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 →
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
Priori, R, Conti, F, Luan, F L, Arpino, C, & Valesini, G (1994). Chronic fatigue: a peculiar evolution of eosinophilia myalgia syndrome following treatment with L-tryptophan in four Italian adolescents.. European journal of pediatrics. https://doi.org/10.1007/BF01956416
BibTeX
@article{mecfsatlas-priori-1994-chronic-fatigue,
author = {Priori, R and Conti, F and Luan, F L and Arpino, C and Valesini, G},
title = {Chronic fatigue: a peculiar evolution of eosinophilia myalgia syndrome following treatment with L-tryptophan in four Italian adolescents.},
journal = {European journal of pediatrics},
year = {1994},
doi = {10.1007/BF01956416},
note = {PubMed: 8033924},
url = {https://www.mecfsatlas.com/evidence/priori-1994-chronic-fatigue},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/priori-1994-chronic-fatigue
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