Biallelic variants in SNUPN cause a limb girdle muscular dystrophy with myofibrillar-like features.

Alterations in RNA-splicing are a molecular hallmark of several neurological diseases, including muscular dystrophies where mutations in genes involved in RNA metabolism or characterised by alterations in RNA splicing have been described. Here, we present five patients from two unrelated families with a limb-girdle muscular dystrophy (LGMD) phenotype carrying a biallelic variant in SNUPN gene. Snurportin-1, the protein encoded by SNUPN, plays an important role in the nuclear transport of small nuclear ribonucleoproteins (snRNPs), essential components of the spliceosome. We combine deep phenotyping, including clinical features, histopathology and muscle magnetic resonance image (MRI), with functional studies in patient-derived cells and muscle biopsies to demonstrate that variants in SNUPN are the cause of a new type of LGMD according to current definition. Moreover, an in vivo model in Drosophila melanogaster further supports the relevance of Snurportin-1 in muscle. SNUPN patients show a similar phenotype characterised by proximal weakness starting in childhood, restrictive respiratory dysfunction and prominent contractures, although interindividual variability in terms of severity even in individuals from the same family was found. Muscle biopsy showed myofibrillar-like features consisting of myotilin deposits and Z-disc disorganisation. MRI showed predominant impairment of paravertebral, vasti, sartorius, gracilis, peroneal and medial gastrocnemius muscles. Conservation and structural analyses of Snurportin-1 p.Ile309Ser variant suggest an effect in nuclear-cytosol snRNP trafficking. In patient-derived fibroblasts and muscle, cytoplasmic accumulation of snRNP components is observed, while total expression of Snurportin-1 and snRNPs remains unchanged, which demonstrates a functional impact of SNUPN variant in snRNP metabolism. Furthermore, RNA-splicing analysis in patients' muscle showed widespread splicing deregulation, in particular in genes relevant for muscle development and splicing factors that participate in the early steps of spliceosome assembly. In conclusion, we report that SNUPN variants are a new cause of limb girdle muscular dystrophy with specific clinical, histopathological and imaging features, supporting SNUPN as a new gene to be included in genetic testing of myopathies. These results further support the relevance of splicing-related proteins in muscle disorders.

Genetic landscape of congenital insensitivity to pain and hereditary sensory and autonomic neuropathies.

Congenital insensitivity to pain (CIP) and hereditary sensory and autonomic neuropathies (HSAN) are clinically and genetically heterogeneous disorders exclusively or predominantly affecting the sensory and autonomic neurons. Due to the rarity of the diseases and findings based mainly on single case reports or small case series, knowledge about these disorders is limited. Here, we describe the molecular workup of a large international cohort of CIP/HSAN patients including patients from normally under-represented countries. We identify 80 previously unreported pathogenic or likely pathogenic variants in a total of 73 families in the >20 known CIP/HSAN-associated genes. The data expand the spectrum of disease-relevant alterations in CIP/HSAN, including novel variants in previously rarely recognized entities such as ATL3-, FLVCR1- and NGF-associated neuropathies and previously under-recognized mutation types such as larger deletions. In silico predictions, heterologous expression studies, segregation analyses and metabolic tests helped to overcome limitations of current variant classification schemes that often fail to categorize a variant as disease-related or benign. The study sheds light on the genetic causes and disease-relevant changes within individual genes in CIP/HSAN. This is becoming increasingly important with emerging clinical trials investigating subtype or gene-specific treatment strategies.

[Myositis: from diagnosis to treatment]. / Myositis: von der Diagnose zur Therapie.

BACKGROUND: Inflammatory diseases of the skeletal muscle are important, often severe diseases with a considerable impact on the quality of life. In addition to muscle weakness there is often involvement of other organs, such as the heart, lungs and esophagus with symptoms such as dyspnea or dysphagia. PURPOSE: A fast and effective treatment is only possible by an early and reliable diagnosis according to current national and international standards. METHODS: The diagnostic repertoire includes autoantibody testing, imaging, muscle biopsy, detection of extramuscular manifestations, e.g., by high-resolution lung computed tomography (CT) and an individualized tumor search. An optimal treatment and the avoidance of irreversible damage, such as a loss of walking ability, are only possible through a good interdisciplinary cooperation including neurology or pediatrics, rheumatology, dermatology, neuropathology, pulmonology and cardiology. RESULTS: In addition to standard immunosuppression with glucocorticosteroids, azathioprine or methotrexate, escalation treatment with rituximab is now well established. Interdisciplinary treatment according to national and international standards, such as guidelines on myositis, should be coordinated at qualified centers of excellence. DISCUSSION: Helpful resources are the MYOSITIS NETZ ( www.myositis-netz.de ) and the International Myositis Society (iMyoS; www.imyos.org ).

