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Advances in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), 2nd Edition

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Pathology, Diagnostics, and Therapeutics".

Deadline for manuscript submissions: closed (20 March 2026) | Viewed by 31650

Special Issue Editor


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Guest Editor
Department of Microbiology and Immunology, Reno School of Medicine, University of Nevada, Reno, NV 89557, USA
Interests: gut-brain axis; neuroimmune disease; GI-associated plasmacytoid dendritic cells; Alzheimer’s disease; myalgic encephalomyelitis
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Special Issue Information

Dear Colleagues,

This Special Issue is a continuation of our previous Special Issue, “Advances of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)”.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is an illness of unknown etiology, characterized by multiple physical symptoms and comorbid conditions. Symptoms often reported by those with ME/CFS include unexplained fatigue that lasts for more than six months, post-exertional malaise, neurocognitive problems, unrefreshing sleep, and gastrointestinal issues. Clinical laboratory findings often include inflammatory sequelae, metabolic disturbances, self-reactive antibodies, and immune cell abnormalities. Although many who suffer from ME/CFS report that they developed the condition following a “flu-like” illness from which they never fully recovered, an etiological agent has not been reproducibly identified. Likewise, many individuals infected by the SARS-CoV-2 virus often never fully recover and present with symptoms that significantly overlap with those of ME/CFS. This syndrome is typically referred to as long COVID-19 or post-acute sequelae of SARS COV-2 infection. In this Special Issue, which addresses the advances in research regarding myalgic encephalomyelitis/chronic fatigue syndrome, we aim to publish original research papers and reviews that focus on the involvement of the immune system in ME/CFS. Reports that leverage commonalities between ME/CFS and long COVID-19 to identify the mechanisms behind immune abnormalities are highly encouraged.

Dr. Vincent C. Lombardi
Guest Editor

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Keywords

  • ME/CFS
  • PASC
  • long COVID-19
  • inflammation
  • innate immunity
  • adaptive immunity
  • mast cell activation
  • post-infection syndrome
  • metabolism
  • autoantibodies

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Published Papers (5 papers)

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Research

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30 pages, 3064 KB  
Article
Genetic Insights into Circulating Complement Proteins in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Potential Inflammatory Subgroup
by Jessica Maya, Elizabeth R. Unger, Jin-Mann S. Lin and Mangalathu S. Rajeevan
Int. J. Mol. Sci. 2026, 27(3), 1574; https://doi.org/10.3390/ijms27031574 - 5 Feb 2026
Viewed by 900
Abstract
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a debilitating multi-system illness with heterogeneity that complicates identifying the pathophysiology, biomarkers, and therapeutic targets. Evidence indicates the importance of immune dysregulation, including the complement system, in ME/CFS. This study investigates the contribution of genetic drivers to [...] Read more.
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a debilitating multi-system illness with heterogeneity that complicates identifying the pathophysiology, biomarkers, and therapeutic targets. Evidence indicates the importance of immune dysregulation, including the complement system, in ME/CFS. This study investigates the contribution of genetic drivers to potential dysregulation of the complement pathway in ME/CFS. We used protein quantitative trait loci (pQTL) analyses, adjusted for covariates using linear and logistic regression, to identify genetic variants significantly associated with plasma complement protein levels in a study sample identified from the general population (50 ME/CFS and 121 non-fatigued). ME/CFS patients carrying certain pQTLs exhibited dysregulation of the alternative complement pathway, which defined an inflammatory subgroup with a high C3/low Bb profile and established a genetic link to dysregulation of the alternative complement pathway. Six of the significant pQTLs were also associated with fatigue-related phenotypes in the UK Biobank, four of which were complement-associated, providing some validation in an independent population. Our findings highlight a mechanism by which risk alleles contribute to ME/CFS heterogeneity, providing evidence of a genetic basis for complement dysregulation in a subset of patients. This approach could identify pathway-focused subgroups in ME/CFS and related illnesses to inform personalized approaches to diagnosis and treatment. Full article
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12 pages, 3191 KB  
Article
Systems Modeling Reveals Shared Metabolic Dysregulation and Potential Treatments in ME/CFS and Long COVID
by Gong-Hua Li, Fei-Fei Han, Efthymios Kalafatis, Qing-Peng Kong and Wenzhong Xiao
Int. J. Mol. Sci. 2025, 26(13), 6082; https://doi.org/10.3390/ijms26136082 - 25 Jun 2025
Cited by 3 | Viewed by 11865
Abstract
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Long COVID are complex multisystem conditions that pose significant challenges in healthcare. Accumulated research evidence suggests that ME/CFS and Long COVID exhibit overlapping metabolic symptoms, indicating potential shared metabolic dysfunctions. This study aims to systematically explore shared [...] Read more.
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Long COVID are complex multisystem conditions that pose significant challenges in healthcare. Accumulated research evidence suggests that ME/CFS and Long COVID exhibit overlapping metabolic symptoms, indicating potential shared metabolic dysfunctions. This study aims to systematically explore shared metabolic disturbances in the muscle tissue of patients. Utilizing genome-wide metabolic modeling, we identified key metabolic irregularities in the muscle of patients with ME/CFS, notably the downregulation of the alanine and aspartate metabolism pathway and the arginine and proline metabolism pathway. Further, in silico knockout analyses suggested that supplementation with aspartate (ASP) or asparagine (ASN) could potentially ameliorate these metabolic deficiencies. In addition, assessments of metabolomic levels in Long COVID patients also showed the significant downregulation of ASP during post-exertional malaise (PEM) in both muscle and blood. Consequently, we propose that a combination of l-ornithine and l-aspartate (LOLA) is a potential candidate to alleviate metabolic symptoms in ME/CFS and Long COVID for future clinical trials. Full article
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Review

