Consensus from the Brazilian Academy of Neurology for the diagnosis, genetic counseling, and use of disease-modifying therapies in 5q spinal muscular atrophy.

Spinal muscular atrophy linked to chromosome 5 (SMA-5q) is an autosomal recessive genetic disease caused by mutations in the SMN1. SMA-5q is characterized by progressive degeneration of the spinal cord and bulbar motor neurons, causing severe motor and respiratory impairment with reduced survival, especially in its more severe clinical forms. In recent years, highly effective disease-modifying therapies have emerged, either acting by regulating the splicing of exon 7 of the SMN2 gene or adding a copy of the SMN1 gene through gene therapy, providing a drastic change in the natural history of the disease. In this way, developing therapeutic guides and expert consensus becomes essential to direct the use of these therapies in clinical practice. This consensus, prepared by Brazilian experts, aimed to review the main available disease-modifying therapies, critically analyze the results of clinical studies, and provide recommendations for their use in clinical practice for patients with SMA-5q. This consensus also addresses aspects related to diagnosis, genetic counseling, and follow-up of patients under drug treatment. Thus, this consensus provides valuable information regarding the current management of SMA-5q, helping therapeutic decisions in clinical practice and promoting additional gains in outcomes.

Atrofia muscular espinhal ligada ao cromossomo 5 (AME-5q) é uma doença genética de herança autossômica recessiva causada por mutações no gene SMN1. A AME-5q cursa com degeneração progressiva dos motoneurônios medulares e bulbares, acarretando grave comprometimento motor e respiratório com redução da sobrevida, especialmente nas suas formas clínicas mais graves. Nos últimos anos, terapias modificadoras da doença altamente eficazes, ou que atuam regulando o splicing do exon 7 do gene SMN2 ou adicionando uma cópia do gene SMN1 via terapia gênica, têm surgido, proporcionando uma mudança drástica na história natural da doença. Dessa forma, o desenvolvimento de guias terapêuticos e de consensos de especialistas torna-se importante no sentido de direcionar o uso dessas terapias na prática clínica. Este consenso, preparado por especialistas brasileiros, teve como objetivos revisar as principais terapias modificadoras de doença disponíveis, analisar criticamente os resultados dos estudos clínicos dessas terapias e prover recomendações para seu uso na prática clínica para pacientes com AME-5q. Aspectos relativos ao diagnóstico, aconselhamento genético e seguimento dos pacientes em uso das terapias também são abordados nesse consenso. Assim, esse consenso promove valiosas informações a respeito do manejo atual da AME-5q auxiliando decisões terapêuticas na prática clínica e promovendo ganhos adicionais nos desfechos finais.

Consensus from the Brazilian Academy of Neurology for the diagnosis, genetic counseling, and use of disease-modifying therapies in 5q spinal muscular atrophy / Consenso da Academia Brasileira de Neurologia para diagnóstico, aconselhamento genético e uso de terapias modificadoras na atrofia muscular espinhal 5q

Abstract Spinal muscular atrophy linked to chromosome 5 (SMA-5q) is an autosomal recessive genetic disease caused by mutations in the SMN1. SMA-5q is characterized by progressive degeneration of the spinal cord and bulbar motor neurons, causing severe motor and respiratory impairment with reduced survival, especially in its more severe clinical forms. In recent years, highly effective disease-modifying therapies have emerged, either acting by regulating the splicing of exon 7 of the SMN2 gene or adding a copy of the SMN1 gene through gene therapy, providing a drastic change in the natural history of the disease. In this way, developing therapeutic guides and expert consensus becomes essential to direct the use of these therapies in clinical practice. This consensus, prepared by Brazilian experts, aimed to review the main available disease-modifying therapies, critically analyze the results of clinical studies, and provide recommendations for their use in clinical practice for patients with SMA-5q. This consensus also addresses aspects related to diagnosis, genetic counseling, and follow-up of patients under drug treatment. Thus, this consensus provides valuable information regarding the current management of SMA-5q, helping therapeutic decisions in clinical practice and promoting additional gains in outcomes.