Neuromuscular conditions and the impact of cystine-depleting therapy in infantile nephropathic cystinosis: A cross-sectional analysis of 55 patients.

Infantile nephropathic cystinosis (INC) is a rare lysosomal storage disease caused by biallelic mutations in the cystinosin gene, leading to cystine accumulation in various organs. The aim of this cross-sectional study was to investigate neuromuscular complications in a cohort of 55 patients (aged 2.8-41.3 years, median 18.5 years) with INC. Clinical examination, jumping mechanography, clinical neurophysiology, and muscle/nerve ultrasound were performed. Physical performance, measured by mechanography, was below average in all patients. However, this reduction in physical performance was not always detected by conventional muscle power assessment. Twenty-eight percent of patients had mostly mild axial weakness of the neck flexors and/or of the abdominal rectus muscles, the latter often presenting during childhood. One adult patient had generalized muscle weakness. Two patients had evidence of specific neuromuscular conditions, which may not have been directly related to cystinosis. 30% of patients presented with mild, 7% with moderate, and 5% with severe weakness of the intrinsic muscles of the hand. Muscle wasting was more pronounced in the older cystinosis patients with multiple organ complications. Sonographic increase in muscle echogenicity corresponded only with severe weakness. Electromyography of the intrinsic hand muscles, performed in selected patients, showed myopathic, neurogenic, or mixed myopathic-neurogenic abnormalities. A particularly important finding of this study is that the neuromuscular complications were largely independent from both the age of initiation of pharmacological cystine-depleting therapy and from adherence to treatment. Significant correlation was observed between better physical performance in jumping and cysteine levels in leukocytes.

Mechanography in children: pediatric references in postural control.

OBJECTIVE: To establish pediatric age- and sex-specific references for measuring postural control with a mechanography plate in a single centre, prospective, normative data study. METHODS: 739 children and adolescents (396 male/343 female) aged 4 to 17 years were studied. Each participant completed the following test sequence three times: Romberg, semi-tandem, tandem, each with eyes open and closed, and a one-leg stand with eyes open, and a single two-legged jump. Normal ranges were determined based on percentile calculations using the LMS method. Results from the two-legged jump were compared to a reference population the single two-legged jump (s2LJ) assessment in 2013. RESULTS: 38 different equilibrium parameters calculated were analysed. Of all parameters Path Length, vCoFmean, Equilibrium Score and Sway Angle showed a low variation within the same age group but high dependency on age and were thus chosen for automated balance assessment. CONCLUSION: Standard values of postural control in healthy children derived from automated balance testing using a mechanography plate were successfully acquired and a subset of parameters for automated balance assessment identified.

[Newborn screening program for spinal muscular atrophy]. / Neugeborenenscreeningprogramm für die spinale Muskelatrophie.

BACKGROUND: The introduction of a comprehensive newborn screening program for spinal muscular atrophy (SMA), specifically for 5q-SMA, is planned for the end of 2021 in Germany. Several targeted treatment options have become available for all patients with SMA. MATERIAL AND METHODS: Newborn screening for 5q-SMA is based on the detection of a homozygous deletion of exon 7 in the SMN1 gene by molecular genetic analysis from the dried blood card. In all cases a second blood sample must be drawn as a part of confirmation diagnostics including the determination of the SMN2 copy numbers. RESULTS: Insights from pilot projects performed in parts of Germany are presented. Advantages and disadvantages of the screening project are discussed. CONCLUSION: Consultation and treatment should be carried out in a department of neuropediatrics with experience in the treatment of children with 5q-SMA, which is able to provide all current treatment options for the child, so that, when necessary, the treatment can be started within the first month of life.

Safety and efficacy of nusinersen in spinal muscular atrophy: The EMBRACE study.

