Vacuolar Myopathy Research Articles

Autophagic vacuolar myopathy: Danon disease and related myopathies

AbstractAutophagic vacuolar myopathy is a subgroup of muscle diseases defined as a condition in which autophagic vacuoles are present as a muscle pathological feature and is caused by abnormality of autophagy in skeletal muscles. There is an autophagic vacuolar myopathy characterized by the presence of specific autophagic vacuoles known as autophagic vacuoles with sarcolemmal features (AVSF). It is referred to as AVSF myopathy and includes Danon disease and related myopathies. Danon disease is an X‐linked dominant disease associated with a primary deficiency of lysosomal‐associated membrane protein 2 in which severe hypertrophic cardiomyopathy and myopathy develop. Cardiomyopathy is a determinant prognostic factor of this disease, and heart transplantation is still the sole radical treatment. The pathomechanism of AVSF myopathy is considered to be caused by abnormality of autophagy resulting from primary lysosomal dysfunction.

Early onset calsequestrin defect: A new phenotype with limb asymmetry

Calsequestrin (CASQ) represents the main Ca2+ buffer in the sarcoplasmic reticulum The CASQ1 and CASQ2 isoforms are preferentially expressed in skeletal and cardiac/smooth muscle, CASQ1 is largely predominant in fast-twitch (type II) fibers. CASQ1 buffers Ca2+ and prevents it from precipitating, maintaining large-capacity gradient release large amounts of Ca2+ on stimulus. The first human myopathy associated with CASQ1 mutations was only recently reported: a founder mutation (c.731A>G, p.Asp244Gly) was first described in patients presenting a non-debilitating vacuolar myopathy, we report an early-onset case with the same mutation, but early-onset new phenotype.

NEW GENES AND DISEASES: EP.304 Early onset lower limp assymmetry: a new clinical phenotype of calsequestrin mutation

Calsequestrin is a protein that handles calcium in sarcoplasmic reticulum (SR),Ca2+ transients are crucial in skeletal muscle excitation-contraction coupling. Synchronous Ca2+ release from the SR terminal cisternae into the cytoplasm and its reuptake into the SR store are granted by a structural and functional unit and their defect causes myopathy. In an 11-year-old girl, affected by lower limb asymmetry (R limb shorter of 3 cm), upper limb hypotrophy and winging scapulae were found; she had high CK:2900 U/l, her sister presented myalgias and CK:1500 U/l, the mother CK 500 U/l and grandmother had both congenital club foot. We investigated the causes of the high CK by EMG that was myopathic, muscle biopsy that showed few atrophic fibres, in ATPase rare 2C fibres, some increased NADH-TR stain at the periphery, increased central nuclei and rare basophilic fibres. We performed immunohistochemistry for dystrophin, caveolin-3, alpha-sarcoglycan, western blot for dysferlin: all normal. The girl was operated at 15 years for elongation of right femur and by epiphysiodesis left femur and the limb asymmetry was reduced to only half a centimeter: however she complained of fatiguability, especially after physical education at school, and high CK (2186 U). She presented with scoliosis, difficulty walking with calf hypertrophy. A search for the causes for hyperCKemia was done with WGS at TIGEM and resulted in detection of a pathogenetic variant of CASQ1 gene (p.ASP244Gly), coding for calsequestrin, which allowed the solution of this puzzling familial case. In 7 members of 4 Italian families with vacuolar myopathy with CASQ1 mutation calsequestrin aggregates and a similar variant was found. In CASQ1 myopathy in several cases hyperCKemia, myalgia or other vague symptoms are present: in 22 CASQ1-mutated patients from 12 families 21 sharing the same variant of our case presented symptoms in the sixth decade with exercise intolerance and myalgias and later developed mild to moderate, slowly progressive proximal weakness with quadriceps atrophy and scapular winging. In the present family, clubfoot, early onset, limb asymmetry were the predominant clinical symptoms, they could be the effect of somatic mosaicism. In this respect our patient presents an early onset and a new clinical phenotype of lower limb asymmetry that is unique. The present familial case expands the clinical phenotype of CASQ1-myopathy.

