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Metabolic Myopathy
Published in Maher Kurdi, Neuromuscular Pathology Made Easy, 2021
Metabolic myopathy is a diverse group of rare genetic disorders characterized by abnormal accumulation of proteins or metabolic products in muscle fibers. Impairments of glycolysis, glycogenolysis, fatty acid oxidation, or mitochondrial respiratory chains represent the majority of the accumulated products. These materials are aggregated in a group of vacuoles, referred to as vacuolar myopathy. The approach was explained in detail in Chapter 15.
Objections to the Russo–Williamson Thesis
Published in Donald Gillies, Causality, Probability, and Medicine, 2019
I will first give a brief discussion of McArdle disease, and then consider the evidence which led to the acceptance of the existence and cause of this disease. The disease is produced by a malfunctioning in the skeletal muscles (a metabolic myopathy). The normal functioning of skeletal muscles is shown, in a simplified form, in Figure 10.1.
Glycogenosis type II/Pompe/lysosomal α-glucosidase deficiency
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
The modern era of treatment was ushered in by the infusion of recombinant human α-glucosidase in three infants with infantile disease. There was a decrease in cardiac size and maintenance of normal function for more than one year at report [82]. Enzyme replacement therapy has been reported to be effective, especially in infants [83]. Enzyme replacement therapy was summarized in 40 patients with infantile-onset disease diagnosed between 1983 and 2008 in Taiwan [84]. There were five presymptomatic patients diagnosed by newborn screening. Regression of cardiomyopathy, lowering of B-type natriuretic peptide, and improved survival were recorded following treatment. Nevertheless, two died and two required ventilator support. Despite improvement in the electrocardiogram (EKG), three had life-threatening arrhythmias. None were in the newborn screening group. In the late-onset Pompe patients diagnosed by newborn screening [78], enzyme replacement therapy was initiated when symptoms or elevation of CK occurred. In a study of treatment in late-onset Pompe disease, 90 patients were randomized 2:1 to enzyme replacement or placebo [85]. Cardiovascular abnormalities were identified, such as elevated left ventricular mass, a short PR interval, or decreased left ventricular function in 5–10 percent. There was no change in cardiac status in response to enzyme replacement therapy. Among 90 patients randomized to enzyme replacement or placebo [86], there was no improvement in cardiac status. In assessment of the metabolic myopathy the six-minute walk test was used as a marker [87]. After 78 weeks of enzyme or placebo, there was significant improvement in walking distance, and stabilization of pulmonary function as measured by forced vital capacity (FVC). Mean increase in distance walked was 25 percent in the treatment group and 3% in the control. In mouse models, accumulation of glycogen in cervical spinal cord was great, indicating that therapy targeted to muscle maybe ineffective [88].
An update on diagnosis and therapy of metabolic myopathies
Published in Expert Review of Neurotherapeutics, 2018
Key clinical features of the history indicating metabolic myopathy are episodes of rhabdomyolysis, episodes of pigmenturia, exercise intolerance, and fatigue, symptoms arising after periods of prolonged fasting, prominent myalgias, cramps or stiffness, or consanguinity of the parents. Though rhabdomyolysis most commonly occurs in FAODs, it has been also reported in mitochondrial disorders [12] and GSDs [13]. Rhabdomyolysis may not only be characterized by pigmenturea, but may also manifest with headache, fever, vomiting, and malaise. Triggers of rhabdomyolysis include vigorous exercise, infections, drugs, toxins, fasting, surgery, or anesthesia [1]. Rhabdomyolysis may occur in episodic as well as in permanent metabolic myopathies.
SFN-SIQ, SFNSL and skin biopsy of 55 cases with small fibre involvement
Published in International Journal of Neuroscience, 2018
Bo Sun, Yifan Li, Lizhi Liu, Zhaohui Chen, Li Ling, Fei Yang, Jiexiao Liu, Hong Liu, Xusheng Huang
Skin biopsy is the single most reliable test in SFN diagnosis [1]. The 40 patients with an abnormal IENFD were subsequently diagnosed with PN accompanied by small fibre damage. IGT was the most prevalent neuropathy, which is consistent with previous research [18]. We conducted a thorough screen to determine the etiology of SFN. However, in some patients, no definite etiology was identified. These cases were regarded as idiopathic neuropathy. In general, approximately 50% of SFN cases are idiopathic [19]. The occurrence of SFN can precede the primary disease, and approximately 40%–50% of idiopathic SFN cases have been confirmed as IGT-related SFN [18,20–23]. Thus, routine follow-up should be performed for these patients to identify IGT. Furthermore, SFN is the only presentation of late-onset Fabry disease [24], which should be considered idiopathic SFN. Sodium channel Nav1.7, Nav1.8 and Nav1.9 mutations have been associated with idiopathic SFN [19,25]. However, genetic testing was not performed in the current study. Therefore, genetic mutations related to SFN cannot be excluded. Interestingly, in this study, we observed that one patient with lipid storage myopathy also presented with hyperalgesia. A research team at Duke University previously reported that SFN was prevalent in late-onset Pompe disease [11], which raises the possibility that patients with hereditary metabolic myopathy are susceptible to SFN. However, this potential relationship requires further research. Furthermore, that patient also exhibited hyperlipidemia. Evidence indicates that the elements of metabolic syndrome, including hyperlipidemia and obesity, are risk factors for SFN [26]; thus, metabolic-associated SFN cannot be ruled out. Another patient who exhibited thalamus cavernous haemangioma presented with pain in the lower limbs that was regarded as thalamus-related pain. Hsieh et al. [27] demonstrated that IENFD could be related to pain-associated brain regions in SFN.
Diagnostic challenges in metabolic myopathies
Published in Expert Review of Neurotherapeutics, 2020
Corrado Angelini, Roberta Marozzo, Valentina Pegoraro, Sabrina Sacconi
Once the diagnosis is suspected or reached, the follow-up of the metabolic myopathy is useful and treatment might be attempted. The experienced clinician will be able to share with colleagues the clinical signs, i.e., red flags, that are rarely recorded on charts and even shared with residents and fellows.