INTRODUCTION: The EMBRACE study (Clinical Trials No. NCT02462759) evaluated nusinersen in infants/children with infantile- or later-onset spinal muscular atrophy (SMA) who were ineligible for the ENDEAR and CHERISH studies. METHODS: Participants were randomized to intrathecal nusinersen (12-mg scaled equivalent dose; n = 14) or sham procedure (n = 7) in part 1 (~14 months) and subsequently received open-label nusinersen for ~24 months in part 2 of the study. RESULTS: Part 1 was stopped early after the demonstration of motor function benefit with nusinersen in ENDEAR. There were no nusinersen-related adverse events (AEs) and no study discontinuations due to nusinersen-related AEs. The most common AEs included pyrexia, cough, pneumonia, and upper respiratory tract infections. Motor milestone responder rates were higher in those receiving nusinersen at last available assessment (93%) than in those receiving sham procedure in part 1 (29%) or transitioned from sham to nusinersen in part 2 (83%). This functional improvement was observed despite the small sample size and shortened part 1 trial duration that undermined the power of the study to demonstrate such treatment effects at a significant level. DISCUSSION: Nusinersen demonstrated a favorable long-term benefit-risk profile in this broad population of individuals with infantile- or later-onset SMA.

Jumping Mechanography is a Suitable Complementary Method to Assess Motor Function in Ambulatory Boys with Duchenne Muscular Dystrophy.

OBJECTIVE: The number of clinical trials for Duchenne muscular dystrophy (DMD) has increased substantially lately, therefore appropriate clinical instruments are needed to measure disease progression and drug efficacy. Jumping mechanography is a medical diagnostic method for motion analysis, which allows to quantify physical parameters. In this study, we compared mechanography with timed function tests (TFTs). METHODS: 41 ambulatory DMD patients performed a total of 95 chair rising tests (CRT) and a total of 76 single two-legged jumps (S2LJ) on a mechanography ground reaction force platform. The results were correlated with a 6-minute walk test (6MWT) and the time required to run 10 meters, stand up from a supine position, and climb four stairs, all performed in the same setting. RESULTS: Our measurements show a high correlation between mechanography and the TFTs: S2LJ/10-m run, r = 0.62; CRT/10-m run, r = 0.61; S2LJ/standing up from supine, r = 0.48; CRT/standing up from supine, r = 0.58; S2LJ/climb four stairs, r = 0.55; CRT/climb four stairs, r = 0.51. The correlation between mechanography and the 6MWT was only moderate with r = 0.38 for S2LJ/6MWT and r = 0.39 for CRT/6MWT. INTERPRETATION: Jumping mechanography is a reliable additional method, which can be used for physical endpoint measurements in clinical trials. We confirmed our assumption, that the method provides additional information concerning performance at movement with higher power output. We suggest using the S2LJ as a first-choice tandem tool combined with the 6MWT. In patients with higher disability, the CRT is an alternative measuring method, because with the progression of the disease this is longer feasible.

Is Exercise-Induced Fatigue a Problem in Children with Duchenne Muscular Dystrophy?

OBJECTIVE: Duchenne muscular dystrophy (DMD) is a devastating X-linked muscular disorder. The number of studies investigating new therapeutic approaches is substantially increasing. This study aims to investigate the impact and diagnostic value of exercise-induced fatigue in DMD, which has been proposed as a suitable outcome parameter in other conditions like spinal muscular atrophy. PATIENTS AND METHODS: A cohort of 55 DMD patients (49 of them treated with steroids and 9 with ataluren) underwent a total of 241 6MWT (mean 4.4 tests/patient) which were retrospectively analyzed. Exercise-induced fatigue was assessed by the ratio between the distance achieved in the sixth minute and the distance in the second minute of the 6MWT. In previous studies a quotient above 1 was defined as a sign of fatigue. RESULTS: The average fatigue quotient in the whole cohort of patients was 1.0. In a further analysis no impact of age, steroid therapy, ataluren therapy, overall disability, and distance in the 6-minute walk test (6MWT) on fatigue in DMD patients could be shown. CONCLUSION: Our data show that fatigue does not play a relevant role in DMD. Analysis of fatigue is not a useful outcome parameter in DMD studies. For this reason we suggest the 2MWT, which is better accepted by the patients, as an alternative to the commonly 6MWT.

Diagnosis and Care of Infants and Children with Pompe Disease.

Pompe disease is a rare metabolic myopathy caused by deficiency of lysosomal α-glucosidase. Reduced enzyme activity results in abnormal intra- and extralysosomal glycogen deposition as well as impaired cellular function and autophagy. Age at manifestation and severity of disease depend on residual enzyme activity. Enzyme replacement therapy (ERT) is available since 2006. In infantile onset Pompe disease, the most severe form, markedly prolonged survival has resulted in a new phenotype with symptoms and problems not encountered previously. In addition, it became apparent that antibody formation against the recombinant human enzyme may adversely affect the response to ERT. This review summarizes new knowledge gained in the last years concerning care of pediatric patients with Pompe disease and gives recommendations for diagnostics, treatment, and follow-up.