CHANNELOPATHIES AND RELATED DISORDERS: EP.225 Autosomal dominant early onset vacuolar myopathy with granular material, without periodic paralysis, associated with c.1583C>A CACNA1S gene mutation

Dominant mutations in CACNA1S gene mainly causes hypokalemic periodic paralysis (PP)(hypoPP). We report a patient with progressive early onset myopathy associated with heterozygous CACNA1S mutation and aim to extend the description of phenotypical spectrum of CACNA1S-related muscle diseases. A 68-year-old man developed progressive proximal weakness from the age of 35 years. He had four siblings including an affected brother. His mother had PP and became wheelchair bound at 55 years. CK level was elevated (<1.5 upper normal value). Electroneuromyography showed axonal sensorimotor polyneuropathy and myogenic potentials. Thigh magnetic resonance imaging showed extensive muscle fatty replacement and muscle biopsy showed atrophic fibers with vacuoles containing granular material. Clinical exome identified the heterozygous c.1583G>A well-known pathogenic variant in CACNA1S. The patient's brother had PP from the age of 27. Neurological examination was normal at the age of 39. Muscle biopsy showed a vacuolar myopathy with granular material. No further medical information was available. The patient died at the age of 72 yrs. Molecular characterisation was not achieved. CACNA1S-HypoPP evolving to fixed myopathy in late adulthood is well described but isolated progressive myopathy was only exceptionally reported and never with an onset <50 years. We hereby report the earliest “myopathy onset” ever described, enlarging the phenotypical spectrum of CACNA1S-related myopathies and suggest considering it even in young adult-onset myopathies, especially when granular vacuoles are present.

OTHER NMDs: EP.349 GFPT1-related myopathy overlapping with autophagic vacuolar myopathy. A case report

Autophagic vacuolar myopathies are a heterogeneous group of muscle diseases with a common denominator of altered autophagy and defective protein quality control. Pathogenic variants in GFPT1 cause limb-girdle congenital myasthenic syndrome. Muscle biopsies from affected patients usually show characteristic tubular aggregates, fiber disproportion, and in limited reports, autophagic vacuoles. A 27-year-old female born to non-consanguineous parents, presented with a progressive axial and limb-girdle weakness from 22 months of age, without cognitive impairment. She developed a progressive dorsolumbar scoliosis and restrictive respiratory pattern from 4 years of age. CK levels were normal and EMG without RNS revealed a myopathic pattern. The muscle biopsy showed variable fiber size and large numbers of fibres containing single or multiple cytoplasmic vacuoles containing cellular debris. Oxidative activity was increased in those fibers. Muscle MRI revealed generalized atrophy predominantly in axial and limb-girdle muscles. Trio-WES analysis failed to find pathogenic variants in genes related to autophagic vacuolar myopathy, but research-based reanalysis identified a homozygous pathogenic variant in GFPT1 (NM_001244710.1 c.686-2A>G). RNS revealed a mild and inconstant area decrement at trapezius muscle and SFEMG a pathological jitter with blocks at extensor digitorum communis, consistent with the diagnosis of congenital myasthenic syndrome. Treatment with pyridostigmine and 2,4-diaminopyrimidine was initiated with mild improvement. She is now able to walk independently indoors holding her head, without respiratory or oropharyngeal concerns. The initial diagnosis of autophagic vacuolar myopathy based on the presence of autophagic vacuoles delayed the genetic diagnosis and treatment in this case. We propose the inclusion of GFPT1 under the umbrella of autophagic vacuolar myopathies and encourage a deeper study of the GFPT1 function in autophagy.

Autophagy is affected in patients with hypokalemic periodic paralysis: an involvement in vacuolar myopathy?

Hypokalemic periodic paralysis is an autosomal dominant, rare disorder caused by variants in the genes for voltage-gated calcium channel CaV1.1 (CACNA1S) and NaV1.4 (SCN4A). Patients with hypokalemic periodic paralysis may suffer from periodic paralysis alone, periodic paralysis co-existing with permanent weakness or permanent weakness alone. Hypokalemic periodic paralysis has been known to be associated with vacuolar myopathy for decades, and that vacuoles are a universal feature regardless of phenotype. Hence, we wanted to investigate the nature and cause of the vacuoles. Fourteen patients with the p.R528H variation in the CACNA1S gene was included in the study. Histology, immunohistochemistry and transmission electron microscopy was used to assess general histopathology, ultrastructure and pattern of expression of proteins related to muscle fibres and autophagy. Western blotting and real-time PCR was used to determine the expression levels of proteins and mRNA of the proteins investigated in immunohistochemistry. Histology and transmission electron microscopy revealed heterogenous vacuoles containing glycogen, fibrils and autophagosomes. Immunohistochemistry demonstrated autophagosomes and endosomes arrested at the pre-lysosome fusion stage. Expression analysis showed a significant decrease in levels of proteins an mRNA involved in autophagy in patients, suggesting a systemic effect. However, activation level of the master regulator of autophagy gene transcription, TFEB, did not differ between patients and controls, suggesting competing control over autophagy gene transcription by nutritional status and calcium concentration, both controlling TFEB activity. The findings suggest that patients with hypokalemic periodic paralysis have disrupted autophagic processing that contribute to the vacuoles seen in these patients.

