Pyomyositis is a pyogenic infection of skeletal striated muscle, usually found in tropical areas, often in immunocompromised patients. We report a new observation of a nontropical Enterobacter pyomyositis occurring in an immunocompetent female in Tunisia. A 53-year-old patient presented with acute fever and intense myalgia in the right thigh. On clinical examination she had an altered general condition, a fever at 40°C and an important swelling of the lateral side of the right thigh. In biology, she had an inflammatory syndrome. Blood culture had identified Enterobacter. Muscle magnetic resonance imaging showed diffuse inflammatory involvement of the vastus lateralis muscle of the right quadriceps associated with edematous infiltration of subcutaneous fatty tissues. Diagnosis of pyomyositis was retained. Antibiotic therapy initially probabilistic and then adapted to the antibiogram was initiated with a favorable outcome. Although rare outside the tropics, the potential severity of pyomyositis encourages its better knowledge.

BACKGROUND: Myotonic dystrophy type 1 (DM1) is an autosomal dominant disease characterized by myotonia and progressive muscular weakness and atrophy. The aim of this study was to investigate the usefulness of longitudinal muscle MRI in detecting disease activity and progression in DM1, and to better characterize muscle edema, fat replacement and atrophy overtime.
METHODS: This is a prospective, observational, longitudinal study including 25 DM1 patients that performed at least two muscle MRIs. Demographic and genetic characteristics were recorded. Muscular Impairment Rating Scale (MIRS) and MRC score were performed within 3 months from MRIs at baseline (BL) and at follow-up (FU). We analysed 32 muscles of lower body (LB) and 17 muscles of upper body (UB) by T1 and STIR sequences. T1-, STIR- and atrophy scores and their variations were evaluated. Correlations between MRIs\' scores and demographic, clinical and genetic characteristics were analysed.
RESULTS: Eighty (80%) of patients showed fat replacement progression at FU. The median T1 score progression (ΔT1-score) was 1.3% per year in LB and 0.5% per year in UB. The rate of fat replacement progression was not homogenous, stratifying patients from non-progressors to fast progressors (> 3% ΔT1-score per year). Half of the STIR-positive muscles at BL showed T1-score progression at FU. Two patients with normal MRI at baseline only showed STIR-positive muscle at FU, marking the disease activity onset. STIR positivity at baseline correlated with fat replacement progression (ΔT1-score; p < 0.0001) and clinical worsening at FU (ΔMRC-score; p < 0.0001). Sixty-five (65%) of patients showed STIR- and fat replacement-independent muscle atrophy progression, more evident in UB.
CONCLUSIONS: Muscle MRI represents a sensitive biomarker of disease activity, severity, and progression in DM1. STIR alterations precede fat replacement and identify patients with a higher risk of disease progression, while T1-sequences reveal atrophy and fat replacement progression before clinical worsening.

Introduction   VMA21 -related myopathy is one of the rare forms of slowly progressive myopathy observed in males. Till now, there have been only a handful of reports, mainly from Europe and America, and two reports from India. Method  Here, we describe a case of genetically confirmed VMA21 -associated myopathy with clinical, histopathological, and imaging features with a list of known VMA21 mutations. Results  A 29-year-old man had the onset of symptoms at 18 years of age with features of proximal lower limb weakness. Muscle magnetic resonance imaging showed the preferential involvement of vasti and adductor magnus. A biopsy of the left quadriceps femoris showed features of autophagic vacuolar myopathy with vacuoles containing granular eosinophilic materials. In targeted next-generation sequencing, hemizygous mutation in the 3\' splice site of intron 2 of the VMA21 gene (c.164-7 T > A) was identified and confirmed the diagnosis of X-linked myopathy with excessive autophagy. Conclusion  This report expands the phenotypic and genotypic profile of VMA21 -related myopathy, with a yet unreported mutation in India.

