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A wide phenotypic spectrum exists among DMD patients, with genetic modifiers seen as a putative cause of this variability. The main aim was to evaluate the effect of 4 genetic modifiers and the location of DMD variants on disease severity in a DMD Argentine cohort. A secondary objective was to unravel the current validation status of the tested loci. Two groups of patients with extreme phenotypes (Severe/Mild) were defined based on the age at loss of ambulation. SNVs in SPP1, LTBP4, CD40, and ACTN3 were genotyped, and their distribution was compared between groups using Chi-square or Fisher exact tests. Concurrent effects with glucocorticoids treatment, DMD mutation location (proximal/distal) and the other loci were evaluated by multivariate logistic regression. Additionally, we performed a systematic literature review to summarize and interpret the impact of modifiers on various DMD traits. ACTN3-rs1815739 was the only modifier loci of DMD progression in our cohort. A concurrent damaging effect between DMD mutation and ACTN3 was detected, identifying a possible interaction between distal variants and ACTN3 TT-genotype that need to be validated in a larger cohort. The systematic review showed agreement in the results when significant differences were reported. The employment of extreme DMD phenotypic groups was an innovative approach for identifying risk loci for disease severity. The interaction between DMD mutation location and ACTN3, if confirmed, could help to avoid confounding elements in assembling study cohorts for clinical trials. Finally, this report major highlight is being the first study conducted on an Argentine and Latin-American population. [ABSTRACT FROM AUTHOR]

Pompe disease is a rare autosomal recessive disorder caused by mutations in GAA , leading to enzyme acid alpha-glucosidase deficiency. Diagnosis is challenging due to disease's variable presentation and overlap with other conditions, delaying diagnosis. Historically, diagnosis relied on measuring alpha-glucosidase activity in blood spots, but advancements in NGS technology have improved diagnostic accuracy. However, interpreting genetic variants can be complex, especially in the presence of pseudodeficiency alleles, which can mimic disease-causing mutations. Here, we introduce 2 cases carrying the same pseudodeficiency allele, also known as GAA2 , NM_000152.5(GAA): c.271G>A (p.Asp91Asn). The first one, a recently published controversial case of a heterozygous mummy from 700 years ago, where authors classified the variant as pathogenic and, therefore, raised confusion in the scientific community. The second one, a homozygous patient with symptoms compatible with Pompe disease and low acid alpha-glucosidase activity, who was referred to our laboratory. Our main aim was to highlight the importance of the correct classification of variants by using variant GAA : c.271G>A as a model. Therefore, our goal was to demonstrate that, based on international standards, this variant cannot be classified as pathogenic given the existing evidence. Also, we pursue the genetic diagnosis of the second patient. The analysis of the GAA variant was performed applying international consensus guidelines (ACMG-AMP). A thorough revision was done together with the Lysosomal Diseases Variant Curation Expert Panel. The second patient was studied by NGS and its results were analyzed using a panel including all known NMD genes. Thus, we demonstrated that GAA : c.271G>A is classified as benign. Additionally, our patient, initially suspected to have Pompe disease, resulted a carrier of a pathogenic variant in PABPN1, associated with another condition. In literature, this pseudodeficiency variant causes confusion, due to inaccurate results of enzymatic activity. Based on the evidence available to date, the variant GAA : c.271G>A meets the criteria to be classified as benign for Pompe disease. Additionally, the second patient was found to carry a heterozygous PABPN1 pathogenic variant associated with Oculopharyngeal muscular dystrophy. This diagnosis fit the clinical features better than the initially suspected to have Pompe disease. Here, we demonstrated the importance of expanding genetic analysis in presence of pseudodeficiency alleles that can mask the true cause of the disease. Finally, this highlights the fact that an accurate diagnosis should adhere to international consensus on variant curation to avoid misdiagnosis, which could result in inadequate care and risky medical decisions. [ABSTRACT FROM AUTHOR]