Resumo Atrofia muscular espinhal ligada ao cromossomo 5 (AME-5q) é uma doença genética de herança autossômica recessiva causada por mutações no gene SMN1. A AME-5q cursa com degeneração progressiva dos motoneurônios medulares e bulbares, acarretando grave comprometimento motor e respiratório com redução da sobrevida, especialmente nas suas formas clínicas mais graves. Nos últimos anos, terapias modificadoras da doença altamente eficazes, ou que atuam regulando o splicing do exon 7 do gene SMN2 ou adicionando uma cópia do gene SMN1 via terapia gênica, têm surgido, proporcionando uma mudança drástica na história natural da doença. Dessa forma, o desenvolvimento de guias terapêuticos e de consensos de especialistas torna-se importante no sentido de direcionar o uso dessas terapias na prática clínica. Este consenso, preparado por especialistas brasileiros, teve como objetivos revisar as principais terapias modificadoras de doença disponíveis, analisar criticamente os resultados dos estudos clínicos dessas terapias e prover recomendações para seu uso na prática clínica para pacientes com AME-5q. Aspectos relativos ao diagnóstico, aconselhamento genético e seguimento dos pacientes em uso das terapias também são abordados nesse consenso. Assim, esse consenso promove valiosas informações a respeito do manejo atual da AME-5q auxiliando decisões terapêuticas na prática clínica e promovendo ganhos adicionais nos desfechos finais.

DEVOTE Study Exploring Higher Dose of Nusinersen in Spinal Muscular Atrophy: Study Design and Part A Results.

BACKGROUND: Pharmacokinetic/pharmacodynamic modeling indicates that the higher dose of nusinersen may be associated with a clinically meaningful increase in efficacy above that seen with the 12-mg approved dose. OBJECTIVE: Here we describe both the design of DEVOTE (NCT04089566), a 3-part clinical study evaluating safety, tolerability, and efficacy of higher dose of nusinersen, and results from the initial Part A. METHODS: DEVOTE Part A evaluates safety and tolerability of a higher nusinersen dose; Part B assesses efficacy in a randomized, double-blind design; and Part C assesses safety and tolerability of participants transitioning from the 12-mg dose to higher doses. RESULTS: In the completed Part A of DEVOTE, all 6 enrolled participants aged 6.1-12.6 years have completed the study. Four participants experienced treatment-emergent adverse events (TEAEs), the majority of which were mild. Common TEAEs of headache, pain, chills, vomiting, and paresthesia were considered related to the lumbar puncture procedure. There were no safety concerns regarding clinical or laboratory parameters. Nusinersen levels in the cerebrospinal fluid were within the range of modeled predictions for higher dose of nusinersen. While Part A was not designed for assessing efficacy, most participants showed stabilization or improvement in motor function. Parts B and C of DEVOTE are ongoing. CONCLUSIONS: The findings from Part A of the DEVOTE study support further development of higher dose of nusinersen.

Clinical management and diagnosis of CLN2 disease: consensus of the Brazilian experts group.

Neuronal ceroid lipofuscinosis type 2 (CLN2) is a rare neurodegenerative genetic disease that affects children in early life. Its classic form is rapidly progressive, leading to death within the first 10 years. The urge for earlier diagnosis increases with the availability of enzyme replacement therapy. A panel of nine Brazilian child neurologists combined their expertise in CLN2 with evidence from the medical literature to establish a consensus to manage this disease in Brazil. They voted 92 questions including diagnosis, clinical manifestations, and treatment of the disease, considering the access to healthcare in this country. Clinicians should suspect CLN2 disease in any child, from 2 to 4 years old, with language delay and epilepsy. Even though the classic form is the most prevalent, atypical cases with different phenotypes can be found. Electroencephalogram, magnetic resonance imaging, molecular and biochemical testing are the main tools to investigate and confirm the diagnosis. However, we have limited access to molecular testing in Brazil, and rely on the support from the pharmaceutical industry. The management of CLN2 should involve a multidisciplinary team and focus on the quality of life of patients and on family support. Enzyme replacement therapy with Cerliponase α is an innovative treatment approved in Brazil since 2018; it delays functional decline and provides quality of life. Given the difficulties for the diagnosis and treatment of rare diseases in our public health system, the early diagnosis of CLN2 needs improvement as enzyme replacement therapy is available and modifies the prognosis of patients.

