Meta-analyses uncover the genetic architecture of Idiopathic Inflammatory Myopathies.

Objective: Idiopathic inflammatory myopathies (myositis, IIMs) are rare, systemic autoimmune disorders that lead to muscle inflammation, weakness, and extra-muscular manifestations, with a strong genetic component influencing disease development and progression. Previous genome-wide association studies identified loci associated with IIMs. In this study, we imputed data from two prior genome-wide myositis studies and analyzed the largest myositis dataset to date to identify novel risk loci and susceptibility genes associated with IIMs and its clinical subtypes.

Autoantibodies against a subunit of mitochondrial respiratory chain complex I in inclusion body myositis.

Background: Autoantibodies are found in up to 80 % of patients with idiopathic inflammatory myopathies (IIM) and are associated with distinct clinical phenotypes. Autoantibodies targeting cytosolic 5'-nucleotidase 1A (anti-NT5C1A) are currently the only known serum biomarker for the subgroup inclusion body myositis (IBM), although detected even in other autoimmune diseases. The aim of the study was to identify new autoimmune targets in IIM.

Subcutaneous efgartigimod PH20 in generalized myasthenia gravis: A phase 3 randomized noninferiority study (ADAPT-SC) and interim analyses of a long-term open-label extension study (ADAPT-SC+).

ADAPT-SC (NCT04735432) was designed to evaluate noninferiority of subcutaneous (SC) efgartigimod PH20 to intravenous (IV) efgartigimod in participants with generalized myasthenia gravis (gMG). ADAPT-SC+ (NCT04818671) is an open-label extension study designed to assess long-term safety, tolerability, and efficacy of efgartigimod PH20 SC. Adult participants in ADAPT-SC were randomly assigned to receive a treatment cycle of 4 once-weekly administrations of efgartigimod PH20 SC 1000 ​mg or efgartigimod IV 10 ​mg/kg, followed by 7 weeks of follow-up.

Retrospective Study Shows That Serum Levels of Chemokine CXCL10 and Cytokine GDF15 Support a Diagnosis of Sporadic Inclusion Body Myositis and Immune-Mediated Necrotizing Myopathy.

The implementation of novel blood-based biomarkers is desired to reduce the diagnostic delay and burden for myositis patients. In this retrospective study, the potential of C-X-C motif chemokine ligand 10 (CXCL10) and growth differentiation factor 15 (GDF15) was explored in an established patient cohort diagnosed with immune-mediated necrotizing myopathy (IMNM; n = 21), sporadic inclusion body myositis (IBM; n = 18), overlap myositis (OM; n = 3), dermatomyositis (DM; n = 2), and anti-synthetase syndrome (ASS; n = 1), comparing these results with healthy controls (n = 10) and patients with a hereditary neuromuscular disorder (n = 14). CXCL10 and GDF15 were quantified in sera with enzyme-linked immunosorbent assays and immunolocalized in skeletal muscle tissue.

Effect of efgartigimod on muscle group subdomains in participants with generalized myasthenia gravis: post hoc analyses of the phase 3 pivotal ADAPT study.

Background And Purpose: Generalized myasthenia gravis (gMG) is a rare, chronic, neuromuscular autoimmune disease mediated by pathogenic immunoglobulin G (IgG) autoantibodies. Patients with gMG experience debilitating muscle weakness, resulting in impaired mobility, speech, swallowing, vision and respiratory function. Efgartigimod is a human IgG1 antibody Fc fragment engineered for increased binding affinity to neonatal Fc receptor.

Autosomal dominant in cis D4Z4 repeat array duplication alleles in facioscapulohumeral dystrophy.

Facioscapulohumeral dystrophy (FSHD) has a unique genetic aetiology resulting in partial chromatin relaxation of the D4Z4 macrosatellite repeat array on 4qter. This D4Z4 chromatin relaxation facilitates inappropriate expression of the transcription factor DUX4 in skeletal muscle. DUX4 is encoded by a retrogene that is embedded within the distal region of the D4Z4 repeat array.

Comparison of clinical features between patients with anti-synthetase syndrome and dermatomyositis: results from the MYONET registry.

Objectives: To compare clinical characteristics, including the frequency of cutaneous, extramuscular manifestations and malignancy, between adults with anti-synthetase syndrome (ASyS) and DM.