DMD-carriers were traditionally considered asymptomatic given the X-linked recessive inheritance pattern of these diseases. Yet, it has recently been discovered that they exhibit different levels of muscle involvement. This study aimed to characterize and compare the muscle structure on MRI of DMD-carriers and a control group. Secondly, we pursue a correlation between levels of muscle involvement and clinical manifestations, creatine kinase (CK) levels, DMD molecular alteration and X-chromosome inactivation (XCI) patterns. We enrolled 30 genetically confirmed DMD female carriers and 30 healthy non-carrier controls, BMI and age matched. All individuals underwent whole-body MRI, where semi-quantitative scales were used to assess muscle edema, trophism and fatty infiltration. Neurological examination, Serum CK measurement, DMD genetic screening, and XCI studies were only performed on the DMD-carriers. Statistically significant differences in muscle involvement were observed between DMD-carriers and the control group. Female carriers exhibited muscle affection in 33% of the 48 muscle groups analyzed, while the control group presented only the 10% affected. Most of the DMD-carriers' implicated muscles showed mild atrophy and mild to moderate fatty infiltration. The muscles more frequently affected were gastrocnemius, gluteus maximus and soleus. No statistical correlation was found between the levels or pattern of muscle involvement on MRI and the neurological examination, CK values, type of genetic variant and XCI patterns. DMD-carriers exhibit frequent and distinctive muscle involvement patterns on MRI, questioning the conception of "asymptomatic" DMD-Carriers. These results, together with findings in other X-linked disorders, lead to a revision of the concept of asymptomatic carriers of X-linked recessive diseases and raise awareness of the need to develop best practice guidelines for the evaluation and management of these females. [ABSTRACT FROM AUTHOR]

A wide phenotypic spectrum exists among DMD patients, with genetic modifiers seen as a putative cause of this variability. The main aim was to evaluate the effect of 4 genetic modifiers and the location of DMD variants on disease severity in a DMD Argentine cohort. A secondary objective was to provide a summary of the current state of knowledge and association of the tested loci with DMD's phenotype. Two groups of patients with extreme phenotypes (Severe/Mild) were defined based on the age at loss of ambulation. SNVs in SPP1, LTBP4, CD40, and ACTN3 were genotyped, and their distribution was compared between groups using Chi-square or Fisher exact tests. Concurrent effects with glucocorticoids treatment, DMD mutation location (proximal/distal) and the other loci were evaluated by multivariate logistic regression. Additionally, we performed a systematic literature review to summarize and interpret the impact of modifiers on various DMD traits. ACTN3-rs1815739 was the only modifier loci of DMD progression in our cohort. A concurrent damaging effect between DMD mutation and ACTN3 was detected, identifying a possible interaction between distal variants and ACTN3 TT-genotype that need to be validated in a larger cohort. The systematic review showed agreement in the results when significant differences were reported. The employment of extreme DMD phenotypic groups was an innovative approach for identifying risk loci for disease severity. The interaction between DMD mutation location and ACTN3, if confirmed, could help to avoid confounding elements in assembling study cohorts for clinical trials. Finally, this report's major highlight is being the first study conducted on an Argentine and Latin-American population., Competing Interests: Declaration of Competing interest The authors Florencia Giliberto, PhD., Lilia Mesa, MD, and Alberto Dubrovsky, MD, have received honoraria/grants for either: teaching, consultation, advisory board and speaker activities from: PTC Therapeutics, Sarepta Therapeutics, Sanofi Genzyme and Biomarin. Florencia Giliberto, PhD., received research grants from PTC pharmaceuticals to perform genetic testing of the patients. The sponsor did not interfere with study design; collection, analysis and interpretation of data; writing of the manuscript and in the decision to submit the present work for publication. The remaining authors have nothing to report., (Copyright © 2024 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.)