ATG14 and RB1CC1 play essential roles in maintaining muscle homeostasis

ABSTRACT Defects in macroautophagy/autophagy are implicated in the pathogenesis of neuromuscular and heart diseases. To precisely define the roles of autophagy-related genes in skeletal and cardiac muscles, we generated muscle-specific rb1cc1- and atg14-conditional knockout (cKO) mice by using Ckm/Ckmm2-Cre and compared their phenotypes to those of ulk1 ulk2-conditional double-knockout (cDKO) mice. atg14-cKO mice developed hypertrophic cardiomyopathy, which was associated with abnormal accumulation of autophagic cargoes in the heart and early mortality. Skeletal muscles of both atg14-cKO and rb1cc1-cKO mice showed features of autophagic vacuolar myopathy with ubiquitin+ SQSTM1+ deposits, but only those of rb1cc1-cKO mice showed TARDBP/TDP-43+ pathology and other features of the inclusion body myopathy–like disease we previously described in ulk1 ulk2-cDKO mice. Herein, we highlight tissue-specific differences between skeletal and cardiac muscles in their reliance on core autophagy proteins and unique roles for ULK1-ULK2 and RB1CC1 among these proteins in the development of TARDBP+ pathology. ABBREVIATIONS:AVM: autophagic vacuolar myopathy; cDKO: conditional double knockout; cKO: conditional knockout; H&E: hematoxylin and eosin; IBM: inclusion body myopathy; mtDNA: mitochondrial DNA; PFA: paraformaldehyde; RNP: ribonucleoprotein; TBST: Tris-buffered saline with 0.2% Triton X-100

Pathological mechanisms of vacuolar aggregate myopathy arising from a Casq1 mutation.

Mice with a mutation (D244G, DG) in calsequestrin 1 (CASQ1), analogous to a human mutation in CASQ1 associated with a delayed onset human myopathy (vacuolar aggregate myopathy), display a progressive myopathy characterized by decreased activity, decreased ability of fast twitch muscles to generate force and low body weight after one year of age. The DG mutation causes CASQ1 to partially dissociate from the junctional sarcoplasmic reticulum (SR) and accumulate in the endoplasmic reticulum (ER). Decreased junctional CASQ1 reduces SR Ca2+ release. Muscles from older DG mice display ER stress, ER expansion, increased mTOR signaling, inadequate clearance of aggregated proteins by the proteasomes, and elevation of protein aggregates and lysosomes. This study suggests that the myopathy associated with the D244G mutation in CASQ1 is driven by CASQ1 mislocalization, reduced SR Ca2+ release, CASQ1 misfolding/aggregation and ER stress. The subsequent maladaptive increase in protein synthesis and decreased protein aggregate clearance are likely to contribute to disease progression.

A novel deletion in the C-terminal region of HSPB8 in a family with rimmed vacuolar myopathy.

Heat shock protein family B member 8, encoded by HSPB8, is an essential component of the chaperone-assisted selective autophagy complex, which maintains muscle function by degrading damaged proteins in the cells. Mutations in HSPB8 have been reported to cause Charcot-Marie-Tooth type 2L, distal hereditary motor neuropathy IIa, and rimmed vacuolar myopathies (RVM). In this study, we identified a novel heterozygous frameshift variant c.525_529del in HSPB8 in a large Japanese family with RVM, using whole exome sequencing. Three affected individuals had severe respiratory failure, which has not been addressed by previous studies. Muscle atrophy in the paraspinal muscles was also a clinical feature of the individuals affected with RVM in this study. The frameshift mutation was located in the last coding exon, and the mutated protein was predicted to harbor an isoleucine-leucine-valine (ILV) sequence, which corresponds to the IXI/V (isoleucine, X amino acids, and isoleucine or valine) motif. The IXI/V motif is essential for assembly into larger oligomers in other small heat shock proteins and all frameshift mutants of HSPB8 were predicted to share the ILV sequence in the C-terminal extension. The in silico prediction tools showed low protein solubility and increased aggregation propensity for the region around the ILV sequence. The IXI/V motif might be associated with the pathogenesis of HSPB8-related RVM.

