2024 update: European consensus statement on gene therapy for spinal muscular atrophy.

Spinal muscular atrophy (SMA) is one of the most common genetic diseases and was, until recently, a leading genetic cause of infant mortality. Three disease-modifying treatments have dramatically changed the disease trajectories and outcome for severely affected infants (SMA type 1), especially when initiated in the presymptomatic phase. One of these treatments is the adeno-associated viral vector 9 (AAV9) based gene therapy onasemnogene abeparvovec (Zolgensma®), which is delivered systemically and has been approved by the European Medicine Agency for SMA patients with up to three copies of the SMN2 gene or with the clinical presentation of SMA type 1. While this broad indication provides flexibility in patient selection, it also raises concerns about the risk-benefit ratio for patients with limited or no evidence supporting treatment. In 2020, we convened a European neuromuscular expert working group to support the rational use of onasemnogene abeparvovec, employing a modified Delphi methodology. After three years, we have assembled a similar yet larger group of European experts who assessed the emerging evidence of onasemnogene abeparvovec's role in treating older and heavier SMA patients, integrating insights from recent clinical trials and real-world evidence. This effort resulted in 12 consensus statements, with strong consensus achieved on 9 and consensus on the remaining 3, reflecting the evolving role of onasemnogene abeparvovec in treating SMA.

Electrophysiological and Imaging Biomarkers to Evaluate Exercise Training in Patients with Neuromuscular Disease: A Systematic Review.

Exercise therapy as part of the clinical management of patients with neuromuscular diseases (NMDs) is complicated by the limited insights into its efficacy. There is an urgent need for sensitive and non-invasive quantitative muscle biomarkers to monitor the effects of exercise training. Therefore, the objective of this systematic review was to critically appraise and summarize the current evidence for the sensitivity of quantitative, non-invasive biomarkers, based on imaging and electrophysiological techniques, for measuring the effects of physical exercise training. We identified a wide variety of biomarkers, including imaging techniques, i.e., magnetic resonance imaging (MRI) and ultrasound, surface electromyography (sEMG), magnetic resonance spectroscopy (MRS), and near-infrared spectroscopy (NIRS). Imaging biomarkers, such as muscle maximum area and muscle thickness, and EMG biomarkers, such as compound muscle action potential (CMAP) amplitude, detected significant changes in muscle morphology and neural adaptations following resistance training. MRS and NIRS biomarkers, such as initial phosphocreatine recovery rate (V), mitochondrial capacity (Qmax), adenosine phosphate recovery half-time (ADP t1/2), and micromolar changes in deoxygenated hemoglobin and myoglobin concentrations (Δ[deoxy(Hb + Mb)]), detected significant adaptations in oxidative metabolism after endurance training. We also identified biomarkers whose clinical relevance has not yet been assessed due to lack of sufficient study.

Multifocal motor neuropathy is not associated with altered innate immune responses to endotoxin.

OBJECTIVE: Antibody- and complement-mediated peripheral nerve inflammation are central in the pathogenesis of MMN. Here, we studied innate immune responses to endotoxin in patients with MMN and controls to further our understanding of MMN risk factors and disease modifiers. METHODS: We stimulated whole blood of 52 patients with MMN and 24 controls with endotoxin and collected plasma. With a multiplex assay, we determined levels of the immunoregulating proteins IL-1RA, IL-1ß, IL-6, IL-10, IL-21, TNF-α, IL-8 and CD40L in unstimulated and LPS-stimulated plasma. We compared baseline and stimulated protein levels between patients and controls and correlated concentrations to clinical parameters. RESULTS: Protein level changes after stimulation were comparable between groups (p > 0.05). IL-1RA, IL-1ß, IL-6 and IL-21 baseline concentrations showed a positive correlation with monthly IVIg dosage (all corrected p-values < 0.016). Patients with anti-GM1 IgM antibodies showed a more pronounced IL-21 increase after stimulation (p 0.048). CONCLUSIONS: Altered endotoxin-induced innate immune responses are unlikely to be a susceptibility factor for MMN.