Lipofuscinose ceróide neuronal (CLN2) é uma doença genética neurodegenerativa rara que afeta crianças nos primeiros anos de vida. A sua forma clássica é rapidamente progressiva, levando à morte nos primeiros 10 anos. A necessidade de um diagnóstico precoce aumenta com a disponibilidade do tratamento de terapia enzimática. Um painel de nove neurologistas infantis brasileiros combinou sua experiência em CLN2 com evidências da literatura médica para estabelecer um consenso no manejo desta doença no Brasil. Eles votaram 92 questões abordando diagnóstico, manifestações clínicas e tratamento, considerando o acesso à saúde no Brasil. Deve-se suspeitar de CLN2 em qualquer criança de 2 a 4 anos de idade que apresente atraso de linguagem e epilepsia. Apesar da forma clássica ser a mais prevalente, podem ser encontrados casos atípicos com diferentes fenótipos. Eletroencefalograma, ressonância magnética, testes moleculares e bioquímicos são as principais ferramentas para investigar e confirmar o diagnóstico. No entanto, o acesso aos testes moleculares é limitado no Brasil, necessitando contar com o apoio da indústria farmacêutica. O manejo da CLN2 deve envolver uma equipe multidisciplinar e focar na qualidade de vida dos pacientes e no apoio familiar. A terapia de reposição enzimática com Cerliponase alfa é um tratamento inovador aprovado no Brasil desde 2018; ele retarda o declínio funcional e proporciona qualidade de vida. Diante das dificuldades para o diagnóstico e tratamento de doenças raras em nosso sistema público de saúde, o diagnóstico precoce de CLN2 precisa de melhorias pois a terapia de reposição enzimática está disponível e modifica o prognóstico dos pacientes.

Update of the Brazilian consensus recommendations on Duchenne muscular dystrophy.

In the last few decades, there have been considerable improvements in the diagnosis and care of Duchenne muscular dystrophy (DMD), the most common childhood muscular dystrophy. International guidelines have been published and recently reviewed. A group of Brazilian experts has developed a standard of care based on a literature review with evidence-based graded recommendations in a two-part publication. Implementing best practice management has helped change the natural history of this chronic progressive disorder, in which the life expectancy for children of the male sex in the past used to be very limited. Since the previous publication, diagnosis, steroid treatment, rehabilitation, and systemic care have gained more significant insights with new original work in certain fields. Furthermore, the development of new drugs is ongoing, and some interventions have been approved for use in certain countries. Therefore, we have identified the need to review the previous care recommendations for Brazilian patients with DMD. Our objective was to create an evidence-based document that is an update on our previous consensus on those topics.

Nas últimas décadas, houve progressos significativos no diagnóstico e no tratamento da distrofia muscular de Duchenne (DMD), considerada a distrofia muscular mais comum na infância. Diretrizes internacionais foram publicadas e revisadas recentemente. Um grupo de especialistas brasileiros desenvolveu um padrão de atendimento baseado em revisão de literatura, com recomendações graduadas pautadas em evidências compiladas em uma publicação dividida em duas partes. A implementação de melhores práticas de manejo ajudou a modificar a história natural desta doença crônica, progressiva, que, no passado, oferecia uma expectativa de vida muito limitada para crianças do sexo masculino. Desde a publicação desse consenso anterior, o diagnóstico, o tratamento com esteroides, a reabilitação e os cuidados sistêmicos ganharam novas possibilidades a partir da divulgação dos resultados de trabalhos originais em algumas dessas áreas. Além disso, as pesquisas e o desenvolvimento de novos fármacos estão em andamento, e algumas intervenções já foram aprovadas para uso em determinados países. Nesse contexto, identificamos a necessidade de rever as recomendações anteriores sobre o manejo dos pacientes brasileiros com DMD. Nosso objetivo principal foi elaborar uma atualização baseada em evidências sobre esses tópicos do consenso.

