Merosin-deficient Muscular Dystrophy Research Articles

Diagnostic strategies for muscular dystrophies: a cross-sectional study

Background Muscular dystrophies are a wide heterogeneity group of neuromuscular diseases that very often constitutes a challenge for clinicians to perform an adequate diagnosis. Many patients remain underdiagnosed or misdiagnosed consequently affecting their prognosis and quality of life. Therefore, we aimed to establish clinical and molecular characteristics of patients with increased CPK levels and muscular dystrophies in our region to facilitate diagnosis and follow-up on patients with suspected muscular dystrophies. Methods A cross-sectional study was made using a retrospective search of patients attended in Comfamiliar Risaralda between 2010 and 2021. The study included patients from both genders and all ages who presented with a diagnosis of polymyositis, myoclonus, myopathy, and muscular dystrophy between 2010 and 2022 in Comfamiliar Risaralda. Patients with CPK levels lower than 500 U/L were excluded. Results A database analysis was carried out from 2010 to 2022 of 5219 patients treated in a fourth-level care institution in the Eje Cafetero region, finding 221 patients filtered by a diagnosis of myopathy, myoclonus, polymyositis, and dystrophy. We found a combined prevalence of all muscular dystrophies of 4.2 per 100.000 among patients treated in our hospital base, Duchenne muscular dystrophy of 0.6 per 100.000, limb-girdle muscular dystrophy of 0.6 per 100.000, facioscapulohumeral dystrophy of 0.5 per 100.000, Bethem dystrophy, type 2 Emery Dreifuss muscular dystrophy, merosin-deficient muscular dystrophy and myosin storage disease of 0.1 per 100.000. A diagnostic sequence was elaborated from clinical and paraclinical features found in our patients. A diagnostic sequence was elaborated from clinical and paraclinical features found in our patients. Conclusions Although muscular dystrophies consist of a heterogeneous group of neuromuscular diseases, there are still clinical and paraclinical features that can help physicians to detect any particular case and perform a good approach and follow-up. Our diagnostic sequence will facilitate physicians to determine any particular muscular dystrophy.

Diagnostic strategies for muscular dystrophies: a cross-sectional study

Background: Muscular dystrophies are a wide heterogeneity group of neuromuscular diseases that very often constitutes a challenge for clinicians to perform an adequate diagnosis. Many patients remain underdiagnosed o misdiagnosed consequently affecting their prognosis and quality of life. Therefore, we aimed to establish clinical and molecular characteristics of patients with increased CPK levels and muscular dystrophies in our region to facilitate diagnosis and follow-up on patients with suspected muscular dystrophies. Methods: A cross-sectional study was made using a retrospective search of patients attended in Comfamiliar Risaralda between 2010 and 2021. The study included patients from both genders and all ages who presented with a diagnosis of polymyositis, myoclonus, myopathy, and muscular dystrophy between 2010 and 2022 in Comfamiliar Risaralda. Patients with CPK levels lower than 500 U/L were excluded. Results: A database analysis was carried out from 2010 to 2022 of 5219 patients treated in a fourth-level care institution in the Eje Cafetero region, finding 221 patients filtered by a diagnosis of myopathy, myoclonus, polymyositis, and dystrophy. We found a combined prevalence of all muscular dystrophies of 4.2 per 100.000 habitants, Duchenne muscular dystrophy of 0.6 per 100.000 habitants, limb-girdle muscular dystrophy of 0.6 per 100.000 habitants, facioscapulohumeral dystrophy of 0.5 per 100.000 habitants, Bethem dystrophy, type 2 Emery Dreifuss muscular dystrophy and merosin-deficient muscular dystrophy of 0.1 per 100.000 habitants. A diagnostic sequence was elaborated from clinical and paraclinical features found in our patients. Conclusions: Although muscular dystrophies consist of a heterogeneous group of neuromuscular diseases, there are still clinical and paraclinical features that can help physicians to detect any particular case and perform a good approach and follow-up. Our diagnostic sequence will facilitate physicians to determine any particular muscular dystrophy.

Merosin-deficient muscular dystrophy: pathogenesis, clinical manifestations and therapeutic strategies

Merosin-deficient muscular dystrophy is the most common form of congenital muscular dystrophies (СMD), characterized by genetic heterogeneity and a severe course in most cases. CMD pathogenesis is associated with a partial or complete absence of laminin 2 chains in the basal membrane of muscle fiber caused by a mutation in theLAMA2gene. The clinical manifestations of LAMA2-associated muscular dystrophy vary from severe СMD (СMD 1A) with an early onset to a relatively mild course with a late onset and phenotype of limb-girdle muscular dystrophy. CMD type 1A is characterized by a delay in motor development from the first months of the life (while the vast majority of children do not master the ability to walk independently), facial muscles weakness, ptosis, ophthalmoplegia, spine rigidity, early occurrence of contractures in the shoulder, elbow, hip and knee joints, restrictive respiratory disorders, nutritional problems, such as disorders of swallowing and chewing, gastroesophageal reflux, low body weight; some children suffer from mental retardation and epilepsy.

