Tag: letter

Authors’ Response to “Comment on ‘SMPDL3B as a novel biomarker and therapeutic target in myalgic encephalomyelitis’”

Letter:

We thank Chen and Yan for their thoughtful and positive comments on our recent publication and for their interest in the translational implications of SMPDL3B biology in myalgic encephalomyelitis (ME) [, ]. Their letter provides a welcome opportunity to clarify methodological points related to biomarker validation, in vitro pharmacological assays, and mechanistic interpretation []. We appreciate this constructive dialogue and address each issue below in a collegial and scientifically grounded manner.

Read the rest of this letter HERE>>

Source: Rostami-Afshari B, Elremaly W, Franco A, Moreau A. Authors’ Response to “Comment on ‘SMPDL3B as a novel biomarker and therapeutic target in myalgic encephalomyelitis'”. J Transl Med. 2026 Jan 16;24(1):75. doi: 10.1186/s12967-025-07583-z. PMID: 41546078; PMCID: PMC12809929. https://pmc.ncbi.nlm.nih.gov/articles/PMC12809929/ (Full text)

Wheat and chaff in Myalgic Encephalomyelitis/Chronic fatigue syndrome (ME/CFS) in clinics and laboratory

To the Editor,

We read the contribution by Hunter et al., titled “Development and validation of blood-based diagnostic biomarkers for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) using EpiSwitch® 3-dimensional genomic regulatory immuno-genetic profiling” in this journal, initially impressed for the large collection of data. They actually presented a novel, genome-wide epigenetic profiling approach using EpiSwitch® technology to identify potential diagnostic biomarkers for ME/CFS [1]. The use of 3D chromatin conformation signatures provides a fresh perspective on disease-specific gene regulation, moving beyond conventional transcriptomics and methylation analyses. In general, the diagnostic model demonstrates impressive sensitivity (92%) and specificity (98%) in distinguishing ME/CFS patients from controls, suggesting real clinical potential [1]. Moreover, the application of advanced machine learning techniques adds analytical robustness, while pathway analysis identifies biologically plausible immune-related mechanisms. This integrative approach sets a promising foundation for future biomarker-driven diagnostics and personalized therapy stratification in ME/CFS. Fundamentally, they presented a retrospective case-control analysis aiming to identify diagnostic epigenetic markers for ME/CFS using 3D chromatin conformation profiling (EpiSwitch®). However, while the authors make bold claims regarding diagnostic sensitivity and specificity, the paper suffers from multiple scientific weaknesses and methodological ambiguities that undermine its validity and translational relevance.

First, the article repeatedly asserts that “immune dysregulation” is a hallmark of ME/CFS, citing elevated pro-inflammatory cytokines and natural killer (NK) cell dysfunction. However, whereas the authors cite updated papers with a presumptive relationship with the issue, a critical omission here is the lack of citation of early foundational immunological studies in ME/CFS [2]. Notably absent is the 1994 work by Tirelli et al. in the Scandinavian Journal of Immunology, which documented, for the first time, immunological abnormalities in CFS patients and could serve as an important historical anchor for claims of immune dysregulation [2]. This omission raises concerns about reporting bias and selective citation to frame the narrative around newer, possibly more aligned findings with the current study methodology [2, 3].

Additionally, the paper refers to “ME/CFS inclusion criteria” as requiring severe CFS with patients being “housebound,” but fails to specify which diagnostic criteria were used, whether the Fukuda, Canadian Consensus, International Consensus, or IOM/NAM criteria [1]. This lack of precision is critical, as different case definitions yield different cohorts in terms of clinical features and biological signatures. Using “severe housebound” as a criterion, without reference to a validated clinical definition or stratification tool (e.g., Bell Disability Scale), introduces subjectivity and undermines the reproducibility of patient selection. The term “housebound” is not a recognized diagnostic stratifier and suggests imprecise cohort construction.

Further ambiguity arises when the authors discuss the control group. They state that controls had “none of the four key CFS symptoms present or in the past” and “preferably an existing history of glandular fever or COVID.” The phrase “preferably” is ambiguous and methodologically problematic [1]. Did the control group actually include individuals with prior infectious mononucleosis or COVID-19, and if so, how were these illnesses verified? The phrase “preferably” suggests either inconsistency in selection or retrospective rationalization, both of which compromise the clarity and control of variables in the study. Furthermore, it is scientifically incoherent to describe individuals as controls (i.e., free from ME/CFS) while also including those with a known post-infectious risk profile, potentially biasing the control group with latent post-viral immunogenetic changes [1].

There is further conceptual confusion when the authors state that the ME/CFS network reveals some overlap with pathways involved in multiple sclerosis (MS) and rheumatoid arthritis (RA). While such overlaps are plausible and worth exploring, the authors do not sufficiently explain the biological rationale for this claim or its relevance to ME/CFS pathophysiology [1]. They reference IL-2, IL-10, CD4, and TLR pathways as shared elements, but these are highly pleiotropic and non-specific immunological signals.

The mere presence of these markers in ME/CFS does not imply mechanistic similarity to MS or RA. Without longitudinal or functional studies, this comparison becomes speculative and possibly misleading, especially given the known heterogeneity of ME/CFS and the distinct immunopathology of autoimmune diseases like MS.

