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  • Physical training for McArdle disease.

    2 July 2018

    BACKGROUND: McArdle disease is a rare metabolic myopathy caused by a complete absence of the enzyme muscle glycogen phosphorylase. Affected people experience symptoms of fatigue and cramping within minutes of exercise and are at risk for acute muscle injury (rhabdomyolysis) and acute renal failure. If the first few minutes of exercise are paced, a 'second wind' will occur enabling exercise to continue. This is due to mobilisation and utilisation of alternative fuel substrates. Aerobic training appears to improve work capacity by increasing cardiovascular fitness. OBJECTIVES: To assess the effects of aerobic training in people with McArdle disease. SEARCH METHODS: We searched the Cochrane Neuromuscular Disease Group Specialized Register (11 January 2011), CENTRAL (2010, Issue 4), MEDLINE (January 1966 to January 2011) and EMBASE (January 1980 to January 2011). SELECTION CRITERIA: All randomised and quasi-randomised controlled studies of aerobic exercise training in people of all ages with McArdle disease. DATA COLLECTION AND ANALYSIS: Two authors identified possible studies for inclusion and assessed their methodological quality. Had more than one study of sufficient methodological quality been identified we would have undertaken a meta-analysis. MAIN RESULTS: There were no randomised or quasi-randomised controlled trials of aerobic training in people with McArdle disease. However, three open studies using small numbers of participants provided some evidence that aerobic training improves fitness without adverse events in people with McArdle disease. AUTHORS' CONCLUSIONS: Evidence from non-randomised studies using small numbers of patients suggest that it would be safe and worthwhile for larger controlled trials of aerobic training to be undertaken in people with McArdle disease.

  • The role of rituximab in the treatment of myasthenia gravis

    2 July 2018

    Rituximab, a chimaeric monoclonal antibody against CD20, depletes B cells. It was initially approved for the treatment of B-cell lymphomas, but more recently has been approved for use in rheumatoid arthritis. It has been used extensively 'off-label' for the treatment of other autoimmune diseases with some evidence of efficacy, but there remain some as yet unanswered concerns about safety. Myasthenia gravis is the paradigm of an antibody-mediated disorder, and B cells are believed to play a crucial role. This article reviews experience of the efficacy and safety of rituximab in myasthenia gravis and considers predictive factors for the success and failure of rituximab in this disease. © TOUCH BRIEFINGS 2010.

  • Reduced oxidative phosphorylation and proton efflux suggest reduced capillary blood supply in skeletal muscle of patients with dermatomyositis and polymyositis: A quantitative<sup>31</sup>P-magnetic resonance spectroscopy and MRI study

    2 July 2018

    Quantitative MRI and phosphorus magnetic resonance spectroscopy (31P-MRS) were used to investigate skeletal muscle metabolism in vivo in patients with dermatomyositis (DM) and polymyositis (PM) in order to evaluate the role of mitochondrial abnormalities in the pathogenesis and clinical expression of these conditions. Nine patients with DM (mean age ± SD, 57 ± 14 years) and five with PM (42 ± 12 years) and with age at disease onset 53 ± 16 and 38 ± 12 years, respectively, were included in the study together with 18 agematched controls. Post-exercise31P-MRS indices of muscle oxidative metabolism were all impaired in DM and PM. In both groups of patients, the phosphocreatine and adenosine diphosphate recovery half-times were almost twice as long as in controls (P < 0.05 for each variable) and the maximum rate of mitochondrial ATP production was half that found in normal subjects (P < 0.001). The rate of proton efflux from muscle fibres was significantly reduced in DM (P < 0.001) and PM (P = 0.02). The impairment of31P-MRS recovery indices in DM and PM patients was similar to that found in a group of 10 patients with a primary mitochondrial disorder that showed a normal proton efflux rate. There was no correlation between the MRS-detectable abnormalities and the degree of inflammation or fatty infiltration of the muscle, as measured by MRI. The in vivo findings in DM and PM patients indicate impaired muscle aerobic function, which, considering the reduced proton efflux, is likely to be secondary to an impaired blood supply. Our results suggest that the abnormal mitochondria seen in some muscle biopsies are unlikely to be the primary cause of the oxidative insufficiency in these patients.