BACKGROUND: Magnetic resonance (MRI) imaging of the skeletal muscles (muscle MRI for short) is increasingly being used in clinical routine for diagnosis and longitudinal assessment of muscle disorders. However, cross-centre standards for measurement protocol and radiological assessment are still lacking.
OBJECTIVE: The aim of this expert recommendation is to present standards for the application and interpretation of muscle MRI in hereditary and inflammatory muscle disorders.
METHODS: This work was developed in collaboration between neurologists, neuroradiologists, radiologists, neuropaediatricians, neuroscientists and MR physicists from different university hospitals in Germany. The recommendations are based on expert knowledge and a focused literature search.
RESULTS: The indications for muscle MRI are explained, including the detection and monitoring of structural tissue changes and oedema in the muscle, as well as the identification of a suitable biopsy site. Recommendations for the examination procedure and selection of appropriate MRI sequences are given. Finally, steps for a structured radiological assessment are presented.
CONCLUSIONS: The present work provides concrete recommendations for the indication, implementation and interpretation of muscle MRI in muscle disorders. Furthermore, it provides a possible basis for the standardisation of the measurement protocols at all clinical centres in Germany.
UNASSIGNED: HINTERGRUND: Die Magnetresonanztomographie (MRT) der Skelettmuskulatur (kurz: Muskel-MRT) wird zunehmend routinemäßig zur Diagnose und Verlaufsbeurteilung von Muskelerkrankungen eingesetzt. Jedoch existierten bislang keine zentrumsübergreifenden Standards für Messprotokolle und die radiologische Befundung.
UNASSIGNED: In der vorliegenden Expertenempfehlung sollen Standards zur Anwendung und Befundinterpretation der Muskel-MRT bei angeborenen und entzündlichen Muskelerkrankungen vorgestellt werden.
METHODS: Diese Arbeit entstand in Zusammenarbeit von Neurologen, Neuroradiologen, Radiologen, Neuropädiatern, Neurowissenschaftlern sowie MR-Physikern verschiedener Universitätskliniken in Deutschland. Die Empfehlungen basieren auf Expertenwissen und einer gezielten Literaturrecherche.
UNASSIGNED: Es werden die Indikationen für eine Muskel-MRT erläutert. Diese beinhalten den Nachweis und die Verlaufskontrolle von strukturellen und ödematösen Veränderungen der Muskulatur sowie die Identifizierung einer geeigneten Biopsiestelle. Des Weiteren werden Empfehlungen zum Untersuchungsablauf und für geeignete MRT-Sequenzen gegeben. Zuletzt werden die Schritte für eine strukturierte radiologische Befunderhebung dargestellt.
UNASSIGNED: Die vorliegende Arbeit bietet konkrete Empfehlungen zur Indikationsstellung, Durchführung und Befundinterpretation der Muskel-MRT. Darüber hinaus stellt sie eine mögliche Grundlage zur Vereinheitlichung der Messprotokolle an allen klinischen Standorten in Deutschland dar.

BACKGROUND: Magnetic resonance (MRI) imaging of the skeletal muscles (muscle MRI for short) is increasingly being used in clinical routine for diagnosis and longitudinal assessment of muscle disorders. However, cross-centre standards for measurement protocol and radiological assessment are still lacking.
OBJECTIVE: The aim of this expert recommendation is to present standards for the application and interpretation of muscle MRI in hereditary and inflammatory muscle disorders.
METHODS: This work was developed in collaboration between neurologists, neuroradiologists, radiologists, neuropaediatricians, neuroscientists and MR physicists from different university hospitals in Germany. The recommendations are based on expert knowledge and a focused literature search.
RESULTS: The indications for muscle MRI are explained, including the detection and monitoring of structural tissue changes and oedema in the muscle, as well as the identification of a suitable biopsy site. Recommendations for the examination procedure and selection of appropriate MRI sequences are given. Finally, steps for a structured radiological assessment are presented.
CONCLUSIONS: The present work provides concrete recommendations for the indication, implementation and interpretation of muscle MRI in muscle disorders. Furthermore, it provides a possible basis for the standardisation of the measurement protocols at all clinical centres in Germany.
UNASSIGNED: HINTERGRUND: Die Magnetresonanztomographie (MRT) der Skelettmuskulatur (kurz: Muskel-MRT) wird zunehmend routinemäßig zur Diagnose und Verlaufsbeurteilung von Muskelerkrankungen eingesetzt. Jedoch existierten bislang keine zentrumsübergreifenden Standards für Messprotokolle und die radiologische Befundung.
UNASSIGNED: In der vorliegenden Expertenempfehlung sollen Standards zur Anwendung und Befundinterpretation der Muskel-MRT bei angeborenen und entzündlichen Muskelerkrankungen vorgestellt werden.
METHODS: Diese Arbeit entstand in Zusammenarbeit von Neurologen, Neuroradiologen, Radiologen, Neuropädiatern, Neurowissenschaftlern sowie MR-Physikern verschiedener Universitätskliniken in Deutschland. Die Empfehlungen basieren auf Expertenwissen und einer gezielten Literaturrecherche.
UNASSIGNED: Es werden die Indikationen für eine Muskel-MRT erläutert. Diese beinhalten den Nachweis und die Verlaufskontrolle von strukturellen und ödematösen Veränderungen der Muskulatur sowie die Identifizierung einer geeigneten Biopsiestelle. Des Weiteren werden Empfehlungen zum Untersuchungsablauf und für geeignete MRT-Sequenzen gegeben. Zuletzt werden die Schritte für eine strukturierte radiologische Befunderhebung dargestellt.
UNASSIGNED: Die vorliegende Arbeit bietet konkrete Empfehlungen zur Indikationsstellung, Durchführung und Befundinterpretation der Muskel-MRT. Darüber hinaus stellt sie eine mögliche Grundlage zur Vereinheitlichung der Messprotokolle an allen klinischen Standorten in Deutschland dar.

