Hajdarevic, Riad, Lande, Asgeir, Rekeland, Ingrid et al. · Brain, behavior, and immunity · 2021 · DOI
This study looked at genes related to the immune system in people with ME/CFS to understand why some people develop the condition. Researchers compared genetic markers in 427 Norwegian ME/CFS patients with 480 healthy controls and found two specific genetic regions associated with ME/CFS—one involving immune system genes that present antigens to cells, and another in a different immune region. These findings suggest the immune system's ability to recognize and respond to threats may play a role in ME/CFS.
This is one of the first studies to systematically identify specific genetic regions associated with ME/CFS susceptibility, providing evidence for an immune-mediated component of the disease. If replicated, these findings could lead to better understanding of disease mechanisms, improved diagnostic approaches, and potentially targeted treatments based on immune system biology.
This study does not prove that HLA variants cause ME/CFS—it demonstrates association only, not causation. The findings are specific to a Norwegian population and must be confirmed in other populations before broader conclusions can be drawn. The study also does not establish which genes in the identified regions are actually responsible for disease susceptibility, as multiple genes show associations.
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
Hajdarevic, Riad, Lande, Asgeir, Rekeland, Ingrid, Rydland, Anne, Strand, Elin B, Sosa, Daisy D, et al. (2021). Fine mapping of the major histocompatibility complex (MHC) in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) suggests involvement of both HLA class I and class II loci.. Brain, behavior, and immunity. https://doi.org/10.1016/j.bbi.2021.08.219
BibTeX
@article{mecfsatlas-hajdarevic-2021-fine-mapping,
author = {Hajdarevic, Riad and Lande, Asgeir and Rekeland, Ingrid and Rydland, Anne and Strand, Elin B and Sosa, Daisy D and Creary, Lisa E and Mella, Olav and Egeland, Torstein and Saugstad, Ola D and Fluge, Øystein and Lie, Benedicte A and Viken, Marte K},
title = {Fine mapping of the major histocompatibility complex (MHC) in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) suggests involvement of both HLA class I and class II loci.},
journal = {Brain, behavior, and immunity},
year = {2021},
doi = {10.1016/j.bbi.2021.08.219},
note = {PubMed: 34403736},
url = {https://www.mecfsatlas.com/evidence/hajdarevic-2021-fine-mapping},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/hajdarevic-2021-fine-mapping
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