Primary SARS-CoV-2 infection in patients with immune-mediated inflammatory diseases: long-term humoral immune responses and effects on disease activity.

BACKGROUND: Patients with immune-mediated inflammatory diseases (IMIDs) on immunosuppressants (ISPs) may have impaired long-term humoral immune responses and increased disease activity after SARS-CoV-2 infection. We aimed to investigate long-term humoral immune responses against SARS-CoV-2 and increased disease activity after a primary SARS-CoV-2 infection in unvaccinated IMID patients on ISPs. METHODS: IMID patients on active treatment with ISPs and controls (i.e. IMID patients not on ISP and healthy controls) with a confirmed SARS-CoV-2 infection before first vaccination were included from an ongoing prospective cohort study (T2B! study). Clinical data on infections and increased disease activity were registered using electronic surveys and health records. A serum sample was collected before first vaccination to measure SARS-CoV-2 anti-receptor-binding domain (RBD) antibodies. RESULTS: In total, 193 IMID patients on ISP and 113 controls were included. Serum samples from 185 participants were available, with a median time of 173 days between infection and sample collection. The rate of seropositive IMID patients on ISPs was 78% compared to 100% in controls (p < 0.001). Seropositivity rates were lowest in patients on anti-CD20 (40.0%) and anti-tumor necrosis factor (TNF) agents (60.5%), as compared to other ISPs (p < 0.001 and p < 0.001, respectively). Increased disease activity after infection was reported by 68 of 260 patients (26.2%; 95% CI 21.2-31.8%), leading to ISP intensification in 6 out of these 68 patients (8.8%). CONCLUSION: IMID patients using ISPs showed reduced long-term humoral immune responses after primary SARS-CoV-2 infection, which was mainly attributed to treatment with anti-CD20 and anti-TNF agents. Increased disease activity after SARS-CoV-2 infection was reported commonly, but was mostly mild. TRIAL REGISTRATION: NL74974.018.20, Trial ID: NL8900. Registered on 9 September 2020.

Lung function decline preceding chronic respiratory failure in spinal muscular atrophy: a national prospective cohort study.

BACKGROUND: Progressive lung function decline, resulting in respiratory failure, is an important complication of spinal muscular atrophy (SMA). The ability to predict the need for mechanical ventilation is important. We assessed longitudinal patterns of lung function prior to chronic respiratory failure in a national cohort of treatment-naïve children and adults with SMA, hypothesizing an accelerated decline prior to chronic respiratory failure. METHODS: We included treatment-naïve SMA patients participating in a prospective national cohort study if they required mechanical ventilation because of chronic respiratory failure and if lung function test results were available from the years prior to initiation of ventilation. We analyzed Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 s (FEV1), Peak Expiratory Flow (PEF) and Maximum Expiratory Pressure (PEmax). We studied the longitudinal course using linear mixed-effects models. We compared patients who electively started mechanical ventilation compared to patients who could not be weaned after acute respiratory failure. RESULTS: We analyzed 385 lung function tests from 38 patients with SMA types 1c-3a. At initiation of ventilation median age was 18.8 years (IQR: 13.2-30.1) and median standardized FVC, FEV1 and PEF were 28.8% (95% CI: 23.5; 34.2), 28.8% (95% CI: 24.0; 33.7) and 30.0% (95% CI: 23.4; 36.7), with an average annual decline of 1.75% (95% CI: 0.86; 2.66), 1.72% (95% CI: 1.04; 2.40) and 1.65% (95% CI: 0.71; 2.59), respectively. Our data did not support the hypothesis of an accelerated decline prior to initiation of mechanical ventilation. Median PEmax was 35.3 cmH2O (95% CI: 29.4; 41.2) at initiation of mechanical ventilation and relatively stable in the years preceding ventilation. Median FVC, FEV1, PEF and PEmax were lower in patients who electively started mechanical ventilation (p < 0.001). CONCLUSIONS: Patterns of lung function decline cannot predict impending respiratory failure: SMA is characterized by a gradual decline of lung function. We found no evidence for an accelerated deterioration. In addition, PEmax remains low and stable in the years preceding initiation of ventilation. Patients who electively started mechanical ventilation had more restrictive lung function at initiation of ventilation, compared to patients who could not be weaned after surgery or a respiratory tract infection.