Clinical management and diagnosis of CLN2 disease: consensus of the Brazilian experts group / Manejo clínico e diagnóstico da doença CLN2: consenso do grupo de especialistas brasileiros

Abstract Neuronal ceroid lipofuscinosis type 2 (CLN2) is a rare neurodegenerative genetic disease that affects children in early life. Its classic form is rapidly progressive, leading to death within the first 10 years. The urge for earlier diagnosis increases with the availability of enzyme replacement therapy. A panel of nine Brazilian child neurologists combined their expertise in CLN2 with evidence from the medical literature to establish a consensus to manage this disease in Brazil. They voted 92 questions including diagnosis, clinical manifestations, and treatment of the disease, considering the access to healthcare in this country. Clinicians should suspect CLN2 disease in any child, from 2 to 4 years old, with language delay and epilepsy. Even though the classic form is the most prevalent, atypical cases with different phenotypes can be found. Electroencephalogram, magnetic resonance imaging, molecular and biochemical testing are the main tools to investigateand confirm the diagnosis. However, we have limited access to molecular testing in Brazil, and rely on the support from the pharmaceutical industry. The management of CLN2 should involve a multidisciplinary team and focus on the quality of life of patients and on family support. Enzyme replacement therapy with Cerliponase α is an innovative treatment approved in Brazil since 2018; it delays functional decline and provides quality of life. Given the difficulties for the diagnosis and treatment of rare diseases in our public health system, the early diagnosis of CLN2 needs improvement as enzyme replacement therapy is available and modifies the prognosis of patients.

Resumo Lipofuscinose ceróide neuronal (CLN2) é uma doença genética neurodegenerativa rara que afeta crianças nos primeiros anos de vida. A sua forma clássica é rapidamente progressiva, levando à morte nos primeiros 10 anos. A necessidade de um diagnóstico precoce aumenta com a disponibilidade do tratamento de terapia enzimática. Um painel de nove neurologistas infantis brasileiros combinou sua experiência em CLN2 com evidências da literatura médica para estabelecer um consenso no manejo desta doença no Brasil. Eles votaram 92 questões abordando diagnóstico, manifestações clínicas e tratamento, considerando o acesso à saúde no Brasil. Deve-se suspeitar de CLN2 em qualquer criança de 2 a 4 anos de idade que apresente atraso de linguagem e epilepsia. Apesar da forma clássica ser a mais prevalente, podem ser encontrados casos atípicos com diferentes fenótipos. Eletroencefalograma, ressonância magnética, testes moleculares e bioquímicos são as principais ferramentas para investigar e confirmar o diagnóstico. No entanto, o acesso aos testes moleculares é limitado no Brasil, necessitando contar com o apoio da indústria farmacêutica. O manejo da CLN2 deve envolver uma equipe multidisciplinar e focar na qualidade de vida dos pacientes e no apoio familiar. A terapia de reposição enzimática com Cerliponase alfa é um tratamento inovador aprovado no Brasil desde 2018; ele retarda o declínio funcional e proporciona qualidade de vida. Diante das dificuldades para o diagnóstico e tratamento de doenças raras em nosso sistema público de saúde, o diagnóstico precoce de CLN2 precisa de melhorias pois a terapia de reposição enzimática está disponível e modifica o prognóstico dos pacientes.

Update of the Brazilian consensus recommendations on Duchenne muscular dystrophy / Atualização das recomendações do consenso brasileiro para distrofia muscular de Duchenne

Abstract In the last few decades, there have been considerable improvements in the diagnosis and care of Duchenne muscular dystrophy (DMD), the most common childhood muscular dystrophy. International guidelines have been published and recently reviewed. A group of Brazilian experts has developed a standard of care based on a literature review with evidence-based graded recommendations in a two-part publication. Implementing best practice management has helped change the natural history of this chronic progressive disorder, in which the life expectancy for children of the male sex in the past used to be very limited. Since the previous publication, diagnosis, steroid treatment, rehabilitation, and systemic care have gained more significant insights with new original work in certain fields. Furthermore, the development of new drugs is ongoing, and some interventions have been approved for use in certain countries. Therefore, we have identified the need to review the previous care recommendations for Brazilian patients with DMD. Our objective was to create an evidence-based document that is an update on our previous consensus on those topics.

