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Myastenia-Inflammatory Myopathy (MG-IM) association has been described in less than 50 cases, as isolated reports or in few case series. In most cases, MG and IM onset occur simultaneously even if the overlapping clinical manifestations could lead to delay the diagnosis in the early stage of disease. In these cases, thymic pathology is present in more than 50% of cases. Pathological findings can be consistent of polymyositis (63%), dermatomyositis (25%) or granulomatosis (12%). Accurate clinical manifestations and severity of IM in MG, including muscle specific antibodies (MSA) and muscle MRI, have not been systematically investigated and focal or mild subclinical myositis have not been reported. We observed that focal myositis or asymptomatic CK elevation can also occur in MG. In this review we have also retrospectively re-analyzed the clinical, serological, pathological and muscle imaging data from 13 patients with MG- IM from our cohort of 441 MG patients (2,9%). Clinical onset occurred simultaneously in 10/13 patients, whereas in 2 patients the IM appeared later in MG disease course (range 10-14 years) and conversely in 1 patient MG symptoms occurred later in IM disease course (4 years). Median age at disease onset was 51 year (range 24-73 years) regardless of clinical onset (MG or IM). Median clinical follow-up was 88 months (range 31-237 months). IM was suspected by CK elevation in all patients (ranging 800-3000 UI/L at first detection) and non-fatigable muscle weakness unresponsive to acetylcholinesterase inhibitors. All the patients presented mild to moderate MG symptoms. Three main categories of muscle involvement, sometimes overlapping, were recognizable: distal, proximal and subclinical myositits, leading to three main clinical groups (A,B,C) and two overlapping subgroups (A/B and B/C). Thymus pathology was present in 10/13 patients. Anti-AChR was detected in al all patients associated with anti-Titin and -RyR1 in those patients with thymoma. No MSA, nor MAA antibodies were detected. Muscle biopsy confirmed IM in all patients. In conclusion we redefined the clinical spectrum of muscle involvement in MG-IM association, which represent a continuum among 3 main clinical groups: distal, proximal and subclinical muscle involvement. Minimal muscle involvement and focal myositis could be underestimated among myasthenic patients and early aggressive immunotherapy could be required in focal group., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Introduction: Aquaporins (AQPs) are a family of transmembrane proteins involved in the maintenance of osmotic gradients. AQP4 is abundant in skeletal muscle, where it seems to be associated with glycolytic metabolism. We investigated the pattern of expression of AQP4 in normal human myofibers relative to the main forms of myosin heavy chain (MHC)., Methods: Six normal human muscle biopsies were analyzed by double immunofluorescence for co-expression of AQP4 and slow or fast MHC., Results: A high percentage (64-99%) of MHC-fast positive fibers showed immunoreaction for AQP4. Immunoreactivity for AQP4 was also present in MHC-slow positive fibers, but with a higher variability (5-72%) among biopsies., Discussion: The expression pattern of AQP4 in human myofibers is highly variable among different patients and cannot be predicted for single fibers depending on MHC type expression. Other factors, possibly related to muscle activity, may modulate AQP4 expression. Muscle Nerve 57: 856-859, 2018., (© 2017 Wiley Periodicals, Inc.)

We present three members of an Italian family affected by tubular aggregate myopathy (TAM) and congenital miosis harboring a novel missense mutation in ORAI1. All patients had a mild, late onset TAM revealed by asymptomatic creatine kinase (CK) elevation and congenital miosis consistent with a Stormorken-like Syndrome, in the absence of thrombocytopathy. Muscle biopsies showed classical histological findings but ultrastructural analysis revealed atypical tubular aggregates (TAs). The whole body muscle magnetic resonance imaging (MRI) showed a similar pattern of muscle involvement that correlated with clinical severity. The lower limbs were more severely affected than the scapular girdle, and thighs were more affected than legs. Molecular analysis revealed a novel c.290C>G (p.S97C) mutation in ORAI1 in all affected patients. Functional assays in both human embryonic kidney (HEK) cells and myotubes showed an increased rate of Ca 2+ entry due to a constitutive activation of the CRAC channel, consistent with a 'gain-of-function' mutation. In conclusion, we describe an Italian family harboring a novel heterozygous c.290C>G (p.S97C) mutation in ORAI1 causing a mild- and late-onset TAM and congenital miosis via constitutive activation of the CRAC channel. Our findings extend the clinical and genetic spectrum of the ORAI1-related TAM., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Tubular aggregate myopathy (TAM) is a heritable myopathy primarily characterized by progressive muscle weakness, elevated levels of creatine kinase (CK), hypocalcemia, exercise intolerance, and the presence of tubular aggregates (TAs). Here, we generated a knock-in mouse model based on a human gain-of-function mutation which results in a severe, early-onset form of TAM, by inducing a glycine-to-serine point mutation in the ORAI1 pore (Orai1 G100S/+ or GS mice). By 8 months of age, GS mice exhibited significant muscle weakness, exercise intolerance, elevated CK levels, hypocalcemia, and robust TA presence. Unexpectedly, constitutive Ca 2+ entry in mutant mice was observed in muscle only during early development and was abolished in adult skeletal muscle, partly due to reduced ORAI1 expression. Consistent with proteomic results, significant mitochondrial damage and dysfunction was observed in skeletal muscle of GS mice. Thus, GS mice represent a powerful model for investigation of the pathophysiological mechanisms that underlie key TAM symptoms, as well as those compensatory responses that limit the damaging effects of uncontrolled ORAI1-mediated Ca 2+ influx., (© 2024. The Author(s).)

The co-occurrence of genetic myopathies with myasthenia gravis (MG) is extremely rare, however a few studies have been reported. We aim to explore the link between genetically inherited muscle disorders and immune-mediated neuromuscular junction conditions, taking into account the diagnostic and therapeutic implications posed by these combined conditions. We searched all English medical papers registered in Web of Knowledge, PubMed, Google Scholar, and Science Direct between January 1987 concerning the association between muscular dystrophies (MD) and MG, also adding three new cases to the series reported so far. Three new clinical cases in which MG concurs with oculopharyngeal muscular dystrophy (OPMD) or facioscapulohumeral muscular dystrophy (FSHD) or myotonic dystrophy type 2 (DM2) were reported. A comprehensive literature review showed that FSHD is the dystrophy most frequently associated with generalized MG. The AChR antibody titer is high and neurophysiologic tests prove to be an essential tool for the diagnosis. The association between MG and MD is rare but should not be underestimated. The presence of unusual clinical features suggest investigating additional overlapping condition, especially when a treatable disease like MG is suspected., (© 2024. Fondazione Società Italiana di Neurologia.)