Magnetic resonance reveals mitochondrial dysfunction and muscle remodelling in spinal muscular atrophy.

Genetic therapy has changed the prognosis of hereditary proximal spinal muscular atrophy, although treatment efficacy has been variable. There is a clear need for deeper understanding of underlying causes of muscle weakness and exercise intolerance in patients with this disease to further optimize treatment strategies. Animal models suggest that in addition to motor neuron and associated musculature degeneration, intrinsic abnormalities of muscle itself including mitochondrial dysfunction contribute to the disease aetiology. To test this hypothesis in patients, we conducted the first in vivo clinical investigation of muscle bioenergetics. We recruited 15 patients and 15 healthy age and gender-matched control subjects in this cross-sectional clinico-radiological study. MRI and 31P magnetic resonance spectroscopy, the modality of choice to interrogate muscle energetics and phenotypic fibre-type makeup, was performed of the proximal arm musculature in combination with fatiguing arm-cycling exercise and blood lactate testing. We derived bioenergetic parameter estimates including: blood lactate, intramuscular pH and inorganic phosphate accumulation during exercise, and muscle dynamic recovery constants. A linear correlation was used to test for associations between muscle morphological and bioenergetic parameters and clinico-functional measures of muscle weakness. MRI showed significant atrophy of triceps but not biceps muscles in patients. Maximal voluntary contraction force normalized to muscle cross-sectional area for both arm muscles was 1.4-fold lower in patients than in controls, indicating altered intrinsic muscle properties other than atrophy contributed to muscle weakness in this cohort. In vivo31P magnetic resonance spectroscopy identified white-to-red remodelling of residual proximal arm musculature in patients on the basis of altered intramuscular inorganic phosphate accumulation during arm-cycling in red versus white and intermediate myofibres. Blood lactate rise during arm-cycling was blunted in patients and correlated with muscle weakness and phenotypic muscle makeup. Post-exercise metabolic recovery was slower in residual intramuscular white myofibres in patients demonstrating mitochondrial ATP synthetic dysfunction in this particular fibre type. This study provides the first in vivo evidence in patients that degeneration of motor neurons and associated musculature causing atrophy and muscle weakness in 5q spinal muscular atrophy type 3 and 4 is aggravated by disproportionate depletion of myofibres that contract fastest and strongest. Our finding of decreased mitochondrial ATP synthetic function selectively in residual white myofibres provides both a possible clue to understanding the apparent vulnerability of this particular fibre type in 5q spinal muscular atrophy types 3 and 4 as well as a new biomarker and target for therapy.

Gut microbial differences in breast and prostate cancer cases from two randomised controlled trials compared to matched cancer-free controls.