Resumo Nas últimas décadas, houve progressos significativos no diagnóstico e no tratamento da distrofia muscular de Duchenne (DMD), considerada a distrofia muscular mais comum na infância. Diretrizes internacionais foram publicadas e revisadas recentemente. Um grupo de especialistas brasileiros desenvolveu um padrão de atendimento baseado em revisão de literatura, com recomendações graduadas pautadas em evidências compiladas em uma publicação dividida em duas partes. A implementação de melhores práticas de manejo ajudou a modificar a história natural desta doença crônica, progressiva, que, no passado, oferecia uma expectativa de vida muito limitada para crianças do sexo masculino. Desde a publicação desse consenso anterior, o diagnóstico, o tratamento com esteroides, a reabilitação e os cuidados sistêmicos ganharam novas possibilidades a partir da divulgação dos resultados de trabalhos originais em algumas dessas áreas. Além disso, as pesquisas e o desenvolvimento de novos fármacos estão em andamento, e algumas intervenções já foram aprovadas para uso em determinados países. Nesse contexto, identificamos a necessidade de rever as recomendações anteriores sobre o manejo dos pacientes brasileiros com DMD. Nosso objetivo principal foi elaborar uma atualização baseada em evidências sobre esses tópicos do consenso.

Variants in CLDN5 cause a syndrome characterized by seizures, microcephaly and brain calcifications.

The blood-brain barrier ensures CNS homeostasis and protection from injury. Claudin-5 (CLDN5), an important component of tight junctions, is critical for the integrity of the blood-brain barrier. We have identified de novo heterozygous missense variants in CLDN5 in 15 unrelated patients who presented with a shared constellation of features including developmental delay, seizures (primarily infantile onset focal epilepsy), microcephaly and a recognizable pattern of pontine atrophy and brain calcifications. All variants clustered in one subregion/domain of the CLDN5 gene and the recurrent variants demonstrate genotype-phenotype correlations. We modelled both patient variants and loss of function alleles in the zebrafish to show that the variants analogous to those in patients probably result in a novel aberrant function in CLDN5. In total, human patient and zebrafish data provide parallel evidence that pathogenic sequence variants in CLDN5 cause a novel neurodevelopmental disorder involving disruption of the blood-brain barrier and impaired neuronal function.

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.

Scientific rationale for a higher dose of nusinersen.

OBJECTIVE: The long-term favorable safety profile of nusinersen provides an opportunity to consider a higher dose. We report on the relationships between nusinersen cerebrospinal fluid (CSF) exposure, biomarker levels, and clinical efficacy. METHODS: The analyses used data from the CS3A and ENDEAR studies of nusinersen in participants with infantile-onset spinal muscular atrophy (SMA). Steady-state CSF trough (Ctrough ) levels, plasma phosphorylated neurofilament heavy chain (pNF-H) levels, body weight, and Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) scores were selected as parameters of interest. A validated population pharmacokinetic (PK) model was applied to predict the nusinersen CSF Ctrough . PK/pharmacodynamic (PK/PD) models used nusinersen CSF Ctrough measurements, which were time-matched with CHOP INTEND scores. RESULTS: Higher nusinersen CSF exposure was associated with a greater decrease in pNF-H levels and greater efficacy, as measured by change in the CHOP INTEND score from baseline. These findings indicate a dose-response relationship between CSF nusinersen levels and treatment response. The higher dose is predicted to lead to approximately a 2.4-fold increase in nusinersen CSF levels with fewer loading doses. PK/PD modeling indicates that a higher concentration of nusinersen may predict an additional 5-point increase in CHOP INTEND score beyond that observed with 12 mg. INTERPRETATION: Our data indicate that a higher dose of nusinersen may lead to additional clinically meaningful improvement in efficacy when compared with the currently approved 12-mg dose. The efficacy, safety, and PK of a higher nusinersen dose are currently under investigation in the ongoing phase 2/3 DEVOTE study (NCT04089566).

