Translational Research Studies in Exercise-related Muscle Disorders

Translational research is the process that transfers knowledge from basic sciences to the clinical setting. This PhD thesis translates knowledge gained from animal model research in hypokalaemic periodic paralysis (HypoPP) and McArdle disease to humans affected by these conditions to identify new treatment options for both diseases. The efficacy of two compounds, sodium valproate and bumetanide, were assessed for the first time in humans with McArdle disease and HypoPP, respectively. For HypoPP, the role of the McManis test as an outcome measure was explored in a randomised, double-blind, placebo-controlled phase II clinical trial with a cross-over design. For McArdle disease, several outcome measures were explored in an open-label proof-of-concept phase II study. 2 mg bumetanide was not effective to abort a focal attack of weakness in an immobilised hand in the majority of the trial participants with HypoPP, but data presented here supports further studies of bumetanide in this population of patients. Extending the isometric exercise period to 10 minutes increased the sensitivity of the McManis test, and frequent compound muscle action potential (CMAP) amplitude assessments were shown to be useful in assessing both efficacy and safety. 20 mg/kg/day sodium valproate was ineffective in stimulating the expression of the brain glycogen phosphorylase enzyme in skeletal muscle of people with McArdle disease. Based on these results, further research into VPA as a treatment for McArdle disease is discouraged. The combination of several outcome measures contributed to data interpretation and should be considered in future studies exploring treatment efficacy in McArdle disease. The results of this research should contribute to future clinical trials in the field of exercise-related muscle disorders and provide valuable insights for translational research

Misdiagnosis is an important factor for diagnostic delay in McArdle disease

Diagnosis of McArdle disease is frequently delayed by many years following the first presentation of symptoms to a health professional. The aim of this study was to investigate the importance of misdiagnosis in delaying diagnosis of McArdle disease. The frequency of misdiagnosis, duration of diagnostic delay, categories of misdiagnoses and inappropriate medical interventions were assessed in 50 genetically confirmed patients. The results demonstrated a high frequency of misdiagnosis (90%, n = 45/50) most commonly during childhood years (67%; n = 30/45) compared with teenage years and adulthood (teenage: n = 7/45; adult n = 5/45; not known n = 3/45). The correct diagnosis of McArdle disease was rarely made before adulthood (median age of diagnosis 33 years). Thirty-one patients (62%) reported having received more than one misdiagnosis; the most common were “growing pains” (40%, n = 20) and “laziness/being unfit” (46%, n = 23). A psychiatric/psychological misdiagnosis was significantly more common in females than males (females 6/20; males 1/30; p < 0.01). Of the 45 patients who were misdiagnosed, 21 (47%) received incorrect management. This study shows that most patients with McArdle disease received an incorrect explanation of their symptoms providing evidence that misdiagnosis plays an important part in delaying implementation of appropriate medical advice and management to this group of patients.The authors would like to thank Mr Andrew Wakelin for his great and inspiring work. The authors would also like to thank AGSD-UK, CAPES Foundation, Muscular Dystrophy Campaign and the Euromac Registry for their support

From exercise intolerance to functional improvement: The second wind phenomenon in the identification of McArdle disease

McArdle disease is the most common of the glycogen storage diseases. Onset of symptoms is usually in childhood with muscle pain and restricted exercise capacity. Signs and symptoms are often ignored in children or put down to 'growing pains' and thus diagnosis is often delayed. Misdiagnosis is not uncommon because several other conditions such as muscular dystrophy and muscle channelopathies can manifest with similar symptoms. A simple exercise test performed in the clinic can however help to identify patients by revealing the second wind phenomenon which is pathognomonic of the condition. Here a patient is reported illustrating the value of using a simple 12 minute walk test.RSS is funded by Ciências sem Fronteiras/CAPES Foundation. The authors would like to thank the Association for Glycogen Storage Disease (UK), the EUROMAC Registry funded by the European Union, the Muscular Dystrophy Campaign, the NHS National Specialist Commissioning Group and the Myositis Support Group for funding

Polymyositis without Beneficial Response to Steroid Therapy:Should Miyoshi Myopathy be a Differential Diagnosis?