Implicated in several chronic diseases, the gastrointestinal microbiome is hypothesised to influence carcinogenesis. We compared faecal microbiota of newly diagnosed treatment-naïve overweight and obese cancer patients and matched controls. Cases were enrolled in presurgical weight-loss trials for breast (NCT02224807) and prostate (NCT01886677) cancers and had a body mass index (BMI) ≥25 kg/m2. Cancer-free controls were matched 1:1 by age (±5 years), race, gender, and BMI (±5 kg/m2). All participants provided faecal samples; isolated bacterial DNA were PCR amplified at the V4 region of the 16S rRNA gene and analysed using the QIIME pipeline. Tests compared cases versus controls, then separately by gender. Microbial alpha-diversity and beta-diversity were assessed, and relative abundance of Operational Taxonomic Units (OTU's) were compared at the genus level, with false discovery rate (FDR) correction. 22 overweight and obese cancer patients were matched with 22 cancer-free controls, with an average BMI of 30.5±4.3 kg/m2, age 54.4±5.3 years, and 54.5% were black. Fourteen matches were made between breast cancer cases and healthy female controls, and 8 matches were made with prostate cancer cases and healthy male controls. Comparison of all cases and controls revealed no differences in alpha diversity, though prostate cancer patients had higher Chao1 (P=0.006) and Observed Species (P=0.036) than cancer-free males. Beta-diversity metrics were significantly different between cases and controls (P<0.03 for all tests in whole sample and in men), though only unweighted Unifrac was different in women (P=0.005). Kruskal Wallis tests indicated significant differences among 16 genera in all matches, 9 in female, and 51 in male. This study suggests the faecal microbiota of treatment-naive breast and prostate cancer patients differs from controls, though larger samples are needed to substantiate these findings. Trial registration: NIH Clinical Trials, NCT01886677, NCT02224807, registered 26 June 2013, 25 Aug 2014 (respectively) - retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT01886677; https://clinicaltrials.gov/ct2/show/NCT02224807.

Biomarker profiles of endothelial activation and dysfunction in rare systemic autoimmune diseases: implications for cardiovascular risk.

OBJECTIVES: Vasculopathy is an important hallmark of systemic chronic inflammatory connective tissue diseases (CICTD) and is associated with increased cardiovascular risk. We investigated disease-specific biomarker profiles associated with endothelial dysfunction, angiogenic homeostasis and (tissue) inflammation, and their relation to disease activity in rare CICTD. METHODS: A total of 38 serum proteins associated with endothelial (dys)function and inflammation were measured by multiplex-immunoassay in treatment-naive patients with localized scleroderma (LoS, 30), eosinophilic fasciitis (EF, 8) or (juvenile) dermatomyositis (34), 119 (follow-up) samples during treatment, and 65 controls. Data were analysed by unsupervised clustering, Spearman correlations, non-parametric t test and ANOVA. RESULTS: The systemic CICTD, EF and dermatomyositis, had distinct biomarker profiles, with 'signature' markers galectin-9 (dermatomyositis) and CCL4, CCL18, CXCL9, fetuin, fibronectin, galectin-1 and TSP-1 (EF). In LoS, CCL18, CXCL9 and CXCL10 were subtly increased. Furthermore, dermatomyositis and EF shared upregulation of markers related to interferon (CCL2, CXCL10), endothelial activation (VCAM-1), inhibition of angiogenesis (angiopoietin-2, sVEGFR-1) and inflammation/leucocyte chemo-attraction (CCL19, CXCL13, IL-18, YKL-40), as well as disturbance of the Angiopoietin-Tie receptor system and VEGF-VEGFR system. These profiles were related to disease activity, and largely normalized during treatment. However, a subgroup of CICTD patients showed continued elevation of CXCL10, CXCL13, galectin-9, IL-18, TNFR2, VCAM-1, and/or YKL-40 during clinically inactive disease, possibly indicating subclinical interferon-driven inflammation and/or endothelial dysfunction. CONCLUSION: CICTD-specific biomarker profiles revealed an anti-angiogenic, interferon-driven environment during active disease, with incomplete normalization under treatment. This warrants further investigation into monitoring of vascular biomarkers during clinical follow-up, or targeted interventions to minimize cardiovascular risk in the long term.

Long-term follow-up of patients with type 2 and non-ambulant type 3 spinal muscular atrophy (SMA) treated with olesoxime in the OLEOS trial.