Creatine transport and pathological changes in creatine transporter deficient mice.

The severe impact on brain function and lack of effective therapy for patients with creatine (Cr) transporter deficiency motivated the generation of three ubiquitous Slc6a8 deficient mice (-/y). While each mouse knock-out line has similar behavioral effects at 2 to 3 months of age, other features critical to the efficient use of these mice in drug discovery are unclear or lacking: the concentration of Cr in brain and heart differ widely between mouse lines, there are limited data on histopathologic changes, and no data on Cr uptake. Here, we determined survival, measured endogenous Cr and uptake of its deuterium-labeled analogue Cr-d3 using a liquid chromatography coupled with tandem mass spectrometry assay, and performed comprehensive histopathologic examination on the Slc6a8-/y mouse developed by Skelton et al. Our results show that Slc6a8-/y mice have widely varying organ-specific uptake of Cr-d3, significantly diminished growth with the exception of brain, progressive vacuolar myopathy, and markedly shortened lifespan.

Novel autophagic vacuolar myopathies: Phenotype and genotype features.

Autophagic vacuolar myopathies (AVMs) are an emerging group of heterogeneous myopathies sharing histopathological features on muscle pathology, in which autophagic vacuoles are the pathognomonic morphologic hallmarks. Glycogen storage disease type II (GSDII) caused by lysosomal acid α-glucosidase (GAA) deficiency is the best-characterised AVM. This study aimed to investigate the mutational profiling of seven neuromuscular outpatients sharing clinical, myopathological and biochemical findings with AVMs. We applied a diagnostic protocol, recently published by our research group for suspected late-onset GSDII (LO-GSDII), including counting PAS-positive lymphocytes on blood smears, dried blood spot (DBS)-GAA, muscle biopsy histological and immunofluorescence studies, GAA activity assay and expression studies on muscle homogenate, GAA sequencing, GAA multiplex ligation-dependent probe amplification (MLPA) and whole exome sequencing (WES). The patients had a limb girdle-like muscular pattern with persistent hyperCKaemia; vacuolated PAS-positive lymphocytes, glycogen accumulation and impaired autophagy at muscle biopsy. Decreased GAA activity was also measured. While GAA sequencing identified no pathogenic mutations, WES approach allowed us to identify for each patient an unexpected mutational pattern in genes cooperating in lysosomal-autophagic machinery, some of which have never been linked to human diseases. Our data suggest that reduced GAA activity may occur in any condition of impaired autophagy and that WES approach is advisable in all genetically undefined cases of autophagic myopathy. Therefore, deficiency of GAA activity and PAS-positive lymphocytes should be considered as AVM markers together with LC3/p62-positive autophagic vacuoles.