Patient: Male, 16 Final Diagnosis: Miyoshi myopathy Symptoms: HyperCKemia • myalgia • weakness Medication: — Clinical Procedure: — Specialty: Neurology OBJECTIVE: Rare disease BACKGROUND: Miyoshi myopathy (MM) is an autosomal-recessive muscle disorder caused by mutations in the DYSF gene. Clinical features and histopathological changes in dysferlinopathies may mimic inflammatory myopathies and a high degree of clinical suspicion is required to guide the genetic investigation. CASE REPORT: We report the case of a 16-year-old male who presented with severe bilateral calf pain and elevated CK levels (15 000 IU/l) who was on prolonged steroid therapy prompted by the clinical suspicion of inflammatory myopathy. Three years into his illness, he was referred for neuromuscular evaluation presenting with untreatable muscle pain and progressive weakness. The diagnosis of “refractory polymyositis” was revisited. Targeted exome sequencing revealed homozygous pathogenic mutations in the DYSF gene, confirming a diagnosis of Miyoshi myopathy. CONCLUSIONS: Our case illustrates that severe muscle pain may be the initial feature of Miyoshi myopathy and should be considered in the differential diagnosis of inflammatory myopathies. Although the described patient reported partial clinical improvement in muscle pain, steroid treatment is not an effective therapy for dysferlinopathy patients and it did not prevent disease progression. In addition, we confirm the utility of next-generation sequencing approaches to myopathies, particularly in complex or unusual cases when muscle biopsy is not available

Rhabdomyolysis:A genetic perspective

Rhabdomyolysis (RM) is a clinical emergency characterized by fulminant skeletal muscle damage and release of intracellular muscle components into the blood stream leading to myoglobinuria and, in severe cases, acute renal failure. Apart from trauma, a wide range of causes have been reported including drug abuse and infections. Underlying genetic disorders are also a cause of RM and can often pose a diagnostic challenge, considering their marked heterogeneity and comparative rarity. In this paper we review the range of rare genetic defects known to be associated with RM. Each gene has been reviewed for the following: clinical phenotype, typical triggers for RM and recommended diagnostic approach. The purpose of this review is to highlight the most important features associated with specific genetic defects in order to aid the diagnosis of patients presenting with hereditary causes of recurrent RM

APPLICABILITY OF THE COBB ANGLE MEASUREMENT IN IDIOPATHIC SCOLIOSIS USING SCANNED IMAGING

ABSTRACT Objectives: To compare the measurement of the Cobb angle on printed radiographs and on scanned radiographs viewed through the software "PixViewer". Methods: Preoperative radiographs of 23 patients were evaluated on printed films and through the software "PixViewer". The same evaluator, a spine surgeon, chose the proximal and distal limiting vertebrae of the main curve on printed radiographs, without identification of patients, and measured the Cobb angle based on these parameters. The same parameters and measurements were applied to scanned radiographs. The measurements were compared, as well as the choice of limiting vertebrae. Results: The average variation of the Cobb angle between methods was 1.48 ± 1.73°. The intraclass correlation coefficient (ICC) was 0.99, demonstrating excellent reproducibility. Conclusion: The Cobb method can be used to evaluate scoliosis through the "PixViewer" tool with the same reliability as the classic method on printed radiographs

Two-year efficacy and safety of risdiplam in patients with type 2 or non-ambulant type 3 spinal muscular atrophy (SMA)

The original version of this article unfortunately contained a mistake. The corrected details are given below for your reading. In figure 1, there is an error in the n numbers below the graph in Panel 1b for the placebo group. The n numbers underneath Panel 1b should be 58 58 50. There is an error within Fig. 4. The dashed lines at ~ − 1.4 should be at 0. They have been moved downwards and are no longer in the correct place. The corrected Figs. 1 and 4 are given in the following page. (Figure presented.) (Figure presented.) Change from baseline in MFM32 total score in patients treated with risdiplam for up to 24 months and those who previously received placebo until study month 12. aThirty-one percent (55/180) of the SUNFISH intent-to-treat population were 2–5 years old at baseline. b± 95% CI. cBaseline is the last measurement prior to the first dose of risdiplam or placebo. dData cut-off: 30 Sep 2020. eData cut-off: 6 Sep 2019. fPatients in the placebo arm received placebo for 12 months followed by risdiplam treatment for 12 months. gNumber of patients with valid results = number of patients with an available total score (result) at respective time points. Intent-to-treat patients. hPatients in the placebo arm received placebo for 12 months followed by risdiplam treatment for 12 months. Placebo period not shown in this graph. CI confidence interval, MFM32 32-item motor function measure Change in caregiver- and patient-reported SMAIS upper limb total score from baseline in patients receiving risdiplam for up to 24 months and those who previously received placebo up to study month 12. a± 95% CI. Baseline is the last measurement prior to the first dose of risdiplam or placebo. bData cut-off: 30 Sep 2020. cData cut-off: 6 Sep 2019. dPatients in the placebo arm received placebo for 12 months followed by risdiplam treatment for 12 months. Risdiplam period not shown in this graph. eNumber of patients with valid results = number of patients with an available total score (result) at respective time points. Intent-to-treat patients. SMAIS scores range from 0 to 44 following rescoring to a 0–2 response scale for each item. Higher scores indicate greater independence in completing daily activities. CI confidence interval, SMA spinal muscular atrophy, SMAIS SMA Independence Scale, SMAIS-ULM SMA Independence Scale-Upper Limb Module.SCOPUS: er.jinfo:eu-repo/semantics/publishe