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20 pages, 1123 KB  
Review
Mucosal Viruses in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Missing Piece of the Puzzle?
by Krishani Dinali Perera, Paige Cameron, Tayyibah Sarwar and Simon R. Carding
Int. J. Mol. Sci. 2025, 26(22), 11161; https://doi.org/10.3390/ijms262211161 - 19 Nov 2025
Cited by 1 | Viewed by 4169
Abstract
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic condition without a definitive aetiology, no reliable diagnostic test, and no proven effective treatment. Despite most patients reporting a post-viral onset of illness, findings to date are conflicting on whether a single virus or [...] Read more.
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic condition without a definitive aetiology, no reliable diagnostic test, and no proven effective treatment. Despite most patients reporting a post-viral onset of illness, findings to date are conflicting on whether a single virus or multiple viral triggers are involved. Most studies to date have focused on detecting viruses in blood and circulating immune cells with relatively few investigating the presence of viruses in mucosal sites. In this review, we propose that this represents a critical gap in understanding the pathophysiology of ME/CFS knowledge, as mucosal tissues are primary entry points for most pathogens and often serve as reservoirs where viruses may persist. Consequently, they represent ideal niches for identifying persistent infections in ME/CFS. Emerging evidence from saliva and other mucosal samples in ME/CFS patients is consistent with this proposal and that latent viruses can persist and periodically reactivate in mucosal tissues from where they can potentially contribute to immune dysregulation, chronic inflammation, and increased symptom severity that defines ME/CFS. Full article
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18 pages, 278 KB  
Review
Biomarkers over Time: From Visual Contrast Sensitivity to Transcriptomics in Differentiating Chronic Inflammatory Response Syndrome and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome
by Ming Dooley
Int. J. Mol. Sci. 2025, 26(15), 7284; https://doi.org/10.3390/ijms26157284 - 28 Jul 2025
Viewed by 5277
Abstract
Chronic inflammatory response syndrome (CIRS) and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) are debilitating multisystem illnesses that share overlapping symptoms and molecular patterns, including immune dysregulation, mitochondrial impairment, and vascular dysfunction. This review provides a chronological synthesis of biomarker development in CIRS, tracing its [...] Read more.
Chronic inflammatory response syndrome (CIRS) and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) are debilitating multisystem illnesses that share overlapping symptoms and molecular patterns, including immune dysregulation, mitochondrial impairment, and vascular dysfunction. This review provides a chronological synthesis of biomarker development in CIRS, tracing its evolution from early functional tests such as visual contrast sensitivity (VCS) to advanced transcriptomic profiling. Drawing on peer-reviewed studies spanning two decades, we examine the layered integration of neuroendocrine, immunologic, metabolic, and genomic markers that collectively support a multisystem model of innate immune activation specific to environmentally acquired illness. Particular focus is given to the Gene Expression: Inflammation Explained (GENIE) platform’s use of transcriptomics to classify disease stages and distinguish CIRS from other fatiguing conditions. While ME/CFS research continues to explore overlapping pathophysiologic features, it has yet to establish a unified diagnostic model with validated biomarkers or exposure-linked mechanisms. As a result, many patients labeled with ME/CFS may, in fact, represent unrecognized CIRS cases. This review underscores the importance of structured biomarker timelines in improving differential diagnosis and guiding treatment in complex chronic illness and highlights the reproducibility of the CIRS framework in contrast to the diagnostic ambiguity surrounding ME/CFS. Full article

Other

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21 pages, 1903 KB  
Perspective
Glymphatic System Dysregulation as a Key Contributor to Myalgic Encephalomyelitis/Chronic Fatigue Syndrome
by Mohsen Nemat-Gorgani, Michael Anthony Jensen and Ronald Wayne Davis
Int. J. Mol. Sci. 2025, 26(23), 11524; https://doi.org/10.3390/ijms262311524 - 27 Nov 2025
Viewed by 7431
Abstract
Defined by the World Health Organization as a neurological disorder, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a disabling illness, affecting millions of people worldwide. First reported in the early nineteenth century, ME/CFS is uniquely characterized by a wide array of symptoms, including fatigue, [...] Read more.
Defined by the World Health Organization as a neurological disorder, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a disabling illness, affecting millions of people worldwide. First reported in the early nineteenth century, ME/CFS is uniquely characterized by a wide array of symptoms, including fatigue, brain fog, post-exertional malaise (PEM), sleep dysfunction, and orthostatic intolerance (OI). Despite decades of extensive research, there are no effective medical treatments or simple diagnostics for ME/CFS, with an estimated 90% of patients remaining undiagnosed. The recently discovered glymphatic system, a lymphatic analog of the brain, is believed to be responsible for the removal of toxic metabolic wastes accumulated in the course of daily activities, primarily during sleep. A link between glymphatic dysfunction and some neurological disorders such as Alzheimer’s disease has already been established, raising the possibility of its involvement in ME/CFS. Accordingly, we believe the ME/CFS medical/scientific community will be interested in seriously considering GD an important contributor to its pathophysiology. If so, therapeutics that modulate glymphatic function may also benefit patients with ME/CFS. Full article
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