[Recommendations for gene therapy of spinal muscular atrophy with onasemnogene abeparvovec-AVXS-101 : Consensus paper of the German representatives of the Society for Pediatric Neurology (GNP) and the German treatment centers with collaboration of the medical scientific advisory board of the German Society for Muscular Diseases (DGM)]. / Handlungsempfehlungen zur Gentherapie der spinalen Muskelatrophie mit Onasemnogene Abeparvovec ­ AVXS-101 : Konsensuspapier der deutschen Vertretung der Gesellschaft für Neuropädiatrie (GNP) und der deutschen Behandlungszentren unter Mitwirkung des Medizinisch-Wissenschaftlichen Beirates der Deutschen Gesellschaft für Muskelkranke (DGM) e. V.

BACKGROUND: Spinal muscular atrophy (SMA) is a severe, life-limiting neurodegenerative disease. A disease-modifying and approved therapy with nusinersen has been available in Germany since July 2017. Gene therapies offer another promising treatment option through a once in a lifetime administration. In May 2019 a gene replacement therapy for the treatment of SMA was approved for the first time by the U.S. Food and Drug Administration (FDA). An application for approval in Europe has been submitted and is currently pending. OBJECTIVE: This consensus paper was compiled at the invitation of the German Society for Muscular Diseases (DGM) with the participation of all potential German neuromuscular treatment centers, the German section of the Society for Pediatric Neurology (GNP) and with the involvement of the medical scientific advisory board of the DGM. The aim was to define and establish the necessary prerequisites for a safe and successful application of the new gene replacement therapy in clinical practice. CONCLUSION: Gene replacement therapy with onasemnogene abeparvovec has the potential to significantly influence the course of SMA. Long-term data on sustainability of effects and possible adverse effects of gene replacement therapy are not yet available. The application of this innovative therapy must be carried out in specialized and appropriately qualified treatment centers under strict safety conditions. This article makes suggestions for the necessary framework conditions and gives recommendations for a systematic pretreatment and posttreatment assessment schedule under gene therapy. The effectiveness and safety of the therapy should be systematically documented in an industry-independent and disease-specific register.

[Molecular therapies in childhood neuromuscular disorders-definite hope versus unknown pitfalls]. / Molekulare Therapien bei neuromuskulären Erkrankungen im Kindesalter ­ Große Hoffnungen und unbekannte Risiken.

Spinal muscular atrophy and muscular dystrophy Duchenne belong to the group of rare neuromuscular diseases manifesting in early childhood. Therapeutic options for some of these rare monogenic diseases have changed significantly in recent years. Molecular therapies such as direct gene transfer or alternative processing of the disease-specific gene play an important role in this transformation.In particular, the course of 5q-associated spinal muscle atrophy has changed significantly due to the availability of such causal therapies, while the results of ongoing studies are still pending for most muscle diseases. In the area of neuromuscular diseases, an achievable therapeutic goal is to slow the progression, but not complete healing. Currently, only limited data are available. In particular, the long-term effectiveness and the possible risks are still unknown. Therefore, these therapies should be used under strictly monitored conditions.

[Analysis of motor development within the first year of life: 3-D motion tracking without markers for early detection of developmental disorders]. / Analyse der Spontanmotorik im 1. Lebensjahr: Markerlose 3-D-Bewegungserfassung zur Früherkennung von Entwicklungsstörungen.

Children with motor development disorders benefit greatly from early interventions. An early diagnosis in pediatric preventive care (U2-U5) can be improved by automated screening. Current approaches to automated motion analysis, however, are expensive, require lots of technical support, and cannot be used in broad clinical application. Here we present an inexpensive, marker-free video analysis tool (KineMAT) for infants, which digitizes 3­D movements of the entire body over time allowing automated analysis in the future.Three-minute video sequences of spontaneously moving infants were recorded with a commercially available depth-imaging camera and aligned with a virtual infant body model (SMIL model). The virtual image generated allows any measurements to be carried out in 3­D with high precision. We demonstrate seven infants with different diagnoses. A selection of possible movement parameters was quantified and aligned with diagnosis-specific movement characteristics.KineMAT and the SMIL model allow reliable, three-dimensional measurements of spontaneous activity in infants with a very low error rate. Based on machine-learning algorithms, KineMAT can be trained to automatically recognize pathological spontaneous motor skills. It is inexpensive and easy to use and can be developed into a screening tool for preventive care for children.

