Ayudas diagnósticas y diagnóstico diferencial de la enfermedad de Pompe / Diagnostic aids and differential diagnosis of Pompe disease

Introducción: La enfermedad de Pompe (EP) o glucogenosis tipo II es una enfermedad autosómica recesiva causada por mutaciones en el gen GAA que codifica para la proteína alfa-1,4-glucosidasa. Su deficiencia lleva a un almacenamiento anormal de glucógeno en los lisosomas de varias células, a través de los diferentes tejidos, lo que causa un compromiso musculoesquelético predominante. Contenidos: Los fenotipos de la enfermedad dependen de las variantes genéticas y de los niveles de la actividad enzimática residual. La enfermedad se presenta como EP de inicio infantil, EP de inicio tardío y EP intermedio, por lo que es de suma importancia su diagnóstico temprano, por medio de estudios moleculares como la secuenciación de Sanger y la secuenciación de nueva generación. Conclusiones: Se ha demostrado, mediante diferentes estudios, que las variaciones genéticas pueden diferir entre etnias, y es importante su caracterización molecular para determinar el tratamiento más adecuado, de acuerdo con el estado del material inmunológico de reacción cruzada (CRIM).

Introduction: Pompe disease (PD) or Glycogenosis Type II is a rare autosomal recessive disease caused by mutations in the GAA gene that codes for the alpha-1,4-glucosidase protein. Its deficiency leads to abnormal glycogen storage in the lysosomes of various cells throughout the different tissues causing a predominant musculoskeletal compromise. Contents: The phenotypes of the disease depend on the genetic variants and the levels of residual enzyme activity, presenting as infantile-onset PD, late-onset PD, and intermediate PD; Therefore, early diagnosis of the disease through molecular studies such as Sanger sequencing and new generation sequencing is of utmost importance. Conclusions: It has been shown through different studies that genetic variations can vary between ethnic groups and the molecular characterization of the variants is important to determine the most appropriate treatment depending on the state of the cross-reactive immunological material (CRIM)

Preimplantation genetic testing in assisted reproduction.

In the last years technologies have been developed that allow obtaining genetic information in less time and at lower cost, revolutionizing the genetic diagnosis in reproductive medicine, with availability of genetic tests from conception. High throughput sequencing analyses have increased the ability to detect embryos with genetic diseases, which has contributed to the better selection of embryos for in-vitro fertilization and, therefore, better reproductive outcomes. The preimplantation genetic testing (PGT) includes three subcategories of PGT for aneuploidies (PGT-A), PGT for single gene/monogenic disorders (PGT-M), and PGT for chromosome structural rearrangements (PGT-SR). This review provides an overview of the evolution of preimplantation genetic testing, the advantages and disadvantages of these technologies and their applicability in reproductive medicine as well as a description of the legislation and bioethics aspects. Advances in preimplantation genetic testing are changing clinical practice, posing new challenges for genetic counseling and alternative plausible to substantially reduce the risk of an adverse reproductive outcome related to the transfer of abnormal embryos. Despite the overall important implantation rates achieved following transfer of euploid embryos, PGT-A did not improve overall pregnancy outcomes in all women. There is a definite need for studies to identify the causes of why not all euploid embryos implant. Also, debate continues regarding the accuracy and the safety of this approach, and the currently available evidence is insufficient to support PGT-A in routine clinical practice. The general recommendation is that PGT-A, PGT-M and PGT-SR should be guided according to the antecedents of the couples.

Association between risk polymorphisms for neurodegenerative diseases and cognition in colombian patients with frontotemporal dementia.

Frontotemporal dementia (FTD) is a heterogeneous neurodegenerative disease of presenile onset. A better characterization of neurodegenerative disorders has been sought by using tools such as genome-wide association studies (GWAS), where associations between single nucleotide polymorphisms (SNPs) and cognitive profiles could constitute predictive biomarkers for these diseases. However, in FTD, associations between genotypes and cognitive phenotypes are yet to be explored. Here, we evaluate a possible relationship between genetic variants and some cognitive functions in an FTD population. Methodology: A total of 47 SNPs in genes associated with neurodegenerative diseases were evaluated using the Sequenom MassARRAY platform along with their possible relationship with performance in neuropsychological tests in 105 Colombian patients diagnosed with FTD. Results and discussion: The SNPs rs429358 (APOE), rs1768208 (MOBP), and rs1411478 (STX6), were identified as risk factors for having a low cognitive performance in inhibitory control and phonological verbal fluency. Although the significance level was not enough to reach the corrected alpha for multiple comparison correction, our exploratory data may constitute a starting point for future studies of these SNPs and their relationship with cognitive performance in patients with a probable diagnosis of FTD. Further studies with an expansion of the sample size and a long-term design could help to explore the predictive nature of the potential associations we identified.

