A healthcare claims analysis to identify and characterize patients with suspected X-Linked Myotubular Myopathy (XLMTM) in the Brazilian Healthcare System.

BACKGROUND: X-linked myotubular myopathy (XLMTM) is a rare, life-threatening congenital disease, which is not well-defined. To our knowledge, no studies characterizing the XLMTM disease burden have been conducted in Brazil. We identified and described patients with suspected XLMTM using administrative claims data from the Brazilian public healthcare system. METHODS: Data from 2015 to 2019 were extracted from the DATASUS database. As no XLMTM-specific ICD-10 code was available, a stepwise algorithm was applied to identify patients with suspected XLMTM by selecting male patients with a congenital myopathies code (G71.2), aged < 18 years at index date (first claim of G71.2), with an associated diagnostic procedure (muscle biopsy/genetic test) and without spinal muscular atrophy or Duchenne muscular dystrophy. We attempted to identify patients with suspected severe XLMTM based on use of both respiratory and feeding support, which are nearly universal in the care of XLMTM patients. Analyses were performed for the overall cohort and stratified by age at index date < 5 years old and ≥ 5 years old. RESULTS: Of 173 patients with suspected XLMTM identified, 39% were < 5 years old at index date. Nearly all (N = 166) patients (96%) were diagnosed by muscle biopsy (91% of patients < 5 years old and 99% of patients ≥ 5 years old), six (3.5%) were diagnosed by clinical evaluation (8% of patients < 5 years old and 1% of patients ≥ 5 years old), and one was diagnosed by a genetic test. Most patients lived in Brasilia (n = 55), São Paulo (n = 33) and Minas Gerais (n = 27). More than 85% of patients < 5 years old and approximately 75% of patients ≥ 5 years old had physiotherapy at the index date. In both age groups, nearly 50% of patients required hospitalization at some point and 25% required mobility support. Respiratory and feeding support were required for 3% and 12% of patients, respectively, suggesting that between 5 and 21 patients may have had severe XLMTM. CONCLUSION: In this real-world study, genetic testing for XLMTM appears to be underutilized in Brazil and may contribute to underdiagnosis of the disease. Access to diagnosis and care is limited outside of specific regions with specialized clinics and hospitals. Substantial use of healthcare resources included hospitalization, physiotherapy, mobility support, and, to a lesser extent, feeding support and respiratory support.

Marked neuropsychiatric involvement and dysmorphic features in nemaline myopathy.

BACKGROUND: Inherited nemaline myopathy is one of the most common congenital myopathies. This genetically heterogeneous disease is defined by the presence of nemaline bodies in muscle biopsy. The phenotypic spectrum is wide and cognitive involvement has been reported, although not extensively evaluated. METHODS: We report two nemaline myopathy patients presenting pronounced central nervous system involvement leading to functional compromise and novel facial and skeletal dysmorphic findings, possibly expanding the disease phenotype. RESULTS: One patient had two likely pathogenic NEB variants, c.2943G > A and c.8889 + 1G > A, and presented cognitive impairment and dysmorphic features, and the other had one pathogenic variant in ACTA1, c.169G > C (p.Gly57Arg), presenting autism spectrum disorder and corpus callosum atrophy. Both patients had severe cognitive involvement despite milder motor dysfunction. CONCLUSION: We raise the need for further studies regarding the role of thin filament proteins in the central nervous system and for a systematic cognitive assessment of congenital myopathy patients.

Bailey-Bloch Congenital Myopathy in Brazilian Patients: A Very Rare Myopathy with Malignant Hyperthermia Susceptibility.

BACKGROUND: Congenital myopathy-13 (CMYP13), also known as Bailey-Bloch congenital myopathy and Native American myopathy (NAM), is a condition caused by biallelic missense pathogenic variants in STAC3, which encodes an important protein necessary for the excitation-relaxation coupling machinery in the muscle. Patients with biallelic pathogenic variants in STAC3 often present with congenital weakness and arthrogryposis, cleft palate, ptosis, myopathic facies, short stature, kyphoscoliosis, and susceptibility to malignant hyperthermia provoked by anesthesia. We present two unrelated cases of Bailey-Bloch congenital myopathy descendants of non-consanguineous parents, which were investigated for delayed psychomotor development and generalized weakness. To the best of our knowledge, these are the first descriptions of CMYP13 in Brazil. In both patients, we found the previously described pathogenic missense variant p.Trp284Ser in homozygosity. CONCLUSION: We seek to highlight the need for screening for CMYP13 in patients expressing the typical phenotype of the disease even in the absence of Lumbee Native American ancestry, and to raise awareness to possible complications like malignant hyperthermia in Bailey-Bloch congenital myopathy.