NAXE Mutations Disrupt the Cellular NAD(P)HX Repair System and Cause a Lethal Neurometabolic Disorder of Early Childhood.

To safeguard the cell from the accumulation of potentially harmful metabolic intermediates, specific repair mechanisms have evolved. APOA1BP, now renamed NAXE, encodes an epimerase essential in the cellular metabolite repair for NADHX and NADPHX. The enzyme catalyzes the epimerization of NAD(P)HX, thereby avoiding the accumulation of toxic metabolites. The clinical importance of the NAD(P)HX repair system has been unknown. Exome sequencing revealed pathogenic biallelic mutations in NAXE in children from four families with (sub-) acute-onset ataxia, cerebellar edema, spinal myelopathy, and skin lesions. Lactate was elevated in cerebrospinal fluid of all affected individuals. Disease onset was during the second year of life and clinical signs as well as episodes of deterioration were triggered by febrile infections. Disease course was rapidly progressive, leading to coma, global brain atrophy, and finally to death in all affected individuals. NAXE levels were undetectable in fibroblasts from affected individuals of two families. In these fibroblasts we measured highly elevated concentrations of the toxic metabolite cyclic-NADHX, confirming a deficiency of the mitochondrial NAD(P)HX repair system. Finally, NAD or nicotinic acid (vitamin B3) supplementation might have therapeutic implications for this fatal disorder.

SACS variants are a relevant cause of autosomal recessive hereditary motor and sensory neuropathy.

Mutations in the SACS gene have been initially reported in a rare autosomal recessive cerebellar ataxia syndrome featuring prominent cerebellar atrophy, spasticity and peripheral neuropathy as well as retinal abnormalities in some cases (autosomal recessive spastic ataxia of Charlevoix-Saguenay, ARSACS). In the past few years, the phenotypic spectrum has broadened, mainly owing to the availability and application of high-throughput genetic testing methods. We identified nine patients (three sib pairs, three singleton cases) with isolated, non-syndromic hereditary motor and sensory neuropathy (HMSN) who carried pathogenic SACS mutations, either in the homozygous or compound heterozygous state. None of the patients displayed spasticity or pyramidal signs. Ataxia, which was noted in only three patients, was consistent with a sensory ataxia. Nerve conduction and nerve biopsy studies showed mixed demyelinating and axonal neuropathy. Brain MRI scans were either normal or revealed isolated upper vermis atrophy of the cerebellum. Our findings confirm the broad clinical spectrum associated with SACS mutations, including pure polyneuropathy without characteristic clinical and brain imaging manifestations of ARSACS.

PRUNE1 Deficiency: Expanding the Clinical and Genetic Spectrum.

BACKGROUND: Primary microcephaly and profound global developmental delay have been considered the core clinical phenotype in patients with bi-allelic PRUNE1 mutations. METHODS: Linkage analysis and whole-exome sequencing (WES) in a multiplex family and extraction of further cases from a WES repository containing 571 children with severe developmental disabilities and neurologic symptoms. RESULTS: We identified bi-allelic PRUNE1 mutations in twelve children from six unrelated families. All patients who survived beyond the first 6 months of life had early-onset global developmental delay, bilateral spastic paresis, dysphagia and difficult-to-treat seizures, while congenital or later-evolving microcephaly was not a consistent finding. Brain MRI showed variable anomalies with progressive cerebral and cerebellar atrophies and T2-hyperintense brain stem lesions. Peripheral neuropathy was documented in five cases. Disease course was progressive in all patients and eight children died in the first or early second decade of life. In addition to the previously reported missense mutation p.(Asp106Asn), we observed a novel homozygous missense variant p.(Leu172Pro) and a homozygous contiguous gene deletion encompassing most of the PRUNE1 gene and part of the neighboring BNIPL gene. CONCLUSIONS: PRUNE1 deficiency causes severe early-onset disease affecting the central and peripheral nervous systems. Microcephaly is probably not a universal feature.

Overlap phenotype between CMT1A and hereditary neuropathy with liability to pressure palsies caused by the novel small in-frame deletion c.407_418del12 in PMP22 gene.