Cardiomyopathy phenotyping and risk-stratification in danon disease

Abstract Background Danon Disease (DD) is a rare, X-linked vacuolar myopathy due to mutations in Lysosomal Associated Membrane Protein 2 (LAMP-2). Though it is strongly associated with severe cardiomyopathy, heart failure and sudden death, there is no data on typical cardiac magnetic resonance (CMR) imaging characteristics in DD and their association with clinical severity and outcome. Purpose To phenotype and risk-stratify DD patients. Methods CMR scans of confirmed DD patients recruited in a global registry were prospectively analyzed for biventricular volumes, ejection fraction (EF), left ventricular (LV) strain, mass (LVM) and late gadolinium enhancement (LGE) in a core-lab blinded fashion. A major adverse cardiac event (MACE) was a composite of death, heart transplant and implantable cardioverter defibrillator (ICD) for secondary prevention. Results 12 DD patients (5 males [42%], median age 13 yrs [interquartile range (IQR) 5]) were included. LV hypertrophy (LVH) was present in 10/12 (83%), associated with LV dilation in 2 females. LVH was typically asymmetric in females (5/7) and concentric in males (3/5); right ventricular (RV) hypertrophy frequent in females (4/7). LV strain was reduced (global circumferential strain [GCS] −12±4%) and LGE common (73%), often extensive and always sparing the basal-mid septum. LGE was strongly associated with heart failure (BNP r=0.9, p=0.0021). Patients with MACE (6 [50%], median follow-up 2.9 yrs) had elevated LVM (241±63 g, p=0.032), impaired LV strain (GCS: −9.8±3.9, p=0.02) and higher LGE mass (median 56 g [IQR 35], p=0.021) compared to those without events during follow-up (LVM 155±56 g, GCS −14.9±1.6, LGE mass 0 g [IQR 8]). CMR characteristics were predictors of MACE (LV strain: hazard ratio [HR] 1.4, p=0.021; LGE mass: HR 1.1, p=0.03). Conclusions LGE sparing the basal-mid septum was pathognomonic in DD. LVH with reduced LV strain was the most common DD phenotype but the spectrum included LV dilation and RV hypertrophy in females. CMR characteristics (LV strain and LGE) were associated with heart failure and predicted worse outcome (heart transplant and fatal arrhythmias). CMR phenotyping and risk-stratification of this severe and underrecognized cardiomyopathy may aid diagnosis and clinical management in DD patients who need selection for early heart transplant, ICD implantation and targeted gene therapy. Danon Disease Phenotypes and Outcome Funding Acknowledgement Type of funding source: Other. Main funding source(s): National Institute of Health and Rocket Pharmaceuticals

AUTOPHAGIC MYOPATHIES / MYOFIBRILLAR MYOPATHIES / DISTAL MYOPATHIES / POMPE DISEASE: P.14 Autophagic vacuolar myopathy with autophagic vacuoles with sarcolemmal features (AVSF myopathy) including Danon disease and XMEA: A new clinical entity

A subgroup of autophagic vacuolar myopathies (AVMs) is characterized by unusual autophagic vacuoles with sarcolemmal features (AVSFs) and includes Danon disease and X-linked myopathy with excessive autophagy (XMEA). We suggest referring to this subgroup as ‘AVSF myopathy’ as a new clinical entity. However, the features of AVSF myopathy have not been well established. Therefore, to evaluate the clinical features, we reviewed the clinical histories, muscle specimens, and genetic analyses of Japanese patients with AVSF myopathy. In addition, to address the diagnostic importance of AVSFs, we studied AVSF myopathy and other AVMs (Pompe disease and rimmed vacuolar myopathies) pathologically. We identified 39 patients with Danon disease (17 males and 22 females) from 20 families with LAMP-2 mutations, 12 XMEA male patients from 4 families with VMA21 mutations, one male patient with adult-onset AVM with multiorgan involvement, and one asymptomatic female patient. Cardiomyopathy was evident in all patients with Danon disease. Among the 20 patients who died, 19 (95%) died of cardiac failure. Cardiomyopathy was not evident in all patients with XMEA. Among the 9 patients who died, all died of respiratory failure. Pathologically, AVSFs expressed virtually all sarcolemmal proteins in addition to AChE on their vacuolar membranes in all patients with AVSF myopathy. Multilayering of the basal lamina along vacuolar membranes was present in XMEA, adult type and asymptomatic type. This unique intracytoplasmic membrane structure was not found in other AVMs. AVSFs are autolysosomes surrounded by secondarily generated intracytoplasmic sarcolemma-like structures and delineate AVSF myopathy. In conclusion, AVSF myopathy is a very rare muscular disorder and may be primarily caused by lysosomal dysfunctions in consideration of both genetically diagnosable Danon disease and XMEA. Our findings suggest that AVSF myopathy may include more clinical phenotypes apart from Danon disease and XMEA.

MYASTHENIA & RELATED DISORDERS: P.37 Autophagy affected in patients with hypokalemic periodic paralysis