Efficacy of Caffeine in ADCY5-Related Dyskinesia: A Retrospective Study.

BACKGROUND: ADCY5-related dyskinesia is characterized by early-onset movement disorders. There is currently no validated treatment, but anecdotal clinical reports and biological hypotheses suggest efficacy of caffeine. OBJECTIVE: The aim is to obtain further insight into the efficacy and safety of caffeine in patients with ADCY5-related dyskinesia. METHODS: A retrospective study was conducted worldwide in 30 patients with a proven ADCY5 mutation who had tried or were taking caffeine for dyskinesia. Disease characteristics and treatment responses were assessed through a questionnaire. RESULTS: Caffeine was overall well tolerated, even in children, and 87% of patients reported a clear improvement. Caffeine reduced the frequency and duration of paroxysmal movement disorders but also improved baseline movement disorders and some other motor and nonmotor features, with consistent quality-of-life improvement. Three patients reported worsening. CONCLUSION: Our findings suggest that caffeine should be considered as a first-line therapeutic option in ADCY5-related dyskinesia. © 2022 International Parkinson and Movement Disorder Society.

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.

Sarcoglycanopathies: an update.

Sarcoglycanopathies are the most severe forms of autosomal recessive limb-girdle muscular dystrophies (LGMDs), constituting about 10-25% of LGMDs. The clinical phenotype is variable, but onset is usually in the first decade of life. Patients present muscle hypertrophy, elevated CK, variable muscle weaknesses, and progressive loss of ambulation. Four subtypes are known: LGMDR3, LGMDR4, LGMDR5 and LGMDR6, caused, respectively, by mutations in the SGCA, SGCB,SGCG and SGCD genes. Their four coded proteins, α-SG, ß-SG, λ-SG and δ-SG are part of the dystrophin-glycoprotein complex (DGC) present in muscle sarcolemma, which acts as a linker between the cytoskeleton of the muscle fiber and the extracellular matrix, providing mechanical support to the sarcolemma during myofiber contraction. Many different mutations have already been identified in all the sarcoglycan genes, with a predominance of some mutations in different populations. The diagnosis is currently based on the molecular screening for these mutations. Therapeutic approaches include the strategy of gene replacement mediated by a vector derived from adeno-associated virus (AAV). Pre-clinical studies have shown detectable levels of SG proteins in the muscle, and some improvement in the phenotype, in animal models. Therapeutic trials in humans are ongoing.

International retrospective natural history study of LMNA-related congenital muscular dystrophy.

Muscular dystrophies due to heterozygous pathogenic variants in LMNA gene cover a broad spectrum of clinical presentations and severity with an age of onset ranging from the neonatal period to adulthood. The natural history of these conditions is not well defined, particularly in patients with congenital or early onset who arguably present with the highest disease burden. Thus the definition of natural history endpoints along with clinically revelant outcome measures is essential to establishing both clinical care planning and clinical trial readiness for this patient group. We designed a large international cross-sectional retrospective natural history study of patients with genetically proven muscle laminopathy who presented with symptoms before two years of age intending to identify and characterize an optimal clinical trial cohort with pertinent motor, cardiac and respiratory endpoints. Quantitative statistics were used to evaluate associations between LMNA variants and distinct clinical events. The study included 151 patients (median age at symptom onset 0.9 years, range: 0.0-2.0). Age of onset and age of death were significantly lower in patients who never acquired independent ambulation compared to patients who achieved independent ambulation. Most of the patients acquired independent ambulation (n = 101, 66.9%), and subsequently lost this ability (n = 86; 85%). The age of ambulation acquisition (median: 1.2 years, range: 0.8-4.0) and age of ambulation loss (median: 7 years, range: 1.2-38.0) were significantly associated with the age of the first respiratory interventions and the first cardiac symptoms. Respiratory and gastrointestinal interventions occurred during first decade while cardiac interventions occurred later. Genotype-phenotype analysis showed that the most common mutation, p.Arg249Trp (20%), was significantly associated with a more severe disease course. This retrospective natural history study of early onset LMNA-related muscular dystrophy confirms the progressive nature of the disorder, initially involving motor symptoms prior to onset of other symptoms (respiratory, orthopaedic, cardiac and gastrointestinal). The study also identifies subgroups of patients with a range of long-term outcomes. Ambulatory status was an important mean of stratification along with the presence or absence of the p.Arg249Trp mutation. These categorizations will be important for future clinical trial cohorts. Finally, this study furthers our understanding of the progression of early onset LMNA-related muscular dystrophy and provides important insights into the anticipatory care needs of LMNA-related respiratory and cardiac manifestations.

