Kwon, Ji-Soo, Chang, Euijin, Jang, Hyeon Mu et al. · The Korean journal of internal medicine · 2025 · DOI
After COVID-19, some people develop long-lasting symptoms like fatigue, brain fog, and difficulty exercising—a condition called long COVID or PASC. This study measured immune system markers (called cytokines) in the blood of 79 people and found that certain symptoms were linked to higher levels of specific immune proteins, suggesting the immune system may stay overactive in some long COVID patients.
This study helps identify biological mechanisms underlying long COVID symptoms, which may parallels to ME/CFS pathophysiology including post-exertional malaise and immune dysregulation. Understanding cytokine patterns could inform targeted therapeutic approaches and validate symptom heterogeneity as reflecting distinct but related immune pathways.
This study does not prove that cytokine elevation *causes* these symptoms—only that they occur together (correlation, not causation). It does not establish whether elevated cytokines are pathogenic, protective, or merely epiphenomenal. Additionally, findings are limited to the acute-to-subacute phase (1–6 months) and may not apply to chronic long COVID or ME/CFS patients.
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
Kwon, Ji-Soo, Chang, Euijin, Jang, Hyeon Mu, Kim, Ji Yeun, Kim, Woori, Son, Ju Yeon, et al. (2025). Cytokine profiles associated with persisting symptoms of post-acute sequelae of COVID-19.. The Korean journal of internal medicine. https://doi.org/10.3904/kjim.2024.217
BibTeX
@article{mecfsatlas-kwon-2025-cytokine-profiles,
author = {Kwon, Ji-Soo and Chang, Euijin and Jang, Hyeon Mu and Kim, Ji Yeun and Kim, Woori and Son, Ju Yeon and Cha, Junho and Jang, Choi Young and Bae, Seongman and Jung, Jiwon and Kim, Min Jae and Chong, Yong Pil and Lee, Sang-Oh and Choi, Sang-Ho and Kim, Yang Soo and Kim, Sung-Han},
title = {Cytokine profiles associated with persisting symptoms of post-acute sequelae of COVID-19.},
journal = {The Korean journal of internal medicine},
year = {2025},
doi = {10.3904/kjim.2024.217},
note = {PubMed: 40635493},
url = {https://www.mecfsatlas.com/evidence/kwon-2025-cytokine-profiles},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/kwon-2025-cytokine-profiles
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