Methods: Using data regarding adults from the MYONET registry, a cohort of DM patients with anti-Mi2/-TIF1γ/-NXP2/-SAE/-MDA5 autoantibodies, and a cohort of ASyS patients with anti-tRNA synthetase autoantibodies (anti-Jo1/-PL7/-PL12/-OJ/-EJ/-Zo/-KS) were identified. Patients with DM sine dermatitis or with discordant dual autoantibody specificities were excluded.

Clinical Classification of Variants in the Valosin-Containing Protein Gene Associated With Multisystem Proteinopathy.

Background And Objectives: Pathogenic variants in the valosin-containing protein () gene cause a phenotypically heterogeneous disorder that includes myopathy, motor neuron disease, Paget disease of the bone, frontotemporal dementia, and parkinsonism termed multisystem proteinopathy. This hallmark pleiotropy makes the classification of novel variants challenging. This retrospective study describes and assesses the effect of 19 novel or nonpreviously clinically characterized variants identified in 28 patients (26 unrelated families) in the retrospective VCP International Multicenter Study.

C-terminal frameshift variant of TDP-43 with pronounced aggregation-propensity causes rimmed vacuole myopathy but not ALS/FTD.

Neuronal TDP-43-positive inclusions are neuropathological hallmark lesions in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Pathogenic missense variants in TARDBP, the gene encoding TDP-43, can cause ALS and cluster in the C-terminal prion-like domain (PrLD), where they modulate the liquid condensation and aggregation properties of the protein. TDP-43-positive inclusions are also found in rimmed vacuole myopathies, including sporadic inclusion body myositis, but myopathy-causing TDP-43 variants have not been reported.

Anoctamin-5 related muscle disease: clinical and genetic findings in a large European cohort.

Anoctamin-5 related muscle disease is caused by biallelic pathogenic variants in the anoctamin-5 gene (ANO5) and shows variable clinical phenotypes: limb-girdle muscular dystrophy type 12 (LGMD-R12), distal muscular dystrophy type 3 (MMD3), pseudometabolic myopathy or asymptomatic hyperCKaemia. In this retrospective, observational, multicentre study we gathered a large European cohort of patients with ANO5-related muscle disease to study the clinical and genetic spectrum and genotype-phenotype correlations. We included 234 patients from 212 different families, contributed by 15 centres from 11 European countries.

A retrospective survey of patients with hereditary transthyretin-mediated (hATTR) amyloidosis treated with patisiran in real-world clinical practice in Belgium.

Introduction: Hereditary transthyretin-mediated (hATTR) amyloidosis, a genetic disease caused by mutations in the transthyretin gene, leads to progressive sensory and autonomic neuropathy and/or cardiomyopathy and is associated with renal and ophthalmologic manifestations and a poor prognosis.

Methods: This is a retrospective study based on data collected from the medical records of patients with hATTR amyloidosis treated with patisiran between 01 July 2018 and 01 February 2021. Six Belgian neuromuscular reference centers participated, covering all patisiran-treated hATTR amyloidosis patients at the study time.

Risk of malignant hyperthermia in patients carrying a variant in the skeletal muscle ryanodine receptor 1 gene.

Malignant hyperthermia is a life-threatening disorder, which can be prevented by avoiding certain anesthetic agents. Pathogenic variants in the skeletal muscle ryanodine receptor 1-gene are linked to malignant hyperthermia. We retrospectively studied 15 patients who presented to our clinic with symptoms of muscle dysfunction (weakness, myalgia or cramps) and were later found to have a variant in the skeletal muscle ryanodine receptor 1-gene.

Inducible Heat Shock Protein 70 Levels in Patients and the mdx Mouse Affirm Regulation during Skeletal Muscle Regeneration in Muscular Dystrophy.

Background: Stress-inducible heat shock protein 70 (HSP70) is both a protective chaperone involved in protein homeostasis and an immune regulator. In both capacities, HSP70 has been implicated in muscle disorders, yet with fragmented and differing results. In this study we aimed to compare results obtained in the mouse model for the severest form of muscular dystrophy (MD) equivalent to Duchenne MD, termed the mdx mouse, with results obtained in human MD.

Exploring the Therapeutic Potential of Ectoine in Duchenne Muscular Dystrophy: Comparison with Taurine, a Supplement with Known Beneficial Effects in the Mouse.