BACKGROUND: A few patients with inflammatory myopathy showed anti-mitochondrial antibody (AMA) positivity. This study aimed to report the clinical and pathological findings with vacuoles in 3 cases of such patients.
METHODS: Three cases with myositis from the Myositis Clinical Database of Peking University First Hospital were identified with AMA positivity. Their clinical records were retrospectively reviewed and the data was extracted. All the 3 cases underwent muscle biopsy.
RESULTS: Three middle-aged patients presented with chronic-onset weakness of proximal limbs, marked elevation of creatine kinase, and AMA-positivity. Two of the 3 cases meet the criteria of primary biliary cholangitis. All the 3 cases presented with cardiac involvement and proteinuria. Two cases developed type 2 respiratory failure. MRI of the thigh muscle showed multiple patches of edema bilaterally in both cases, mostly in the adductor magnus. Pathological findings include degeneration of muscle fibers, diffused MHC-I positivity, and complement deposits on cell membranes. Vacuoles without rims of different sizes were discovered under the membrane of the muscle fibers. A few RBFs were discovered in case 1, while a diffused proliferation of endomysium and perimysium was shown in case 2.
CONCLUSIONS: AMA-positive inflammatory myopathy is a disease that could affect multiple systems. Apart from inflammatory changes, the pathological findings of muscle can also present vacuoles.

OBJECTIVE: X-linked myopathy with excessive autophagy (XMEA) linked to the VMA21 gene leads to autophagy failure with progressive vacuolation and atrophy of skeletal muscles. Current knowledge of this rare disease is limited. Our objective was to define the clinical, radiological, and natural history of XMEA.
METHODS: We conducted a retrospective study collecting clinical, genetic, muscle imaging, and biopsy data of XMEA patients followed in France and reviewed the literature for additional cases.
RESULTS: Eighteen males had genetically confirmed XMEA in France, carrying four different VMA21 variants. Mean age at disease onset was 9.4 ± 9.9 (range 1-40) years. In 14/18 patients (77.8%), onset occurred during childhood (< 15 years); however in four patients, the disease started in adulthood. Patients had anterior and medial compartment thigh muscle weakness, distal contractures (56.3%), elevated CK levels (1287.9 ± 757.8 U/l) and autophagic vacuoles with sarcolemmal features on muscle histopathology. Muscle MRI (n = 10) showed a characteristic pattern of lower limb muscle involvement. In 11 patients, outcome measures were available for an average follow-up period of 10.6 ± 9.8 years and six of them show disease progression. Mean change of functional outcomes was 0.5 ± 1.2 points for Brooke and 2.2 ± 2.5 points for Vignos score, 7/16 patients (43.8%) needed a walking aid and 3/16 (18.8%) were wheelchair-bound (median age of 40 years old, range 39-48). The variant c.164-7 T > G was associated with a later onset of symptoms. Respiratory insufficiency was common (57.1%) but cardiac involvement rare (12.5%).
CONCLUSIONS: XMEA has variable age of onset, but a characteristic clinical, histopathological, and muscle imaging presentation, guiding the diagnosis. Although slowly, motor disability progresses with time, and relevant genotype-phenotype correlations will help design future clinical trials.