Dystrophinopathies cover a spectrum of rare progressive X-linked muscle diseases, arising from DMD mutations. They are among the most common pediatric muscular dystrophies, being Duchenne muscular dystrophy (DMD) the most severe form. Despite the fact that there is still no cure for these serious diseases, unprecedented advances are being made for the development of therapies for DMD. Some of which are already conditionally approved: exon skipping and premature stop codon read-through. The present work aimed to characterize the mutational spectrum of DMD in an Argentinian cohort, to identify candidates for available pharmacogenetic treatments and finally, to conduct a comparative analysis of the Latin American (LA) frequencies of mutations amenable for available DMD therapies. We studied 400 patients with clinical diagnosis of dystrophinopathy, implementing a diagnostic molecular algorithm including: MLPA/PCR/Sanger/Exome and bioinformatics. We also performed a meta-analysis of LA's metrics for DMD available therapies. The employed algorithm resulted effective for the achievement of differential diagnosis, reaching a detection rate of 97%. Because of this, corticosteroid treatment was correctly indicated and validated in 371 patients with genetic confirmation of dystrophinopathy. Also, 20 were eligible for exon skipping of exon 51, 21 for exon 53, 12 for exon 45 and another 70 for premature stop codon read-through therapy. We determined that 87.5% of DMD patients will restore the reading frame with the skipping of only one exon. Regarding nonsense variants, UGA turned out to be the most frequent premature stop codon observed (47%). According to the meta-analysis, only four LA countries (Argentina, Brazil, Colombia and Mexico) provide the complete molecular algorithm for dystrophinopathies. We observed different relations among the available targets for exon skipping in the analyzed populations, but a more even proportion of nonsense variants (∼40%). In conclusion, this manuscript describes the theragnosis carried out in Argentinian dystrophinopathy patients. The implemented molecular algorithm proved to be efficient for the achievement of differential diagnosis, which plays a crucial role in patient management, determination of the standard of care and genetic counseling. Finally, this work contributes with the international efforts to characterize the frequencies and variants in LA, pillars of drug development and theragnosis., Competing Interests: The authors GF, CJ, ML, and DA have received honoraria/grants for either: teaching, consultation, advisory board and speaker activities from: PTC Therapeutics, Sarepta Therapeutics, Sanofi Genzyme and Biomarin. GF received research grants from PTC pharmaceuticals to perform genetic testing of the patients. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Luce, Carcione, Mazzanti, Buonfiglio, Dalamón, Mesa, Dubrovsky, Corderí and Giliberto.)

This work describes a family with Duchenne muscular dystrophy (DMD) with a rare case of a symptomatic pregnant woman. The main aim was to perform prenatal molecular diagnosis to provide genetic counseling. The secondary aim was to suggest the molecular mechanisms causing the complex structural variant (cxSV) identified. To accomplish this, we used a multi-technique algorithm including segregation analysis, Multiplex Ligation-dependent Probe Amplification, PCR, X-chromosome inactivation studies, microarrays, whole genome sequencing and bioinformatics. We identified a duplication of exons 38-43 in the DMD gene in all affected and obligate carrier members, proving that this was the DMD-causing mutation. We also observed a skewed X-chromosome inactivation in the symptomatic woman that explained her symptomatology. In addition, we identified a cxSV (duplication of exons 38-43 and deletion of exons 45-54) in the affected boy. The molecular characterization and bioinformatic analyses of the breakpoint junctions allowed us to identify Double Strand Breaks stimulator motifs and suggested the replication-dependent Fork Stalling and Template Switching as the most probable mechanisms leading to the duplication. In addition, the de novo deletion might have been the result of a germline inter-chromosome non-allelic recombination involving the Non-Homologous End Joining mechanism. In conclusion, the diagnostic strategy used allowed us to provide accurate molecular diagnosis and genetic counseling. In addition, the familial molecular diagnosis together with the in-depth characterization of the cxSV helped to determine the chronology of the molecular events, and propose and understand the molecular mechanisms involved in the generation of this complex rearrangement., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Dystrophinopathies are neuromuscular X-linked recessive diseases caused by mutations in the DMD gene. This study aimed to identify DMD gene small mutations by Whole Exome Sequencing (WES), in order to confirm clinical diagnosis, identify candidates for Ataluren treatment and perform carrier status testing. Furthermore, was our goal to characterize the DMD sequence variants and identify ancestral haplotypes. We analyzed 40 non-related individuals (38 affected boys with dystrophinopathy presumptive clinical diagnosis and 2 at-risk women) with negative MLPA results. Pathogenic DMD variants were found in 32 boys. Surprisingly, in another 4 patients with absence/deficiency of dystrophin in muscle biopsy, pathogenic variants were found in Limb-girdle muscular dystrophy genes. Therefore, the WES detection rate resulted ∼94% (36/38). We could identify 15 Ataluren candidates and exclude 2 at-risk women. The characterization of the occurrence and diversity of DMD sequence variants from our cohort and from LOVD database, revealed no hotspots but showed exons/introns unlikely to carry small molecular alterations and exons presenting a greater mutagenic abundance than others. Also, we have detected the existence of 2 co-segregating haplotypes blocks. Finally, this work represents the first DMD gene small mutations screening applying WES in an argentine cohort, contributes with the characterization of our population and collaborates with the DMD small mutation's knowledge., (Copyright © 2018 Elsevier B.V. All rights reserved.)