McArdle, A, McArdle, F, Jackson, M J et al. · Clinical science (London, England : 1979) · 1996 · DOI
Researchers wanted to test whether a virus called enterovirus might be hiding in the muscles of people with ME/CFS and causing the fatigue and pain. They took muscle samples from 34 patients and looked carefully for signs of enteroviral infection, but found none. However, they did find that muscle tissue showed signs of reduced activity, including lower levels of the building blocks that muscle cells need to function properly.
This study directly addressed a leading hypothesis about ME/CFS causation—that enteroviral infection of muscle cells could explain the characteristic fatigue and post-exertional malaise. The findings help refocus research by ruling out persistent enteroviral infection in muscle as a mechanism, while highlighting the importance of mitochondrial dysfunction and reduced activity in the condition.
This study does not prove that enterovirus plays no role in ME/CFS; it only shows that detectable viral RNA is not present in muscle tissue at the time of biopsy. The virus could have triggered the disease earlier without remaining in muscle, or could be present in other tissues not examined here. The finding of reduced mitochondrial function does not establish whether this is a cause or consequence of reduced physical activity.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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