In a previous Phase 2 study, olesoxime had a favorable safety profile. Although the primary endpoint was not met, analyses suggested that olesoxime might help in the maintenance of motor function in patients with Types 2/3 SMA. This open-label extension study (OLEOS) further characterizes the safety, tolerability and efficacy of olesoxime over longer therapy durations. In OLEOS, no new safety risks were identified. Compared to matched natural history data, patients treated with olesoxime demonstrated small, non-significant changes in motor function over 52 weeks. Motor function scores were stable for 52 weeks but declined over the remainder of the study. The greatest decline in motor function was seen in patients ≤15 years old, and those with Type 2 SMA had faster motor function decline versus those with Type 3 SMA. Previous treatment with olesoxime in the Phase 2 study was not protective of motor function in OLEOS. Respiratory outcomes were stable in patients with Type 3 SMA >15 years old but declined in patients with Type 2 SMA and in patients with Type 3 SMA ≤15 years old. Overall, with no stabilization of functional measures observed over 130 weeks, OLEOS did not support significant benefit of olesoxime in patients with SMA.

Feeding and Swallowing Problems in Infants with Spinal Muscular Atrophy Type 1: an Observational Study.

BACKGROUND: Infantile hereditary proximal spinal muscular atrophy (SMA) type 1 is characterized by onset in the first 6 months of life and severe and progressive muscle weakness. Dysphagia is a common complication but has not been studied in detail. OBJECTIVE: To study feeding and swallowing problems in infants with SMA type 1, and to explore the relation between these problems and functional motor scores. METHODS: We prospectively included 16 infants with SMA type 1 between September 2016 and October 2018. Eleven infants received palliative care and five infants best supportive care in combination with nusinersen. We compiled and used an observation list with feeding related issues and observed feeding sessions during inpatient and outpatient visits. The Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) was used as a measure of motor function. RESULTS: All infants in the palliative care group (median onset of disease 14 days (range 1-56); median inclusion in the study 52 days (range 16-252) demonstrated symptoms of fatigue during feeding and unsafe swallowing. Symptoms were short nursing sessions (10-15 minutes), and not being able to finish the recommended feeding volumes (72%); increased frequency of feeding sessions (55%); coughing when drinking or eating (91%), and wet breathing during and after feeding (64%).Two out of five infants in the nusinersen group (median onset of disease 38 days (range 21-90); inclusion in the study at 63 days (range 3-218) were clinically pre-symptomatic at the start of treatment. The other three infants showed symptoms of fatigue and unsafe swallowing at inclusion in the study. These symptoms initially decreased after the start of the treatment, but (re)appeared in all five infants between the ages of 8 to 12 months, requiring the start tube of feeding. In the same period motor function scores significantly improved (median increase CHOP INTEND 16 points). CONCLUSION: Impaired feeding and swallowing remain important complications in infants with SMA type 1 after the start of nusinersen. Improvement of motor function does not imply similar gains in bulbar function.

Analysis of FUS, PFN2, TDP-43, and PLS3 as potential disease severity modifiers in spinal muscular atrophy.

OBJECTIVE: To investigate mutations in genes that are potential modifiers of spinal muscular atrophy (SMA) severity. METHODS: We performed a hypothesis-based search into the presence of variants in fused in sarcoma (FUS), transactive response DNA-binding protein 43 (TDP-43), plastin 3 (PLS3), and profilin 2 (PFN2) in a cohort of 153 patients with SMA types 1-4, including 19 families. Variants were detected with targeted next-generation sequencing and confirmed with Sanger sequencing. Functional effects of the identified variants were analyzed in silico and for PLS3, by analyzing expression levels in peripheral blood. RESULTS: We identified 2 exonic variants in FUS exons 5 and 6 (p.R216C and p.S135N) in 2 unrelated patients, but clinical effects were not evident. We identified 8 intronic variants in PLS3 in 33 patients. Five PLS3 variants (c.1511+82T>C; c.748+130 G>A; c.367+182C>T; c.891-25T>C (rs145269469); c.1355+17A>G (rs150802596)) potentially alter exonic splice silencer or exonic splice enhancer sites. The variant c.367+182C>T, but not RNA expression levels, corresponded with a more severe phenotype in 1 family. However, this variant or level of PLS3 expression did not consistently correspond with a milder or more severe phenotype in other families or the overall cohort. We found 3 heterozygous, intronic variants in PFN2 and TDP-43 with no correlation with clinical phenotype or effects on splicing. CONCLUSIONS: PLS3 and FUS sequence variants do not modify SMA severity at the population level. Specific variants in individual patients or families do not consistently correlate with disease severity.