We report monozygotic twins, who presented with a clinical picture of Charcot-Marie-Tooth disease type 1 (CMT1) with bilateral foot drop, pes cavus, thoracic kyphosis, and scoliosis. Hereditary neuropathy with liability to pressure palsies (HNPP) showed up in one of them. Neurography showed demyelinating neuropathy, typical for CMT1, and transient conduction block in the ulnar nerve correlating with clinical ulnar palsy due to minor mechanical stress in only one of them. Genetic analysis revealed novel small de novo deletion c.407_418del12 in the PMP22 gene. Our patient shows the rarely reported combination of CMT1A and HNPP, caused by an in-frame deletion in the PMP22 gene. HNPP is in the majority of cases correlated with heterozygous deletion of the whole PMP22 gene or other mutations leading to functional haploinsufficiency. The cases give further evidence that pathogenesis of HNPP is not completely understood and can obviously result from existence of a defective protein, too. The intrafamiliar phenotypic variability, even in monozygotic twins, confirms the well-known fact that factors apart from genetics contribute to the clinical course.

Long-Term Observations in an Affected Family with Neurogenic Scapuloperoneal Syndrome Caused by Mutation R269C in the TRPV4 Gene.

Mutations in the TRPV4 gene, encoding a polymodal Ca(2+) permeable channel, are causative for several human diseases, affecting the skeletal and the peripheral nervous system with highly variable phenotypes. We report on a family with two affected individuals. The father clinically suffered from a classical scapuloperoneal syndrome, while the son presented with a severe neonatal onset with congenital respiratory distress, feeding problems and arthrogryposis multiplex. Multi-Gene Panel sequencing by next generation sequencing revealed the heterozygous mutation c.805C>T (p.R269C) in the TRPV4 gene. Long-term observation over two decades showed no relevant disease progression in the father and, after a dramatic neonatal period, a significant improvement in the son who became ambulant with orthoses at the age of 5 years, suggesting a reasonably good prognosis even in cases with severe neonatal onset. Long-term findings in muscle ultrasound correlated with the clinical course, showing stable or even slightly improved findings. Neurography revealed a late-onset sensory neuropathy in the father, which was so far not described in TRPV4 neuropathies.

Impaired Neurodevelopment in Children with 5q-SMA - 2 Years After Newborn Screening.

OBJECTIVE: Numerous studies have consistently found that reduced SMN protein expression does not severely affect cognitive function in SMA patients. However, the average intelligence quotient of SMA patients has ranged above to below average in different studies. The cognitive development of SMA patients identified through newborn screening remains largely unknown. METHODS: 40 of 47 eligible SMA patients (23 females/17 males) from 39 families identified through newborn screening between January 2018 and December 2020 underwent developmental testing using Bayley III (BSID) after the 2 years of age. The mean age was 29.25 months (23-42 months). 17 patients had 2, 11 patients had 3 and 12 patients had ≥4 copies of SMN2. RESULTS: cognitive scale: mean 94.55 (SD 24.01); language scale: mean 86.09 (SD 26.41); motor scale: 81.28 (SD 28.07). Overall, the cognitive scales show that 14 children were below average, 20 children were average and 6 children were above average. 10/14 children with below average scores had 2 SMN2 copies. The post-hoc pairwise comparisons showed that the cognition main scale was significantly more sensitive to the number of SMN2 copies than the motor main scale of the BSID (MΔ= 10.27, p = 0.014). There is also evidence that cognition scored higher than the language main scale (MΔ= 7.11, p = 0.090). CONCLUSION: The impaired cognitive development of SMA children with 2 SMN2 copies, despite early initiation of therapy, underscores the critical role of the SMN protein in the early stages of brain development.

270th ENMC International Workshop: Consensus for SMN2 genetic analysis in SMA patients 10-12 March, 2023, Hoofddorp, the Netherlands.

The 270th ENMC workshop aimed to develop a common procedure to optimize the reliability of SMN2 gene copy number determination and to reinforce collaborative networks between molecular scientists and clinicians. The workshop involved neuromuscular and clinical experts and representatives of patient advocacy groups and industry. SMN2 copy number is currently one of the main determinants for therapeutic decision in SMA patients: participants discussed the issues that laboratories may encounter in this molecular test and the cruciality of the accurate determination, due the implications as prognostic factor in symptomatic patients and in individuals identified through newborn screening programmes. At the end of the workshop, the attendees defined a set of recommendations divided into four topics: SMA molecular prognosis assessment, newborn screening for SMA, SMN2 copies and treatments, and modifiers and biomarkers. Moreover, the group draw up a series of recommendations for the companies manufacturing laboratory kits, that will help to minimize the risk of errors, regardless of the laboratories' expertise.