Impact of scoliosis surgery on pulmonary function in patients with muscular dystrophies and spinal muscular atrophy.

Scoliosis is a common complication of severe neuromuscular diseases. The aim of this study is to determine the impact of posterior spinal fusion on pulmonary function parameters in patients with severe neuromuscular disease at our medical center. Retrospective chart review of all patients with severe neuromuscular disease who had posterior spinal fusion between 2012 and 2017 at Texas Children's Hospital. Patients with growing rods, brain injury or malformation, and/or spina bifida were excluded. Pulmonary function measures before and after spinal surgery were determined. A total of 20 eligible patients were identified, 7 with Duchenne muscular dystrophy, 6 with spinal muscular atrophy, 3 with merosin deficient muscular dystrophy, 2 with Charcot-Marie-Tooth, 1 with central core disease, and 1 with dystroglycanopathy. The mean change in vital capacity from pre- to postspine surgery was a loss of 0.63 L for the spinal muscular atrophy patients, a loss of 0.36 L for the Duchenne muscular dystrophy patients, and a gain of 0.23 L for the merosin deficient patients. The difference between spinal muscular atrophy and merosin deficient patients was statistically significant (P = .02) CONCLUSION: In this single-center retrospective study, we found that after spine surgery for scoliosis, all patients with spinal muscular atrophy and most patients with Duchenne muscular dystrophy lost vital capacity, while the patients with merosin deficient muscular dystrophy gained vital capacity. These differences were not associated with differences is respiratory strength, body mass index, or surgical outcomes.

40. SIMULTANEOUS PREIMPLANTATION GENETIC TESTING (PGT) FOR 5 DIFFERENT GENETIC CONDITIONS

Introduction It is a common practice to perform PGT-M for one or two disorders at the same test, but it is the first PGT performed simultaneously for 5 different conditions, which is presented below. Material and Methods Consanguineous couple presented for PGT-M to avoid the risk of producing another affected child homozygous for four different autosomal recessive conditions identified in their previous offspring, including: (1) early infantile epileptic encephalopathy 5 (EIEE5), caused by SPTAN1 mutation; (2) xeroderma pigmentosum-complementation group C (XPG), caused by ERCC5 mutation; (3) congenital merosin–deficient muscular dystrophy 1A (MDC1A), caused by LAMA2 mutation; and (4) phenylketonuria (PKU) caused by PAH mutation. As parents requested also aneuploiidy testing, PGT design was to combine PGT-A and PGT-M, involving mutation and linked marker testing by multiplex nested PCR, to avoid the undetected ADO of each of the genes tested. Results Overall, 12 of 16 embryos reaching the blatocyst stage were tested together with NGS for PGT-A, of which 10 were affected, including 6 affected by one mutation, and four by two mutations. Only 2 embryos were unaffected carriers of all 4 gene mutations, of which one was with trisomy 13, so only a single embryos euploid and carrier of all 4 gene mutations was transferred, resulting, resulting in birth of a healthy unaffected baby. Although a cumulative risk of couple for producing an offspring affected by all the four conditions is only 0.4%, the couple still has been very unfortunate to produce such a child in their natural cycle. Although the chance for detecting unaffected embryo was also not high enough (31.6%), especially by added 50% risk for aneuploidy (15.8%), still one of 12 embryos tested was both euploid and normal carrier of all the mutations, resulting in a healthy, unaffected child. Conclusions This is the world's first PGT for 5 different genetic conditions (EIEE5, XPG, MDC1A, PKU and aneuploidy) in a single test, resulting in a transfer of euploid embryo free of all the conditions tested, demonstrating feasibility and accuracy of simultaneous combined PGT for multiple genetic conditions.