Nutritional ketosis improves exercise metabolism in patients with very long-chain acyl-CoA dehydrogenase deficiency.

A maladaptive shift from fat to carbohydrate (CHO) oxidation during exercise is thought to underlie myopathy and exercise-induced rhabdomyolysis in patients with fatty acid oxidation (FAO) disorders. We hypothesised that ingestion of a ketone ester (KE) drink prior to exercise could serve as an alternative oxidative substrate supply to boost muscular ATP homeostasis. To establish a rational basis for therapeutic use of KE supplementation in FAO, we tested this hypothesis in patients deficient in Very Long-Chain acyl-CoA Dehydrogenase (VLCAD). Five patients (range 17-45 y; 4 M/1F) patients were included in an investigator-initiated, randomised, blinded, placebo-controlled, 2-way cross-over study. Patients drank either a KE + CHO mix or an isocaloric CHO equivalent and performed 35 minutes upright cycling followed by 10 minutes supine cycling inside a Magnetic Resonance scanner at individual maximal FAO work rate (fatmax; approximately 40% VO2 max). The protocol was repeated after a 1-week interval with the alternate drink. Primary outcome measures were quadriceps phosphocreatine (PCr), Pi and pH dynamics during exercise and recovery assayed by in vivo 31 P-MR spectroscopy. Secondary outcomes included plasma and muscle metabolites and respiratory gas exchange recordings. Ingestion of KE rapidly induced mild ketosis and increased muscle BHB content. During exercise at FATMAX, VLCADD-specific plasma acylcarnitine levels, quadriceps glycolytic intermediate levels and in vivo Pi/PCr ratio were all lower in KE + CHO than CHO. These results provide a rational basis for future clinical trials of synthetic ketone ester supplementation therapy in patients with FAO disorders. Trial registration: ClinicalTrials.gov. Protocol ID: NCT03531554; METC2014.492; ABR51222.042.14.

Natural course of scoliosis and lifetime risk of scoliosis surgery in spinal muscular atrophy.

OBJECTIVE: To investigate the natural course of scoliosis and to estimate lifetime probability of scoliosis surgery in spinal muscular atrophy (SMA). METHODS: We analyzed cross-sectional data from 283 patients from our population-based cohort study. Additional longitudinal data on scoliosis progression and spinal surgery were collected from 36 consecutive patients who received scoliosis surgery at our center. RESULTS: The lifetime probability of receiving scoliosis surgery was ≈80% in SMA types 1c and 2. Patients with type 2 who only learned to sit (type 2a) were significantly younger at time of surgery than those who learned to sit and stand (type 2b). The lifetime risk of surgery was lower in type 3a (40%) and strongly associated with age at loss of ambulation: 71% in patients losing ambulation before 10 years of age vs 22% losing ambulation after the age of 10 years (p = 0.005). In type 3a, preserving the ability to walk 1 year longer corresponded to a 15% decrease in lifetime risk of scoliosis surgery (hazard ratio 0.852, p = 0.017). Scoliosis development was characterized by initial slow progression, followed by acceleration in the 1.5- to 2-year period before surgery. CONCLUSION: The lifetime probability of scoliosis surgery is high in SMA types 1c and 2 and depends on age at loss of ambulation in type 3. Motor milestones such as standing that are not part of the standard classification system are of additional predictive value. Our data may act as a reference to assess long-term effects of new SMA-specific therapies.

Serum cytokine patterns in immunoglobulin m monoclonal gammopathy-associated polyneuropathy.

