unconstrained and ecologically natural conditions. SIGNIFICANCE: Eye tracking in HD patients revealed saccadic, pupil, and blink abnormalities in early HD patients, suggestive of brain circuitry abnormalities that probably involve brain stem deficits. Further research should explore the impact of these changes on the quality of life of the patients affected by the disease.

Relationship between APOE, PER2, PER3 and OX2R Genetic Variants and Neuropsychiatric Symptoms in Patients with Alzheimer's Disease.

Alzheimer's disease (AD) is characterized by the presence of neuropsychiatric or behavioral and psychological symptoms of dementia (BPSD). BPSD have been associated with the APOE_ε4 allele, which is also the major genetic AD risk factor. Although the involvement of some circadian genes and orexin receptors in sleep and behavioral disorders has been studied in some psychiatric pathologies, including AD, there are no studies considering gene-gene interactions. The associations of one variant in PER2, two in PER3, two in OX2R and two in APOE were evaluated in 31 AD patients and 31 cognitively healthy subjects. Genotyping was performed using real-time PCR and capillary electrophoresis from blood samples. The allelic-genotypic frequencies of variants were calculated for the sample study. We explored associations between allelic variants with BPSD in AD patients based on the NPI, PHQ-9 and sleeping disorders questionnaires. Our results showed that the APOE_ε4 allele is an AD risk variant (p = 0.03). The remaining genetic variants did not reveal significant differences between patients and controls. The PER3_rs228697 variant showed a nine-fold increased risk for circadian rhythm sleep-wake disorders in Mexican AD patients, and our gene-gene interaction analysis identified a novel interaction between PERIOD and APOE gene variants. These findings need to be further confirmed in larger samples.

Clozapine Long-Term Treatment Might Reduce Epigenetic Age Through Hypomethylation of Longevity Regulatory Pathways Genes.

Long-term studies have shown significantly lower mortality rates in patients with continuous clozapine (CLZ) treatment than other antipsychotics. We aimed to evaluate epigenetic age and DNA methylome differences between CLZ-treated patients and those without psychopharmacological treatment. The DNA methylome was analyzed using the Infinium MethylationEPIC BeadChip in 31 CLZ-treated patients with psychotic disorders and 56 patients with psychiatric disorders naive to psychopharmacological treatment. Delta age (Δage) was calculated as the difference between predicted epigenetic age and chronological age. CLZ-treated patients were stratified by sex, age, and years of treatment. Differential methylation sites between both groups were determined using linear regression models. The Δage in CLZ-treated patients was on average lower compared with drug-naive patients for the three clocks analyzed; however, after data-stratification, this difference remained only in male patients. Additional differences were observed in Hannum and Horvath clocks when comparing chronological age and years of CLZ treatment. We identified 44,716 differentially methylated sites, of which 87.7% were hypomethylated in CLZ-treated patients, and enriched in the longevity pathway genes. Moreover, by protein-protein interaction, AMPK and insulin signaling pathways were found enriched. CLZ could promote a lower Δage in individuals with long-term treatment and modify the DNA methylome of the longevity-regulating pathways genes.

Clinical and Molecular Features of First Mexican Friedreich's Ataxia Patients with Compound Heterozygous FXN Mutations.

BACKGROUND: Friedreich's ataxia (FRDA) is caused by homozygous GAA repeat expansions or compound heterozygous (CH) mutations in FXN gene. Its broad clinical spectrum makes it difficult to identify, thus an accurate diagnosis can only be made by genetic testing. OBJECTIVE: This study aims to present data on FXN variants observed in patients with sporadic or recessive ataxia, including detailed data of the first CH Mexican patients. MATERIALS AND METHODS: One hundred and eight patients with recessive or sporadic cerebellar ataxia were referred to our institution between 2009 and 2019 for FXN molecular testing. This was achieved using a combined methodology of triplet repeat-primed PCR (polymerase chain reaction), long PCR, FXN sequencing and multiplex-ligation probe-amplification. RESULTS: Eighteen patients had a homozygous FXN genotype; whereas five were CH patients with a slow progression and phenotypic variability, including a late-onset case with spastic paraparesis, and a Charcot-Marie-Tooth-like case. CONCLUSIONS: These first Mexican CH patients pose important implications for genetic counseling and FRDA management.