Hypokalemic periodic paralysis (hypoPP) is an autosomal dominant rare disorder that is caused by mutations in the genes for voltage gated calcium channel CaV1.1 (CACNA1S) and NaV1.4 (SCN4A). Patients with hypoPP may suffer from periodic paralysis alone, periodic paralysis with weakness or permanent weakness. HypoPP has been known to be associated with vacuolar myopathy for decades but the cause of this has not been known. We have investigated a cohort of 14 hypoPP patients with the R528H mutation in the CACNA1S gene for vacuoles and their content. The R528H mutation has previously been demonstrated to cause a Ca2+ leak through CaV1.1 into the cytoplasm, possibly causing disturbance in the calcium homeostasis. Histology and transmission electron microscopy revealed that vacuoles had a very heterogenous content of glycogen, fibrils and autophagosomes/endosomes. Further investigation demonstrated autophagosomes and endosomes were arrested in the autophagic processing pathway between the early and late stages of maturation, as well as large non-fused lysosomes. Expression analysis of proteins associated with endosomes, autophagosomes and lysosomes showed a significant decrease in levels of proteins involved in autophagy such as Rab5, Rab7, p62/SQSTM1, LC3I, Atg5 and LAMP1 in patients with hypoPP suggesting a systemic effect on the protein expression at the gene level, which decreased mRNA expression levels confirmed, possibly through a master regulator of autophagy gene expression. The findings suggest that changes in calcium homeostasis leads to disruptions in autophagic flux and abnormally large endosomes, autophagosomes and lysosomes that contribute to the vacuoles seen in patients with hypoPP.

Hereditary inclusion body myopathy: a clinical and genetic review

Introduction. Inclusion body myositis represents the most common acquired myopathy in clinical practice in patients over 50 years old. Despite classical approach to this myopathy as an inflammatory disorder, a muscle degenerative disorder is now considered the main mechanism linked to these vacuolar myopathies. Hereditary presentations, although quite rare, represent an expanding and underrecognized group in clinical practice. Objective. perform a structured review of the current literature regarding hereditary inclusion body myopathies. Method. review of U.S. NLM PubMed and MEDLINE database of original articles, case reports, case series and review articles including the terms “inclusion body myositis” OR “inclusion body myopathy” AND “genetics” OR “hereditary”. Results. We present in this article a wide review regarding the main clinical, imaging, pathophysiological, genetic and therapeutic aspects related to hereditary myopathies linked to seven different clinical and genetic presentations (GNE, MATR3, VCP, SQSTM1, MYH2, HNRNPA2B1 and HNRNPA1). Conclusion. Hereditary inclusion body myopathy is associated with at least 7 distinct clinic and genetic monogenic forms.

Differential diagnosis of vacuolar myopathies in the NGS era.

Altered autophagy accompanied by abnormal autophagic (rimmed) vacuoles detectable by light and electron microscopy is a common denominator of many familial and sporadic non‐inflammatory muscle diseases. Even in the era of next generation sequencing (NGS), late‐onset vacuolar myopathies remain a diagnostic challenge. We identified 32 adult vacuolar myopathy patients from 30 unrelated families, studied their clinical, histopathological and ultrastructural characteristics and performed genetic testing in index patients and relatives using Sanger sequencing and NGS including whole exome sequencing (WES). We established a molecular genetic diagnosis in 17 patients. Pathogenic mutations were found in genes typically linked to vacuolar myopathy (GNE, LDB3/ZASP, MYOT, DES and GAA), but also in genes not regularly associated with severely altered autophagy (FKRP, DYSF, CAV3, COL6A2, GYG1 and TRIM32) and in the digenic facioscapulohumeral muscular dystrophy 2. Characteristic histopathological features including distinct patterns of myofibrillar disarray and evidence of exocytosis proved to be helpful to distinguish causes of vacuolar myopathies. Biopsy validated the pathogenicity of the novel mutations p.(Phe55*) and p.(Arg216*) in GYG1 and of the p.(Leu156Pro) TRIM32 mutation combined with compound heterozygous deletion of exon 2 of TRIM32 and expanded the phenotype of Ala93Thr‐caveolinopathy and of limb‐girdle muscular dystrophy 2i caused by FKRP mutation. In 15 patients no causal variants were detected by Sanger sequencing and NGS panel analysis. In 12 of these cases, WES was performed, but did not yield any definite mutation or likely candidate gene. In one of these patients with a family history of muscle weakness, the vacuolar myopathy was eventually linked to chloroquine therapy. Our study illustrates the wide phenotypic and genotypic heterogeneity of vacuolar myopathies and validates the role of histopathology in assessing the pathogenicity of novel mutations detected by NGS. In a sizable portion of vacuolar myopathy cases, it remains to be shown whether the cause is hereditary or degenerative.