INTRODUCTION: Polyneuropathy with immunoglobulin M monoclonal gammopathy (IgM-PNP) is associated with the presence of IgM antibodies against nerve constituents such as myelin associated glycoprotein (MAG) and gangliosides. METHODS: To test whether B-cell-stimulating cytokines are increased in IgM-PNP, we measured serum concentrations of 11 cytokines in 81 patients with IgM-PNP and 113 controls. RESULTS: Median interleukin (IL)-6 concentrations were higher in patients with IgM-PNP, and median IL-10 concentrations were higher in the subgroup with anti-MAG IgM antibodies. These serum concentrations were not increased in 110 patients with multifocal motor neuropathy. DISCUSSION: Median IL-6 and IL-10 serum concentrations differ between patients with anti-MAG neuropathy and other patients with IgM-PNP compared with healthy and neuropathy controls. These differences may indicate differences in immune-mediated disease mechanisms. Muscle Nerve 59:694-698, 2019.

Impact of newborn screening for very-long-chain acyl-CoA dehydrogenase deficiency on genetic, enzymatic, and clinical outcomes.

Most infants with very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD) identified by newborn screening (NBS) are asymptomatic at the time of diagnosis and remain asymptomatic. If this outcome is due to prompt diagnosis and initiation of therapy, or because of identification of individuals with biochemical abnormalities who will never develop symptoms, is unclear. Therefore, a 10-year longitudinal national cohort study of genetically confirmed VLCADD patients born before and after introduction of NBS was conducted. Main outcome measures were clinical outcome parameters, acyl-CoA dehydrogenase very long chain gene analysis, VLCAD activity, and overall capacity of long-chain fatty acid oxidation (LC-FAO flux) in lymphocytes and cultured skin fibroblasts. Median VLCAD activity in lymphocytes of 54 patients, 21 diagnosed pre-NBS and 33 by NBS was, respectively, 5.4% (95% confidence interval [CI]: 4.0-8.3) and 12.6% (95% CI: 10.7-17.7; P < 0.001) of the reference mean. The median LC-FAO flux was 33.2% (95% CI: 22.8-48.3) and 41% (95% CI: 40.8-68; P < 0.05) of the control mean, respectively. Clinical characteristics in 23 pre-NBS and 37 NBS patients revealed hypoglycemic events in 12 vs 2 patients, cardiomyopathy in 5 vs 4 patients and myopathy in 14 vs 3 patients. All patients with LC-FAO flux <10% developed symptoms. Of the patients with LC-FAO flux >10% 7 out of 12 diagnosed pre-NBS vs none by NBS experienced hypoglycemic events. NBS has a clear beneficial effect on the prevention of hypoglycemic events in patients with some residual enzyme activity, but does not prevent hypoglycemia nor cardiac complications in patients with very low residual enzyme activity. The effect of NBS on prevalence and prevention of myopathy-related complications remains unclear.

Altered Energetics of Exercise Explain Risk of Rhabdomyolysis in Very Long-Chain Acyl-CoA Dehydrogenase Deficiency.

Rhabdomyolysis is common in very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) and other metabolic myopathies, but its pathogenic basis is poorly understood. Here, we show that prolonged bicycling exercise against a standardized moderate workload in VLCADD patients is associated with threefold bigger changes in phosphocreatine (PCr) and inorganic phosphate (Pi) concentrations in quadriceps muscle and twofold lower changes in plasma acetyl-carnitine levels than in healthy subjects. This result is consistent with the hypothesis that muscle ATP homeostasis during exercise is compromised in VLCADD. However, the measured rates of PCr and Pi recovery post-exercise showed that the mitochondrial capacity for ATP synthesis in VLCADD muscle was normal. Mathematical modeling of oxidative ATP metabolism in muscle composed of three different fiber types indicated that the observed altered energy balance during submaximal exercise in VLCADD patients may be explained by a slow-to-fast shift in quadriceps fiber-type composition corresponding to 30% of the slow-twitch fiber-type pool in healthy quadriceps muscle. This study demonstrates for the first time that quadriceps energy balance during exercise in VLCADD patients is altered but not because of failing mitochondrial function. Our findings provide new clues to understanding the risk of rhabdomyolysis following exercise in human VLCADD.