Clinical and molecular-genetic profiles of patients with morphological indications of congenital multicore myopathy

Congenital core myopathies are a clinically and genetically heterogenous group of congenital myopathies that share a specific histopathological feature: areas of reduced oxidative activity in muscle fibers. The relationship between clinical, genetic and morphological characteristics of this group of disorders remains understudied. The aim of this work was to compare clinical presentations and morphological phenotypes of patients with congenital myopathies/myodystrophy to the data yielded by massively parallel exome sequencing. Eight children were included in the study: 2 boys and 6 girls aged 3 to 14 years. Their biopsy material was analyzed by light and electron microscopy. Sequencing was performed on HiSeq2500. Mutations were detected in 7 (87.5%) of 8 participants. Six children had 8 mutations in the genes associated with congenital core myopathies; one patient had 2 mutations in the LAMA2 gene implicated in merosin-deficient muscular dystrophy. The proportions of patients with mutations in RYR1 and SEPN1 were equal (42.86%). Of 10 detected mutations, 3 had not been previously described, including c.7561G>A in RYR1, c.485C>A in SEPN1 and p.Cys1136Arg in LAMA2. The clinical and morphological features of core myopathies suggest that genetic causes of this group of disorders should not be limited to RYR1 and SEPN1 genes only. This necessitates the search for and the study of other genes implicated in congenital myopathies or myodystrophy using state-of-the-art molecular genetic tools.

Congenital muscular dystrophy, cardiomyopathy, and peripheral neuropathy due to merosin deficiency: Peripheral nerve histology of cauda equina

Peripheral neuropathy, white matter abnormalities, and cardiomyopathy are associated findings with merosin-deficient congenital muscular dystrophy. Although characterization of the neuropathy with nerve conduction studies has been well documented, limited research has been able to correlate histopathology with nerve biopsy in humans. Our understanding of the mechanism, described as a demyelinating neuropathy, is mainly derived from mouse model studies. We report a 23-year-old male who succumbed to respiratory failure and ultimately cardiac arrhythmia in the setting of an uncharacterized end stage progressive muscular disease complicated by cardiomyopathy and severe scoliosis. Autopsy revealed extensive muscular atrophy and replacement by fibroadipose tissue throughout the skeletal muscle and myocardium. Immunohistochemical analysis of the muscle biopsy showed a complete loss of merosin. Thus, the cause for both his muscular disease and demyelinating neuropathy was established with the diagnosis of merosin-deficient muscular dystrophy. Nerve biopsy obtained from the cauda equina showed clear evidence of segmental demyelination and remyelination, providing a better understanding of the proximal peripheral nerve histopathological changes in this disease entity.

G.P.29: Implementing robustness of preclinical efficacy studies: Need for a concerted effort

In the last few years, several publications, editorials and commentaries have addressed the issue of transparency and reproducibility in research. When research is conducted on animal models with the aim of assessing the potential efficacy of a treatment for patients, the robustness of results becomes even more important, as data may serve as the scientific rationale for large, expensive and ultimately unsuccessful clinical trials. Surely, the response of animal models to drugs and treatments may not precisely reflect the response observed in patients. However, there is overwhelming evidence that animal models are very valuable for the understanding of disease pathogenesis, and for developing therapeutic interventions, provided that experiments are carefully designed, interpreted and reported. Therefore, the transparency, reproducibility and finally also the predictive power of preclinical experiments can be significantly improved by adopting general standards in experimental design. The TREAT-NMD Network recognized this need in the scientific community years ago and initiated the implementation of standard operating protocols for the most common animal models of neuromuscular diseases. With the collaboration of several key scientists, a number of protocols was drafted and made available to the community. Today, the Swiss Foundation for Research on Muscle Diseases, a member of the TREAT-NMD Alliance, took over the regular reviewing of the protocols and the expansion to other disease areas. In the last two years, with the support of CureCMD and AFM, several protocols for mouse models of merosin-deficient muscular dystrophy were finalized and published online. Besides common experimental protocols, however, a discussion with main stakeholders will be needed as to which guidelines in reporting preclinical efficacy data need to be implemented to significantly improve the predictive power of preclinical research for patient trials.

Successful use of BPL Factor X concentrate in a child with severe factor X deficiency

Abstract Introduction: Severe factor X deficiency is a rare serious bleeding disorder historically treated with fresh frozen plasma (FFP) and more recently with prothrombin complex concentrate (PCC) which contains activated factors II, VII, IX and X. The infusion volume of PCC is smaller than FFP, but there is a risk of thromboembolic complications given the presence of activated forms of vitamin K-dependent factor concentrates when treating an isolated coagulation factor deficiency. Methods: We describe the case of a nine-year-old girl of consanguineous origin with co-existent congenital merosin deficient muscular dystrophy and severe factor X deficiency treated with twice-weekly PCC prophylaxis via an indwelling central venous access device (CVAD). Infusion occlusion of her fifth CVAD occurred 24-months post-insertion; thrombus within the right subclavian and brachiocephalic veins was seen on radiological imaging. She started peripheral treatment with BPL Factor X concentrate as infusion volumes were smaller and given her immobility further thrombotic risk was predicted to be reduced. A sixth CVAD was inserted seven months later and BPL Factor X prophylaxis was continued. Results:BPL Factor X concentrate was effective in maintaining trough levels of 13IU/ml 72-hours post-dose, with no intercurrent bleeding episodes or further problems in terms of occlusion of her portacath. Further radiological screening has not been undertaken. Conclusion: BPL Factor X has been shown to be a safe and effective alternative to PCC for treatment of severe factor X deficiency in this case.

