Klein, R, Berg, P A · European journal of medical research · 1995
Researchers found that patients with ME/CFS and fibromyalgia syndrome (FMS) often have similar antibodies in their blood—proteins the immune system produces that may attack the body's own tissues. About 62% of ME/CFS patients and 73% of FMS patients had antibodies against serotonin, a chemical important for mood and pain regulation. Interestingly, these antibodies were also found in family members of affected patients, suggesting a genetic component may play a role.
This study provides immunological evidence that ME/CFS and FMS may share a common autoimmune mechanism involving antibodies against serotonin and neural antigens. If validated in larger studies, this could support recognition of these disorders as related autoimmune conditions and potentially guide targeted therapeutic approaches. The finding of familial antibody clustering also has implications for genetic screening and disease prevention in at-risk relatives.
This study does not prove that these antibodies cause ME/CFS or FMS symptoms, only that they are associated with these conditions. The cross-sectional design cannot establish causality or temporal relationships. Additionally, the presence of these antibodies in family members does not definitively prove genetic inheritance versus shared environmental exposure, and it remains unclear whether antibody positivity predicts disease development or severity.
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
Klein, R & Berg, P A (1995). High incidence of antibodies to 5-hydroxytryptamine, gangliosides and phospholipids in patients with chronic fatigue and fibromyalgia syndrome and their relatives: evidence for a clinical entity of both disorders.. European journal of medical research. https://pubmed.ncbi.nlm.nih.gov/9392689/
BibTeX
@article{mecfsatlas-klein-1995-high-incidence,
author = {Klein, R and Berg, P A},
title = {High incidence of antibodies to 5-hydroxytryptamine, gangliosides and phospholipids in patients with chronic fatigue and fibromyalgia syndrome and their relatives: evidence for a clinical entity of both disorders.},
journal = {European journal of medical research},
year = {1995},
note = {PubMed: 9392689},
url = {https://www.mecfsatlas.com/evidence/klein-1995-high-incidence},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/klein-1995-high-incidence
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