Cytokine profiles in multifocal motor neuropathy and progressive muscular atrophy.

Multifocal motor neuropathy (MMN) and progressive muscular atrophy (PMA) are associated with IgM monoclonal gammopathy or the presence IgM anti-GM1-antibodies. To further investigate the pathophysiology of MMN and PMA we determined concentrations of 16 mainly B-cell associated inflammatory markers in serum from 25 patients with MMN, 55 patients with PMA, 25 patients with amyotrophic lateral sclerosis (ALS) and 50 healthy controls. Median serum concentrations of the 16 tested cytokines and chemokines were not significantly increased in patients with MMN or patients with PMA, irrespective of the presence of IgM monoclonal gammopathy or high IgM anti-GM1 antibodies. These results argue against a systemic B-cell mediated immune response underlying the pathogenesis of MMN and PMA.

RYR1-related myopathies: a wide spectrum of phenotypes throughout life.

BACKGROUND AND PURPOSE: Although several recent studies have implicated RYR1 mutations as a common cause of various myopathies and the malignant hyperthermia susceptibility (MHS) trait, many of these studies have been limited to certain age groups, confined geographical regions or specific conditions. The aim of the present study was to investigate the full spectrum of RYR1-related disorders throughout life and to use this knowledge to increase vigilance concerning malignant hyperthermia. METHODS: A retrospective cohort study was performed on the clinical, genetic and histopathological features of all paediatric and adult patients in whom an RYR1 mutation was detected in a national referral centre for both malignant hyperthermia and inherited myopathies (2008-2012). RESULTS: The cohort of 77 non-related patients (detection rate 28%) included both congenital myopathies with permanent weakness and 'induced' myopathies such as MHS and non-anaesthesia-related episodes of rhabdomyolysis or hyperCKemia, manifested throughout life and triggered by various stimuli. Sixty-one different mutations were detected, of which 24 were novel. Some mutations are present in both dominant (MHS) and recessive modes (congenital myopathy) of inheritance, even within families. Histopathological features included an equally wide spectrum, ranging from only subtle abnormalities to prominent cores. CONCLUSIONS: This broad range of RYR1-related disorders often presents to the general paediatric and adult neurologist. Its recognition is essential for genetic counselling and improving patients' safety during anaesthesia. Future research should focus on in vitro testing by the in vitro contracture test and functional characterization of the large number of RYR1 variants whose precise effects currently remain uncertain.

Fcγ receptor IIIA genotype is associated with rituximab response in antimyelin-associated glycoprotein neuropathy.

BACKGROUND: Treatment with anti-B cell antibody rituximab may ameliorate the disease course in a subgroup of patients with polyneuropathy associated with IgM monoclonal gammopathy. Polymorphisms of leukocyte IgG receptors (FcγR) that influence efficiency of antibody-dependent cell-mediated cytotoxicity determine rituximab efficacy in patients with lymphoma and autoimmune disease. OBJECTIVE: To investigate the association of FcγRIIA and FcγRIIIA polymorphisms with the response to rituximab treatment in a cohort of patients with polyneuropathy associated with IgM monoclonal gammopathy (PNP-IgM) with and without antimyelin-associated glycoprotein antibodies. METHODS: We determined FcγRIIA-R/H131 and FcγRIIIA-V/F158 genotypes in 27 patients with PNP-IgM using allele-specific PCR and Sanger sequencing. RESULTS: The FcγRIIIA-V/V158 genotype was associated with functional improvement (p=0.02) after 1 year. CONCLUSIONS: FcγRIIIA polymorphisms are potential biomarkers for response to rituximab treatment in polyneuropathy associated with IgM monoclonal gammopathy.