Moezzi, Atefeh, Elremaly, Wesam, Leveau, Corinne et al. · International journal of molecular sciences · 2026 · DOI
This study observed that Long COVID patients with different versions of a protein called haptoglobin showed different patterns of cognitive problems after physical exertion. Patients carrying certain haptoglobin variants (Hp2) reported worse fatigue and cognitive decline following a challenge test, while those with the Hp1-1 variant showed better cognitive resilience. The findings are preliminary and come from a small group; larger studies are needed to confirm whether haptoglobin type could help identify which Long COVID patients are at higher risk for these cognitive changes.
Because of the documented clinical overlap between Long COVID and ME/CFS, this work may be relevant to understanding why ME/CFS patients vary in their response to exertion and cognitive symptoms. By analogy, haptoglobin phenotyping could, if validated, offer a biological marker to stratify ME/CFS patients into more homogeneous subgroups for research and potential personalized monitoring. However, direct applicability to ME/CFS remains to be established, as this study was conducted in a Long COVID cohort.
This study does not establish that haptoglobin phenotype causes post-exertional cognitive dysfunction, only that it is associated with differential patterns in a small Long COVID sample. It does not validate haptoglobin as a clinical biomarker—the authors themselves call for validation in larger independent cohorts. It does not demonstrate that the findings apply to ME/CFS; generalization from Long COVID to ME/CFS requires separate evidence. The small sample size (N=44 LC) and unknown peer-review status limit the strength of any conclusions.
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
Moezzi, Atefeh, Elremaly, Wesam, Leveau, Corinne, Franco, Anita, Nepotchatykh, Oleg, Armstrong, Christopher W, et al. (2026). Haptoglobin Phenotypes Stratify Post-Exertional Cognitive Dysfunction Associated with Altered Cerebral Oxygenation and Metabolic Signatures in Long COVID.. International journal of molecular sciences. https://doi.org/10.3390/ijms27157000
BibTeX
@article{mecfsatlas-moezzi-2026-haptoglobin-phenotypes,
author = {Moezzi, Atefeh and Elremaly, Wesam and Leveau, Corinne and Franco, Anita and Nepotchatykh, Oleg and Armstrong, Christopher W and Moreau, Alain},
title = {Haptoglobin Phenotypes Stratify Post-Exertional Cognitive Dysfunction Associated with Altered Cerebral Oxygenation and Metabolic Signatures in Long COVID.},
journal = {International journal of molecular sciences},
year = {2026},
doi = {10.3390/ijms27157000},
note = {PubMed: 42589652},
url = {https://www.mecfsatlas.com/evidence/moezzi-2026-haptoglobin-phenotypes},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-08-15. https://www.mecfsatlas.com/evidence/moezzi-2026-haptoglobin-phenotypes
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