A Possible Case of Centronuclear Myopathy: A Case Report.

Congenital myopathies (CMs) are a group of diseases that primarily affect the muscle fiber, especially the contractile apparatus and the different components that condition its normal functioning. They present as muscle weakness and hypotonia at birth or during the first year of life. Centronuclear CM is characterized by a high incidence of nuclei located centrally and internally in muscle fibers. Clinical case: a 22-year-old male patient with symptoms of muscle weakness since early childhood, with difficulty in performing physical activity according to his age, with the presence of a long face, a waddling gait, and a global decrease in muscle mass. Electromyography was performed, showing a neurogenic pattern and not the expected myopathic one, neuroconduction with reduced amplitude of the motor potential of the peroneal nerve and axonal and myelin damage of the posterior tibial nerves. The microscopic study of the studied striated muscle fragments stained with hematoxylin-eosin and Masson's trichrome showed the presence of fibers with central nuclei, diagnosing CM. The patient meets most of the description for CM, with involvement of all striated muscles, although it is important to note the neurogenic pattern present in this case, due to the denervation of damaged muscle fibers, which contain terminal axonal segments. Neuroconduction shows the involvement of motor nerves, but with normal sensory studies, axonal polyneuropathy is unlikely, due to normal sensory potentials. Different pathological findings have been described depending on the mutated gene in this disease, but all coincide with the presence of fibers with central nuclei for diagnosis by this means, which is so important in institutions where it is not possible to carry out genetic studies, and allowing early specific treatment, according to the stage through which the patient passes.

Nemaline Myopathy in Brazilian Patients: Molecular and Clinical Characterization.

Nemaline myopathy (NM), a structural congenital myopathy, presents a significant clinical and genetic heterogeneity. Here, we compiled molecular and clinical data of 30 Brazilian patients from 25 unrelated families. Next-generation sequencing was able to genetically classify all patients: sixteen families (64%) with mutation in NEB, five (20%) in ACTA1, two (8%) in KLHL40, and one in TPM2 (4%) and TPM3 (4%). In the NEB-related families, 25 different variants, 11 of them novel, were identified; splice site (10/25) and frame shift (9/25) mutations were the most common. Mutation c.24579 G>C was recurrent in three unrelated patients from the same region, suggesting a common ancestor. Clinically, the "typical" form was the more frequent and caused by mutations in the different NM genes. Phenotypic heterogeneity was observed among patients with mutations in the same gene. Respiratory involvement was very common and often out of proportion with limb weakness. Muscle MRI patterns showed variability within the forms and genes, which was related to the severity of the weakness. Considering the high frequency of NEB mutations and the complexity of this gene, NGS tools should be combined with CNV identification, especially in patients with a likely non-identified second mutation.

A Novel SPEG mutation causing congenital myopathy with fiber size disproportion and dilated cardiomyopathy with heart transplantation.

Congenital myopathies are a heterogeneous group of conditions diagnosed based on the clinical presentation, muscle histopathology and genetic defects. Recessive mutations in the SPEG gene have been described in recent years and are primarily associated with centronuclear myopathy with cardiomyopathy. In this report, we describe two Brazilian siblings, aged 13 and 6 years, with a novel homozygous mutation (c.8872 C>T:p.Arg2958Ter) in the SPEG gene leading to a congenital myopathy. In the older sibling, the muscle biopsy showed fiber size disproportion. The mean diameter of type 2 fibers (119 µm) was significantly higher than type 1 (57 µm) (P < 0,001) with a 72% prevalence of type 1 fibers. The patient also had progressive cardiomyopathy treated with heart transplantation. The present report expands the muscle histopathological findings related to mutations in the SPEG gene, including fiber size disproportion without central nuclei. Additionally, this report describes the first case of heart transplantation in a patient with SPEG mutations.

[Diagnosis and treatment of congenital myopaties]. / Diagnóstico y tratamiento de las miopatías congénitas.