A Natural History Study of VCP Associated Vacuolar Myopathy in a Patient with the Common R155H Mutation

Background: IBMPFD (Inclusion Body Myopathy associated with Paget disease of the bone and Frontotemporal Dementia) is an autosomal dominant inherited disease caused by VCP gene mutations. Very little natural history data exists on this disease. We report a patient with a significant family history of IBMPFD associated with the common R155H mutation in the VCP gene. Objective: This study will address the lack of long-term data for muscle strength, and respiratory function in IBMPFD. The hypothesis is that detailed analysis in a single patient will provide meaningful natural history data in IBMPFD, a progressive neurodegenerative disease. Method: Regression analysis was performed across multiple parameters related to myopathy including dynamometry, MRC scale, IBM functional rating scale, pulmonary function studies and sleep quality. Results: Measurements of this patient highlight progressive generalized weakness in proximal and distal regions, decline in pulmonary function, and asymmetrical strength differences of the upper extremities. Measurements over five years revealed an overall deterioration with a slope of -1.13 and R2 value of 0.77. Conclusion: This unique data derived from long-term evaluations in a patient provides the first report of the rate of progression of muscle weakness and pulmonary function deterioration in VCP associated inclusion body myopathy.

Une cause rare d’altération de l’état général : cardiopathie et myopathie aux antipaludéens de synthèse

IntroductionThis case report signifies the need to systemically assess antimalarial toxicity in those undergoing long-term treatment. Case reportA 59-year-old man with a history of ischemic-labeled heart disease revealed by conduction disorders and cutaneous lupus treated initially with hydroxychloroquine followed by chloroquine consulted for asthenia and weight loss. Clinically, he had a muscular atrophy, a motor deficit, and an abolition of the osteo-tendinous reflexes in the lower limbs. Adverse drug effects of the antimalarial therapy were suspected–specifically, muscular and cardiac toxicity. The diagnosis was confirmed with a muscle biopsy, which showed typical and florid vacuolar myopathy. Cessation of the drug resulted in a slow regression of symptoms. ConclusionCardiac and muscular toxicity related to antimalarials are rare and sometimes fatal; thus, they must be systematically assessed in a patient with several years of exposure. A muscle biopsy could be sufficient to allow for the diagnosis.

A novel heterozygous mutation in the C-terminal region of HSPB8 leads to limb-girdle rimmed vacuolar myopathy (2727)

A novel heterozygous mutation in the C-terminal region of HSPB8 leads to limb-girdle rimmed vacuolar myopathy (2727)

Deep morphological analysis of muscle biopsies from type III glycogenesis (GSDIII), debranching enzyme deficiency, revealed stereotyped vacuolar myopathy and autophagy impairment

Glycogen storage disorder type III (GSDIII), or debranching enzyme (GDE) deficiency, is a rare metabolic disorder characterized by variable liver, cardiac, and skeletal muscle involvement. GSDIII manifests with liver symptoms in infancy and muscle involvement during early adulthood. Muscle biopsy is mainly performed in patients diagnosed in adulthood, as routine diagnosis relies on blood or liver GDE analysis, followed by AGL gene sequencing. The GSDIII mouse model recapitulate the clinical phenotype in humans, and a nearly full rescue of muscle function was observed in mice treated with the dual AAV vector expressing the GDE transgene.In order to characterize GSDIII muscle morphological spectrum and identify novel disease markers and pathways, we performed a large international multicentric morphological study on 30 muscle biopsies from GSDIII patients. Autophagy flux studies were performed in human muscle biopsies and muscles from GSDIII mice. The human muscle biopsies revealed a typical and constant vacuolar myopathy, characterized by multiple and variably sized vacuoles filled with PAS-positive material. Using electron microscopy, we confirmed the presence of large non-membrane bound sarcoplasmic deposits of normally structured glycogen as well as smaller rounded sac structures lined by a continuous double membrane containing only glycogen, corresponding to autophagosomes. A consistent SQSTM1/p62 decrease and beclin-1 increase in human muscle biopsies suggested an enhanced autophagy. Consistent with this, an increase in the lipidated form of LC3, LC3II was found in patients compared to controls. A decrease in SQSTM1/p62 was also found in the GSDIII mouse model.In conclusion, we characterized the morphological phenotype in GSDIII muscle and demonstrated dysfunctional autophagy in GSDIII human samples.These findings suggest that autophagic modulation combined with gene therapy might be considered as a novel treatment for GSDIII.