Integrative Genomic-Epigenomic Analysis of Clozapine-Treated Patients with Refractory Psychosis.

Clozapine (CLZ) is the only antipsychotic drug that has been proven to be effective in patients with refractory psychosis, but it has also been proposed as an effective mood stabilizer; however, the complex mechanisms of action of CLZ are not yet fully known. To find predictors of CLZ-associated phenotypes (i.e., the metabolic ratio, dosage, and response), we explore the genomic and epigenomic characteristics of 44 patients with refractory psychosis who receive CLZ treatment based on the integration of polygenic risk score (PRS) analyses in simultaneous methylome profiles. Surprisingly, the PRS for bipolar disorder (BD-PRS) was associated with the CLZ metabolic ratio (pseudo-R2 = 0.2080, adjusted p-value = 0.0189). To better explain our findings in a biological context, we assess the protein-protein interactions between gene products with high impact variants in the top enriched pathways and those exhibiting differentially methylated sites. The GABAergic synapse pathway was found to be enriched in BD-PRS and was associated with the CLZ metabolic ratio. Such interplay supports the use of CLZ as a mood stabilizer and not just as an antipsychotic. Future studies with larger sample sizes should be pursued to confirm the findings of this study.

[ApoE polymorphisms and dopaminergic replacement therapy in Parkinson's disease]. / Polimorfismos de apoE y reemplazo dopaminérgico en enfermedad de Parkinson.

BACKGROUND: The expression of apolipoprotein E (apoE) polymorphisms has been proposed as a risk factor for early development of psychotic symptoms in patients with Parkinson's disease. The association between apoE polymorphisms and motor complications is controversial. The aim was to determine the association between apoE polymorphisms and its allele frequency with the development of complications secondary to dopaminergic replacement therapy. METHODS: We evaluated 231 patients with the diagnosis of Parkinson's disease. The presence of motor complications secondary to treatment was determined by a neurologist, and the genotypification of apoE polymorphisms was performed. Descriptive statistics and chi-squared test were used. RESULTS: Genotype ?3/?3 was expressed in 80.5 % of the sample; there was no association between genotype or allele frequency of apoE polymorphisms and the development of psychosis or dyskinesia. Patients who expressed the ?2 allele showed a tendency to develop motor fluctuations, but without reaching statistical significance (p = 0.08). CONCLUSIONS: ApoE polymorphisms are not associated with the development of complications from dopaminergic replacement therapy.

INTRODUCCIÓN: se ha propuesto que la expresión de los polimorfismos de la apolipoproteína E (apoE) es un factor predisponente para el desarrollo temprano de psicosis en los pacientes con enfermedad de Parkinson. La relación entre el genotipo de la apoE y el desarrollo de complicaciones motoras es controvertida. El objetivo de esta investigación fue determinar la relación entre los polimorfismos de la apoE y su frecuencia alélica y el desarrollo de complicaciones secundarias al reemplazo dopaminérgico. MÉTODOS: se evaluaron 231 pacientes con diagnóstico de enfermedad de Parkinson. La presencia de complicaciones fue determinada por un neurólogo y se realizó la genotipificación de los polimorfismos de la apoE. Se utilizó la chi cuadrada para determinar la relación entre la presencia o ausencia de las complicaciones estudiadas y el genotipo de la apoE. RESULTADOS: se identificó el genotipe ?3/?3 en 80.5 % de la muestra. No existió relación entre el genotipo o la frecuencia alélica de los polimorfismos de la apoE y el desarrollo de psicosis o discinesias. Los pacientes que expresaron el alelo ?2 mostraron una tendencia al desarrollo de fluctuaciones, pero sin significación estadística (p = 0.08). CONCLUSIONES: los polimorfismos de la apoE no se relacionaron con el desarrollo de complicaciones derivadas del reemplazo dopaminérgico. El tratamiento de la enfermedad de Parkinson se basa principalmente en la administración de precursores de la dopamina (como la levodopa) o de agonistas dopaminérgicos.