Important advances have been made in the field of congenital myopathies in recent years, forcing clinicians to constantly review and update this group of diseases. The increasing identification of new genes and phenotypes associated with already known genes has been possible to a great extent thanks to the development accomplished in next generation sequencing techniques, which are increasingly accessible. Knowing better the phenotypic spectrum of these entities allows to establish a phenotype/genotype correlation in some subgroups. The best understanding of the pathophysiology and natural history of these diseases are fundamental to design new therapies. The first clinical trials in the field of gene therapy are already a reality and are showing positive results, creating a new expectation for patients, families and specialists, which will be reflected in the need to adapt the protocols of care, diagnosis and treatment of some of these entities. It is essential that pediatric neurologists, pediatricians, physiotherapists and other professionals involved in the care of these patients are informed and updated on the advances in this group of diseases.

Existen importantes avances en el campo de las miopatías congénitas en los últimos años que obligan a la revisión y actualización constante de este grupo de enfermedades. La identificación creciente de nuevos genes y fenotipos asociados a genes ya conocidos, fue posible en gran medida gracias al avance de las técnicas de secuenciación de nueva generación, cada vez más accesibles. El conocer mejor el espectro fenotípico de estas entidades, permite establecer una correlación fenotipo/genotipo en algunos subgrupos. La mejor compresión de la fisiopatología e historia natural de estas enfermedades, son fundamentales para el desarrollo de nuevas terapias. Los primeros ensayos clínicos en el campo de la terapia génica ya son una realidad y están mostrando resultados positivos, creando una nueva expectativa en paciente, familiares y especialistas, lo que se verá reflejado en la necesidad de adaptar los protocolos de atención, diagnóstico y tratamiento de algunas de estas entidades. Es fundamental que los neuropediatras, pediatras, fisioterapeutas y otros profesionales involucrados en el cuidado de estos pacientes, estén informados y actualizados de los avances en este grupo de enfermedades.

Diagnóstico y tratamiento de las miopatías congénitas / Diagnosis and treatment of congenital myopaties

Existen importantes avances en el campo de las miopatías congénitas en los últimos años que obligan a la revisión y actualización constante de este grupo de enfermedades. La identificación creciente de nuevos genes y fenotipos asociados a genes ya conocidos, fue posible en gran medida gracias al avance de las técnicas de secuenciación de nueva generación, cada vez más accesibles. El conocer mejor el espectro fenotípico de estas entidades, permite establecer una correlación fenotipo/genotipo en algunos subgrupos. La mejor compresión de la fisiopatología e historia natural de estas enfermedades, son fundamentales para el desarrollo de nuevas terapias. Los primeros ensayos clínicos en el campo de la terapia génica ya son una realidad y están mostrando resultados positivos, creando una nueva expectativa en paciente, familiares y especialistas, lo que se verá reflejado en la necesidad de adaptar los protocolos de atención, diagnóstico y tratamiento de algunas de estas entidades. Es fundamental que los neuropediatras, pediatras, fisioterapeutas y otros profesionales involucrados en el cuidado de estos pacientes, estén informados y actualizados de los avances en este grupo de enfermedades.

Important advances have been made in the field of congenital myopathies in recent years, forcing clinicians to constantly review and update this group of diseases. The increasing identification of new genes and phenotypes associated with already known genes has been possible to a great extent thanks to the development accomplished in next generation sequencing techniques, which are increasingly accessible. Knowing better the phenotypic spectrum of these entities allows to establish a phenotype/genotype correlation in some subgroups. The best understanding of the pathophysiology and natural history of these diseases are fundamental to design new therapies. The first clinical trials in the field of gene therapy are already a reality and are showing positive results, creating a new expectation for patients, families and specialists, which will be reflected in the need to adapt the protocols of care, diagnosis and treatment of some of these entities. It is essential that pediatric neurologists, pediatricians, physiotherapists and other professionals involved in the care of these patients are informed and updated on the advances in this group of diseases.

Clinical and Histologic Findings in ACTA1-Related Nemaline Myopathy: Case Series and Review of the Literature.

BACKGROUND: Nemaline myopathy is a rare congenital disease of skeletal muscle characterized by muscle weakness and hypotonia, as well as the diagnostic presence of nemaline rods in skeletal muscle fibers. Nemaline myopathy is genetically and phenotypically heterogeneous and, so far, mutations in 11 different genes have been associated with this disease. Dominant mutations in ACTA1 are the second most frequent genetic cause of nemaline myopathy and can lead to a variety of clinical and histologic phenotypes. PATIENTS AND METHODS: We present a series of ACTA1-related cases from a Brazilian cohort of 23 patients with nemaline myopathy, diagnosed after Sanger sequencing the entire coding region of ACTA1, and review the literature on ACTA1-related nemaline myopathy. RESULTS: The study confirmed ACTA1 mutations in four patients, including one with intranuclear rods, one with large intracytoplasmic aggregates, and two with nemaline intracytoplasmic rods. A repeat muscle biopsy in one patient did not show histological progression. CONCLUSION: Despite the recognized phenotypic variability in ACTA1-related nemaline myopathy, clinical and histological presentations appear to correlate with the position of the mutation, which confirms emerging genotype/phenotype correlations and better predict the prognosis of affected patients.