UNASSIGNED: This study aimed to assess the feasibility of a machine learning-based radiomics tools to discriminate between Limb-girdle muscular dystrophy R2 (LGMDR2) and immune-mediated necrotizing myopathy (IMNM) using lower-limb muscle magnetic resonance imaging (MRI) examination.
UNASSIGNED: After institutional review board approval, 30 patients with genetically proven LGMDR2 (12 females; age, 34.0 ± 11.3) and 45 patients with IMNM (28 females; age, 49.2 ± 16.6) who underwent lower-limb MRI examination including T1-weighted and interactive decomposition water and fat with echos asymmetric and least-squares estimation (IDEAL) sequences between July 2014 and August 2022 were included. Radiomics features of muscles were obtained, and four machine learning algorithms were conducted to select the optimal radiomics classifier for differential diagnosis. This selected algorithm was performed to construct the T1-weighted (TM), water-only (WM), or the combined model (CM) for calf-only, thigh-only, or the calf and thigh MR images, respectively. And their diagnostic performance was studied using area under the curve (AUC) and compared to the semi-quantitative model constructed by the modified Mercuri scale of calf and thigh muscles scored by two radiologists specialized in musculoskeletal imaging.
UNASSIGNED: The logistic regression (LR) model was the optimal radiomics model. The performance of the WM and CM for thigh-only images (AUC 0.893, 0.913) was better than those for calf-only images (AUC 0.846, 0.880) except the TM. For \"calf + thigh\" images, the TM, WM, and CM models always performed best (AUC 0.953, 0.907, 0.953) with excellent accuracy (92.0, 84.0, 88.0%). The AUCs of the Mercuri model of the calf, thigh, and \"calf + thigh\" images were 0.847, 0.900, and 0.953 with accuracy (84.0, 84.0, 88.0%).
UNASSIGNED: Machine learning-based radiomics models can differentiate LGMDR2 from IMNM, performing better than visual assessment. The model built by combining calf and thigh images presents excellent diagnostic efficiency.

Distal motor neuropathies (dHMN) are an heterogenous group of diseases characterized by progressive muscle weakness affecting predominantly the distal muscles of the lower and upper limbs. Our aim was to study the imaging features and pattern of muscle involvement in muscle magnetic resonance imaging (MRI) in dHMN patients of suspected genetic origin (dHMN). We conducted a retrospective study collecting clinical, genetic and muscle imaging data. Muscle MRI included T1-weighted and T2 weighted Short Tau Inversion Recovery images (STIR-T2w) sequences. Muscle replacement by fat was quantified using the Mercuri score. Identification of selective patterns of involvement was performed using hierarchical clustering. Eighty-four patients with diagnosis of dHMN were studied. Fat replacement was predominant in the distal lower leg muscles (82/84 cases), although also affected thigh and pelvis muscles. Asymmetric involvement was present in 29% of patients. The superficial posterior compartment of the leg, including the soleus and gastrocnemius muscles, was the most affected area (77/84). We observed a reticular pattern of fatty replacement progressing towards what is commonly known as \"muscle islands\" in 79.8%. Hyperintensities in STIR-T2w were observed in 78.6% patients mainly in distal leg muscles. Besides features common to all individuals, we identified and describe a pattern of muscle fat replacement characteristic of BICD2, HSPB1 and DYNC1H1 patients. We conclude that muscle MRI of patients with suspected dHMN reveals common features helpful in diagnosis process.

UNASSIGNED: Magnetic resonance imaging (MRI) is the dominant 3D imaging modality to quantify muscle properties in skeletal muscle disorders, in inherited and acquired muscle diseases, and in sarcopenia, in cachexia and frailty.
UNASSIGNED: This review covers T1 weighted and Dixon sequences, introduces T2 mapping, diffusion tensor imaging (DTI) and non-proton MRI. Technical concepts, strengths, limitations and translational aspects of these techniques are discussed in detail. Examples of clinical applications are outlined. For comparison 31P-and 13C-MR Spectroscopy are also addressed.
UNASSIGNED: MRI technology provides a rich toolset to assess muscle deterioration. In addition to classical measures such as muscle atrophy using T1 weighted imaging and fat infiltration using Dixon sequences, parameters characterizing inflammation from T2 maps, tissue sodium using non-proton MRI techniques or concentration or fiber architecture using diffusion tensor imaging may be useful for an even earlier diagnosis of the impairment of muscle quality.
UNASSIGNED: Quantitative MRI provides new options for muscle research and clinical applications. Current limitations that also impair its more widespread use in clinical trials are lack of standardization, ambiguity of image segmentation and analysis approaches, a multitude of outcome parameters without a clear strategy which ones to use and the lack of normal data.