MECP2-related conditions in males: A systematic literature review and 8 additional cases.

OBJECTIVE: To present a cohort of 8 males and perform a systematic review of all published cases with a single copy of MECP2 carrying a pathogenic variant. METHODS: We reviewed medical records of males with a single copy of MECP2 carrying a pathogenic variant. We searched in Medline (Pubmed) and Embase to collect all articles which included well-characterized males with a single copy of MECP2 carrying a pathogenic or likely pathogenic variant in MECP2 (1999-2020). RESULTS: The literature search yielded a total of 3,185 publications, of which 58 were included in our systematic review. We were able to collect information on 27 published patients with severe neonatal encephalopathy, 47 individuals with isolated or familial mental retardation X-linked 13 (XLMR13), as well as 24 individuals with isolated or familial Pyramidal signs, parkinsonism, and macroorchidism (PPM-X). In our cohort, we met eight individuals aged 4 to 19-year-old at the last evaluation. Three MECP2-associated phenotypes were seen in male carriers of a single copy of the gene: severe neonatal encephalopathy (n = 5); X-linked intellectual deficiency 13 (n = 2); and pyramidal signs, parkinsonism, and macroorchidism (PPM-X) (n = 1). Two novel de novo variants [p.(Gly252Argfs∗7) and p.(Tyr132Cys)] were detected. CONCLUSION: In males, the MECP2 pathogenic variants can be associated with different phenotypes, including neonatal severe encephalopathy, intellectual deficiency, or late-onset parkinsonism and spasticity. The typical RS phenotype is not expected in males, except in those with Klinefelter syndrome or somatic mosaicism for MECP2.

Association of Three Different Mutations in the CLCN1 Gene Modulating the Phenotype in a Consanguineous Family with Myotonia Congenita.

Myotonia congenita is a genetic disease caused by mutations in the CLCN1 gene, which encodes for the major chloride skeletal channel ClC-1, involved in the normal repolarization of muscle action potentials and consequent relaxation of the muscle after contraction. Two allelic forms are recognized, depending on the phenotype and the inheritance pattern: the autosomal dominant Thomsen disease with milder symptoms and the autosomal recessive Becker disorder with a severe phenotype. Before the recent advances of molecular testing, the diagnosis and genetic counseling of families was a challenge due to the large number of mutations in the CLCN1 gene, found both in homozygous or in heterozygous state. Here, we studied a consanguineous family in which three members presented a variable phenotype of myotonia, associated to a combination of three different mutations in the CLCN1 gene. A pathogenic splicing site mutation which causes the skipping of exon 17 was present in homozygosis in one very severely affected son. This mutation was present in compound heterozygosis in the consanguineous parents, but interestingly it was associated to a different second variant in the other allele: c.1453 A > G in the mother and c.1842 G > C in the father. Both displayed variable, but less severe phenotypes than their homozygous son. These results highlight the importance of analyzing the combination of different variants in the same gene in particular in families with patients displaying different phenotypes. This approach may improve the diagnosis, prognosis, and genetic counseling of the involved families.

Intragenic variants in the SMN1 gene determine the clinical phenotype in 5q spinal muscular atrophy.