A Study of a Cohort of X-Linked Myotubular Myopathy at the Clinical, Histologic, and Genetic Levels.

BACKGROUND: Myotubular myopathy is a rare X-linked congenital myopathy characterized by marked neonatal hypotonia and respiratory insufficiency, facial and ocular involvement, and muscle biopsy with prominent central nuclei in the majority of muscle fibers. It is caused by mutations in MTM1, which codes for the phosphoinositides phosphatase myotubularin. In this work, we established and detailed a new cohort of six patients at the clinical, histologic, and genetic levels. PATIENTS AND METHODS: Patients were recruited after screening 3065 muscle biopsy reports from two large biopsy banks in Sao Paulo, Brazil from the years 2008 to 2013, and from referrals to a neuromuscular outpatient clinic between 2011 and 2013. We reviewed biopsy slides, evaluated patients, and Sanger sequenced MTM1 in the families. RESULTS: All patients but one had classic phenotypes with a stable course after a severe onset. Two patients died suddenly from hypovolemic shock. Muscle biopsies had been performed in five patients, all of whom showed a classic pattern with a predominance of centrally located nuclei and increased oxidative activity in the center of the fibers. Two patients showed necklace fibers, and two families had novel truncating mutations in MTM1. CONCLUSIONS: X-linked myotubular myopathy is rare in the Brazilian population. Necklace fibers might be more prevalent in this condition than previously reported. Direct Sanger sequencing of MTM1 on clinical suspicion avoids the need of a muscle biopsy.

DNM2 mutations in a cohort of sporadic patients with centronuclear myopathy.

Centronuclear myopathy (CNM) is a rare congenital muscle disease characterized by fibers with prominent centralized nuclei in muscle biopsies. The disease is clinically heterogeneous, ranging from severe neonatal hypotonic phenotypes to adult-onset mild muscle weakness, and can have multiple modes of inheritance in association with various genes, including MTM1, DNM2, BIN1 and RYR1. Here we analyzed 18 sporadic patients with clinical and histological diagnosis of CNM and sequenced the DNM2 gene, which codes for the dynamin 2 protein. We found DNM2 missense mutations in two patients, both in exon 8, one known (p.E368K) and one novel (p.F372C), which is found in a position of presumed pathogenicity and appeared de novo. The patients had similar phenotypes characterized by neonatal signs followed by improvement and late childhood reemergence of slowly progressive generalized muscle weakness, elongated face with ptosis and ophthalmoparesis, and histology showing fibers with radiating sarcoplasmic strands (RSS). These patients were the only ones in the series to present this histological marker, which together with previous reports in the literature suggest that, when RSS are present, direct sequencing of DNM2 mutation hot spot regions should be the first step in the molecular diagnosis of CNM, even in sporadic cases.

Muscle magnetic resonance imaging and histopathology in ACTA1-related congenital nemaline myopathy.

INTRODUCTION: Muscle biopsy is usually diagnostic in nemaline myopathy (NM), but some patients may show nonspecific findings, leading to pitfalls in diagnosis. Muscle MRI is a helpful complementary tool. METHODS: We assessed the clinical, histopathological, MRI, and molecular findings in a 19-year-old patient with NM in whom 2 muscle biopsies with ultrastructural examination showed no nemaline bodies. We analyzed the degree and pattern of muscle MRI involvement of the entire body, including the tongue and pectoral muscles. RESULTS: Muscle MRI abnormalities in sartorius, adductor magnus, and anterior compartment muscles of the leg suggested NM. A previously unreported fatty infiltration of the tongue was found. A third biopsy after the muscle MRI showed scant nemaline bodies. A novel heterozygous de novo ACTA1 c.611C>T/p.Thr204Ile mutation was detected. CONCLUSIONS: We highlight the contribution of muscle imaging in addressing the genetic diagnosis of ACTA1-related NM.