Priori, R, Conti, F, Luan, F L et al. · European journal of pediatrics · 1994 · DOI
This study describes four teenagers in Italy who developed severe, persistent fatigue after taking L-tryptophan supplements. Before the fatigue developed, they experienced eosinophilia myalgia syndrome (EMS)—a condition with high levels of certain white blood cells and severe muscle pain. The researchers found that these teenagers' symptoms looked very similar to chronic fatigue syndrome (ME/CFS).
This study is significant because it suggests that ME/CFS-like symptoms can develop as a consequence of specific environmental exposures and post-infectious/inflammatory states. Understanding these potential triggering pathways helps researchers identify possible mechanisms underlying ME/CFS and may inform patient histories and etiology investigations.
This case series does not establish a causal mechanism for how L-tryptophan or EMS leads to chronic fatigue, nor does it prove that all ME/CFS cases originate from similar triggers. The small number of cases (n=4) and lack of controls mean the findings cannot be generalized to broader populations or definitively distinguish this phenomenon from coincidental ME/CFS onset.
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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