Alternative splicing dysregulation secondary to skeletal muscle regeneration

Dysregulation of alternative splicing has become a molecular hallmark of myotonic dystrophy type 1 (DM1), in which neonatal splice variants are expressed in adult skeletal muscle. Splicing dysregulation is induced by RNA containing expanded CUG repeats expressed from the expanded mutant allele by sequestration of muscleblindlike 1 (MBNL1) protein within nuclear RNA foci and increased CUGBP, ELAV-like family member 1 (CELF1) protein levels. Dysregulated splicing has also been identified in other neuromuscular disorders, suggesting either that diseases with different molecular causes share a common pathogenic mechanism or that dysregulated splicing can also be a common secondary consequence of muscle degeneration and regeneration. In this study, we examined regulation of alternative splicing in 4 different mouse models of muscular dystrophy, including DM1, limb-girdle muscular dystrophy, congenital merosin-deficient muscular dystrophy, and Duchenne muscular dystrophy, and 2 myotoxin (cardiotoxin and notexin) muscle injury models. We show that DM1-like alternative splicing dysregulation and altered expression of MBNL1 and CELF1 occur in non-DM1 mouse models of muscular dystrophy and muscle injury, most likely due to recapitulation of neonatal splicing patterns in regenerating fibers. In contrast, CELF1 was elevated in nuclei of mature myofibers of the DM1 model, consistent with a primary effect of pathogenic RNA expression. Splicing dysregulation in DM1 is a primary effect of RNA containing expanded CUG repeats. However, we conclude that splicing changes can also be observed secondary to muscle regeneration, and this possibility must be taken into account when evaluating cause-effect relationships between dysregulated splicing and disease processes.

P22 Clinical and pathological heterogeneity in partial merosin deficiency

P22 Clinical and pathological heterogeneity in partial merosin deficiency

Extraocular muscle in merosin-deficient muscular dystrophy: cation homeostasis is maintained but is not mechanistic in muscle sparing.

Extraocular muscle is uniquely spared from damage in merosin-deficient congenital muscular dystrophy. Using a murine model, we have tested the hypothesis that the maintenance of calcium homeostasis is mechanistic in extraocular muscle protection. Atomic absorption spectroscopy has demonstrated a strong correlation between the perturbation of calcium homeostasis in hindlimb muscle that is severely damaged and the absence of changes in calcium in extraocular muscle. If, as in other skeletal muscles, extraocular muscle fibers are destabilized by merosin deficiency, we would expect an increase in total muscle calcium coupled with an adaptive response in the high capacity/speed of the sarcoplasmic reticulum of the eye muscle. However, we have not observed the expected increases in total muscle calcium content, Ca2+-ATPase activity, Na+/Ca2+ exchanger content, or smooth ER Ca2+-ATPase content that are predicted by this model. Instead, these results indicate that the increased membrane permeability that characterizes, and is potentially mechanistic in, myofiber degeneration in muscular dystrophy does not occur in merosin-deficient extraocular muscle. Thus, the high-capacity calcium-scavenging systems are not primarily responsible for extraocular muscle protection in muscular dystrophy.

Disruption of thelama2Gene in Embryonic Stem Cells: Laminin α2 Is Necessary for Sustenance of Mature Muscle Cells

Mutations in the gene coding for the α2 chain of laminin-2 and -4 (merosin) cause a severe form of congenital muscular dystrophy in humans and mice. To establish a defined model forin vitroandin vivostudies of the role of laminin α2/merosin in development and cell and tissue function, we generated several lines of mutant embryonic stem (ES) cell with disruption of the laminin α2 chain gene. We find that homozygous mutant ES cells differentiate normallyin vitro,giving rise to cardiomyocytes, myotubes, and smooth muscle cells in addition to many other cell types. However, the myotubes that are formed are unstable. They detach, collapse, and degenerate, a process which is initiated at the appearance of the mature, contractile phenotype of the cells. We propose that the detachment and death of contracting myotubesin vitrohas its counterpartin vivoand that contraction-induced myofiber damage, along with the lack of survival cues provided by laminin α2/merosin, is a significant contribution to muscle degeneration in merosin-deficient muscular dystrophy.