Experiences of the Molecular Diagnosis of Fragile X Syndrome in Ecuador.

Fragile X syndrome (FXS) is the most common cause of hereditary intellectual disability and the second most common cause of intellectual disability of genetic etiology. This complex neurodevelopmental disorder is caused by an alteration in the CGG trinucleotide expansion in fragile X mental retardation gene 1 (FMR1) leading to gene silencing and the subsequent loss of its product: fragile X mental retardation protein 1 (FMRP). Molecular diagnosis is based on polymerase chain reaction (PCR) screening followed by Southern blotting (SB) or Triplet primer-PCR (TP-PCR) to determine the number of CGG repeats in the FMR1 gene. We performed, for the first time, screening in 247 Ecuadorian male individuals with clinical criteria to discard FXS. Analysis was carried out by the Genetics Service of the Hospital de Especialidades No. 1 de las Fuerzas Armadas (HE-1), Ecuador. The analysis was performed using endpoint PCR for CGG fragment expansion analysis of the FMR1 gene. Twenty-two affected males were identified as potentially carrying the full mutation in FMR1 and thus diagnosed with FXS that is 8.1% of the sample studied. The average age at diagnosis of the positive cases was 13 years of age, with most cases from the geographical area of Pichincha (63.63%). We confirmed the familial nature of the disease in four cases. The range of CGG variation in the population was 12-43 and followed a modal distribution of 27 repeats. Our results were similar to those reported in the literature; however, since it was not possible to differentiate between premutation and mutation cases, we can only establish a molecular screening approach to identify an expanded CGG repeat, which makes it necessary to generate national strategies to optimize molecular tests and establish proper protocols for the diagnosis, management, and follow-up of patients, families, and communities at risk of presenting FXS.

Analysis of Heritability Across the Clinical Phenotypes of Frontotemporal Dementia and the Frequency of the C9ORF72 in a Colombian Population.

Frontotemporal dementia (FTD) is a highly heritable condition. Up to 40% of FTD is familial and an estimated 15% to 40% is due to single-gene mutations. It has been estimated that the G4C2 hexanucleotide repeat expansions in the C9ORF72 gene can explain up to 37.5% of the familial cases of FTD, especially in populations of Caucasian origin. The purpose of this paper is to evaluate hereditary risk across the clinical phenotypes of FTD and the frequency of the G4C2 expansion in a Colombian cohort diagnosed with FTD. Methods: A total of 132 FTD patients were diagnosed according to established criteria in the behavioral variant FTD, logopenic variant PPA, non-fluent agrammatic PPA, and semantic variant PPA. Hereditary risk across the clinical phenotypes was established in four categories that indicate the pathogenic relationship of the mutation: high, medium, low, and apparently sporadic, based on those proposed by Wood and collaborators. All subjects were also examined for C9ORF72 hexanucleotide expansion (defined as >30 repetitions). Results: There were no significant differences in the demographic characteristics of the patients between the clinical phenotypes of FTD. The higher rate phenotype was bvFTD (62.12%). In accordance with the risk classification, we found that 72 (54.4%) complied with the criteria for the sporadic cases; for the familial cases, 23 (17.4%) fulfilled the high-risk criteria, 23 (17.4%) fulfilled the low risk criteria, and 14 (10.6%) fulfilled the criteria to be classified as subject to medium risk. C9ORF72 expansion frequency was 0.76% (1/132). Conclusion: The FTD heritability presented in this research was very similar to the results reported in the literature. The C9ORF72 expansion frequency was low. Colombia is a triethnic country, with a high frequency of genetic Amerindian markers; this shows consistency with the present results of a low repetition frequency. This study provides an initial report of the frequency for the hexanucleotide repeat expansions in C9ORF72 in patients with FTD in a Colombian population and paves the way for further study of the possible genetic causes of FTD in Colombia.