Giloteaux, Ludovic, Hanson, Maureen R, Keller, Betsy A · The American journal of case reports · 2016 · DOI
This study compared two identical twins—one with ME/CFS and one without—to understand what causes the illness. The affected twin showed reduced exercise capacity, abnormal responses to physical exertion, and differences in immune markers and gut bacteria compared to the healthy twin. These findings suggest that ME/CFS involves problems with how the body responds to exercise and changes in the gut bacteria that may trigger inflammation.
By studying genetically identical twins with different ME/CFS status, researchers can isolate disease-specific factors from genetic background. This approach identified concrete physiological abnormalities—abnormal post-exercise immune activation and altered gut microbial composition—that may explain ME/CFS symptoms and could guide future biomarker development and therapeutic targets for the larger patient population.
This study does not prove that dysbiosis or altered immune activation *causes* ME/CFS, as this is a case report of two individuals rather than a causal study. The findings cannot be generalized to all ME/CFS patients without validation in larger cohorts. Additionally, it remains unclear whether the microbiome changes are a cause or consequence of ME/CFS.
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 →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Giloteaux, Ludovic, Hanson, Maureen R, & Keller, Betsy A (2016). A Pair of Identical Twins Discordant for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Differ in Physiological Parameters and Gut Microbiome Composition.. The American journal of case reports. https://doi.org/10.12659/ajcr.900314
BibTeX
@article{mecfsatlas-giloteaux-2016-pair-identical,
author = {Giloteaux, Ludovic and Hanson, Maureen R and Keller, Betsy A},
title = {A Pair of Identical Twins Discordant for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Differ in Physiological Parameters and Gut Microbiome Composition.},
journal = {The American journal of case reports},
year = {2016},
doi = {10.12659/ajcr.900314},
note = {PubMed: 27721367},
url = {https://www.mecfsatlas.com/evidence/giloteaux-2016-pair-identical},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/giloteaux-2016-pair-identical
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