Duchenne Muscular Dystrophy (DMD) is a debilitating muscle disorder that condemns patients to year-long dependency on glucocorticoids. Chronic glucocorticoid use elicits many unfavourable side-effects without offering satisfying clinical improvement, thus, the search for alternative treatments to alleviate muscle inflammation persists. Taurine, an osmolyte with anti-inflammatory effects, mitigated pathological features in the mouse model for DMD but interfered with murine development.

Prospective Natural History Study in 24 Adult Patients With LGMDR12 Over 2 Years of Follow-up: Quantitative MRI and Clinical Outcome Measures.

Background And Objectives: Limb-girdle muscular dystrophy autosomal recessive type 12 (LGMDR12) is a rare hereditary muscular dystrophy for which outcome measures are currently lacking. We evaluated quantitative MRI and clinical outcome measures to track disease progression to determine which tests could be useful in future clinical trials to evaluate potential therapies.

Methods: We prospectively measured the following outcome measures in all participants at baseline and after 1 and 2 years: 6-minute walk distance (6MWD), 10-meter walk test (10MWT), the Medical Research Council (MRC) sum scores, Biodex isometric dynamometry, serum creatine kinase, and 6-point Dixon MRI of the thighs.

Unraveling the Molecular Basis of the Dystrophic Process in Limb-Girdle Muscular Dystrophy LGMD-R12 by Differential Gene Expression Profiles in Diseased and Healthy Muscles.

Limb-girdle muscular dystrophy R12 (LGMD-R12) is caused by two mutations in anoctamin-5 (). Our aim was to identify genes and pathways that underlie LGMD-R12 and explain differences in the molecular predisposition and susceptibility between three thigh muscles that are severely (semimembranosus), moderately (vastus lateralis) or mildly (rectus femoris) affected in this disease. We performed transcriptomics on these three muscles in 16 male LGMD-R12 patients and 15 age-matched male controls.

Advance care planning in amyotrophic lateral sclerosis (ALS): study protocol for a qualitative longitudinal study with persons with ALS and their family carers.

Introduction: Amyotrophic lateral sclerosis (ALS) is an incurable motor neuron degenerative disease that has rapid progression and is associated with cognitive impairment. For people with ALS (pALS) and their family carers, advance care planning (ACP) is beneficial, as it can lead to feelings of control/relief and refusal of unwanted treatments. However, evidence concerning the experiences and preferences regarding ACP of pALS and their family carers, especially when their symptoms progress, is scarce.

Description of Osmolyte Pathways in Maturing Mice Reveals Altered Levels of Taurine and Sodium/Myo-Inositol Co-Transporters.

Duchenne muscular dystrophy (DMD) is a genetic disorder characterized by progressive muscle degeneration. Osmotic stress participates to DMD pathology and altered levels of osmolyte pathway members have been reported. The goal of this study was to gain insight in osmoregulatory changes in the mouse model by examining the expression of osmolyte pathway members, including taurine transporter (TauT), sodium myo-inositol co-transporter (SMIT), betaine GABA transporter (BGT), and aldose reductase (AR) in the skeletal muscles and diaphragm of mice aged 4, 8, 12, and 26 weeks.

Expanding the TDP-43 Proteinopathy Pathway From Neurons to Muscle: Physiological and Pathophysiological Functions.

TAR DNA-binding protein 43, mostly referred to as TDP-43 (encoded by the gene) is strongly linked to the pathogenesis of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). From the identification of TDP-43 positive aggregates in the brains and spinal cords of ALS/FTD patients, to a genetic link between mutations and the development of TDP-43 pathology in ALS, there is strong evidence indicating that TDP-43 plays a pivotal role in the process of neuronal degeneration. What this role is, however, remains to be determined with evidence ranging from gain of toxic properties through the formation of cytotoxic aggregates, to an inability to perform its normal functions due to nuclear depletion.

An exploratory study of circulating cytokines and chemokines in patients with muscle disorders proposes CD40L and CCL5 represent general disease markers while CXCL10 differentiates between patients with an autoimmune myositis.

Discriminating an autoimmune myositis from other disorders and subtyping of patient groups within this heterogeneous group of conditions remain diagnostic challenges. In our study we explored the potential of cytokine and chemokine typing in patient sera as an addition to the expanding set of blood-accessible diagnostic biomarkers available today. We selected sets of ten patients within well-characterized disease groups representing healthy controls, and patients with hereditary muscular dystrophies, immune-mediated necrotizing myopathy (IMNM) and sporadic inclusion body myositis (IBM).