OBJECTIVE: The aim of the study was to report the proportion of homozygous and compound heterozygous variants in the survival motor neuron 1 (SMN1) gene in a large population of patients with spinal muscular atrophy (SMA) and to correlate the severity of the disease with the presence of specific intragenic variants in SMN1 and with the SMN2 copy number. METHODS: Four hundred fifty Brazilian patients with SMA were included in a retrospective study, and clinical data were analyzed compared with genetic data; the SMN2 copy number was obtained by multiplex ligation-dependent probe amplification and pathogenic variants in SMN1 by next-generation sequencing. RESULTS: Four hundred two patients (89.3%) presented homozygous exon 7-SMN1 deletion, and 48 (10.7%) were compound heterozygous for the common deletion in one allele and a point mutation in the other allele. Recurrent variants in exons 3 and 6 (c.460C>T, c.770_780dup and c.734_735insC) accounted for almost 80% of compound heterozygous patients. Another recurrent pathogenic variant was c.5C>G at exon 1. Patients with c.770_780dup and c.734_735insC had a clinical phenotype correlated with SMN2 copy number, whereas the variants c.460C>T and c.5C>G determined a milder phenotype independently of the SMN2 copies. CONCLUSIONS: Patients with specific pathogenic variants (c.460C>T and c.5C>G) presented a milder phenotype, and the SMN2 copy number did not correlate with disease severity in this group.

Manifesting carriers of X-linked myotubular myopathy: Genetic modifiers modulating the phenotype.

OBJECTIVE: To analyze the modulation of the phenotype in manifesting carriers of recessive X-linked myotubular myopathy (XLMTM), searching for possible genetic modifiers. METHODS: Twelve Brazilian families with XLMTM were molecularly and clinically evaluated. In 2 families, 4 of 6 and 2 of 5 manifesting female carriers were identified. These females were studied for X chromosome inactivation. In addition, whole-exome sequencing was performed, looking for possible modifier variants. We also determined the penetrance rate among carriers of the mutations responsible for the condition. RESULTS: Mutations in the MTM1 gene were identified in all index patients from the 12 families, being 4 of them novel. In the heterozygotes, X chromosome inactivation was random in 3 of 4 informative manifesting carriers. The disease penetrance rate was estimated to be 30%, compatible with incomplete penetrance. Exome comparative analyses identified variants within a segment of 4.2 Mb on chromosome 19, containing the killer cell immunoglobulin-like receptor cluster of genes that were present in all nonmanifesting carriers and absent in all manifesting carriers. We hypothesized that these killer cell immunoglobulin-like receptor variants may modulate the phenotype, acting as a protective factor in the nonmanifesting carriers. CONCLUSIONS: Affected XLMTM female carriers have been described with a surprisingly high frequency for a recessive X-linked disease, raising the question about the pattern of inheritance or the role of modifier factors acting on the disease phenotype. We demonstrated the possible existence of genetic mechanisms and variants accountable for the clinical manifestation in these women, which can become future targets for therapies.

Dominant or recessive mutations in the RYR1 gene causing central core myopathy in Brazilian patients.

Central Core Disease (CCD) is an inherited neuromuscular disorder characterized by the presence of cores in muscle biopsy. CCD is caused by mutations in the RYR1 gene. This gene encodes the ryanodine receptor 1, which is an intracellular calcium release channel from the sarcoplasmic reticulum to the cytosol in response to depolarization of the plasma membrane. Mutations in this gene are also associated with susceptibility to Malignant Hyperthermia (MHS). In this study, we evaluated 20 families with clinical and histological characteristics of CCD to identify primary mutations in patients, for diagnosis and genetic counseling of the families. We identified variants in the RYR1 gene in 19/20 families. The molecular pathogenicity was confirmed in 16 of them. Most of these variants (22/23) are missense and unique in the families. Two variants were recurrent in two different families. We identified six families with biallelic mutations, five compound heterozygotes with no consanguinity, and one homozygous, with consanguineous parents, resulting in 30% of cases with possible autosomal recessive inheritance. We identified seven novel variants, four of them classified as pathogenic. In one family, we identified two mutations in exon 102, segregating in cis, suggesting an additive effect of two mutations in the same allele. This work highlights the importance of using Next-Generation Sequencing technology for the molecular diagnosis of genetic diseases when a very large gene is involved, associated to a broad distribution of the mutations along it. These data also influence the prevention through adequate genetic counseling for the families and cautions against malignant hyperthermia susceptibility.