Read the rest of this letter HERE.

Source: Tirelli U, Franzini M, Chirumbolo S. Wheat and chaff in Myalgic Encephalomyelitis/Chronic fatigue syndrome (ME/CFS) in clinics and laboratory. J Transl Med. 2026 Jan 5;24(1):20. doi: 10.1186/s12967-025-07397-z. PMID: 41491817. https://link.springer.com/article/10.1186/s12967-025-07397-z (Full text)

Altered effort and deconditioning are not valid explanations of myalgic encephalomyelitis/chronic fatigue syndrome

Letter:

Response to B. Walitt et al. Nature Communications https://doi.org/10.1038/s41467-024-45107-3 (2024)

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex, systemic disease with significant pathophysiological uncertainties and variable presentations1. Here, we challenge Walitt et al.’s2 conclusion that post-infectious (PI) ME/CFS is a disorder defined by altered effort preference, leading to activity avoidance and subsequent deconditioning. We believe this interpretation risks reinforcing skepticism about the serious biological nature of ME/CFS and its hallmark of post-exertional malaise (PEM), as well as its potential misclassification as a mental health condition.

Walitt et al.2 utilized a single CPET to evaluate systems-level physiological responses to exercise. However, this methodology does not allow for measuring responses after an initial exertion, which is critically important for fully understanding PEM3. Over the past two decades, 2-day CPET has been used to characterize the systems-level metabolism of ME/CFS3. This paradigm uses an initial maximal CPET to establish the individual’s baseline performance and as a participant-referenced method to induce PEM4. A second maximal CPET is then conducted 24 h later to measure physiological and perceptual responses to exercise during the post-exertional state4. Standard objective criteria to evaluate effort are used to ensure maximal testing, including the respiratory exchange ratio at peak exertion4. This removes uncertainty related to effort. Meta-analyses involving participants with ME/CFS who have completed 2-day CPET indicate characteristic declines in the volume of oxygen consumed, work rate, and heart rate (HR) at submaximal exertion on the second CPET. These findings are reliably observed in people with ME/CFS but not deconditioned individuals5,6,7. Accordingly, the Institute of Medicine (IOM) cautioned that “a single CPET may be insufficient to document the abnormal response of ME/CFS patients to exercise.”1 (p. 106)

Using a single CPET introduces a threat to validity in Walitt et al.’s study2, as it did not allow for the measurement of submaximal performance decrement in the post-exertional state1,3,4,5,6. This is important because deconditioning and PEM are not mutually exclusive. Special care must be taken when applying and interpreting CPET results1. Failure to use 2-day CPET prevented the authors from adequately testing their conclusion that PEM is related to participants’ effort preference, as they did not evaluate physiological performance under conditions involving objective, standardized criteria for maximal exertion. Unfortunately, the use of a single CPET in this study contributed to the authors’ misinterpretation that PEM is synonymous with reduced effort and deconditioning.

Read the rest of this letter here: https://www.nature.com/articles/s41467-025-64538-0

Source: Davenport, T.E., Scheibenbogen, C., Zinn, M.A. et al. Altered effort and deconditioning are not valid explanations of myalgic encephalomyelitis/chronic fatigue syndrome. Nat Commun 16, 9176 (2025). https://doi.org/10.1038/s41467-025-64538-0 https://www.nature.com/articles/s41467-025-64538-0 (Full text)

Patients with severe ME/CFS deserve better than unproven theories

Rapid Response:

Patients with severe ME/CFS deserve better than unproven theories

Dear Editor

Miller et al argue that chronic fatigue conditions are “a dysfunctional biological response orchestrated in the brain, influenced by expectations and conditioned responses,” and as a result, even people with severe ME/CFS can recover by “reframing beliefs about illness, along with specialist rehabilitation.”

Interventions based on this model have been tested in randomised trials in people since the 1990s in people with mild to moderate symptoms. Many of the participants would not have had ME/CFS as currently diagnosed, which carries a higher risk of harm from exertion. [1-3] Even in that easier context, short-term effects have been negligible or modest, without longterm benefits. Harms were not thoroughly studied. [1-3] This does not amount to strong evidence of substantial symptomatic improvement, let alone disease modification or full recovery.

Miller et al offer no direct strong evidence to support their claim that with their approach, “even those with severe ME/CFS can recover.” They cite the experience of a unit in Leeds, based on charts of discharged patients from a quality assurance report, where no patients were rated as “not at all ill” on discharge. [4] This kind of data is not defined as research, intended to be generalisable to other patients. [5] It was a very small group, too: Only six of the patients in that report had the diagnosis ME/CFS.

The weight of the authors’ argument, then, relies on their pathophysiologic rationale, which does not account for the full range of physical impacts of the illness. They point to other literature positing similar hypotheses, but these theories remain unproven. The pathophysiology of ME/CFS remains uncertain, [1-3] and it is not even clear that there is just one type of ME/CFS with the same underlying mechanisms. [6] Heterogeneous results in studies that have attempted to establish a core part of the model – that activity level and biological impairment are related – may be related to varying diagnostic criteria. [7]

Medicine has a long history of ascribing beliefs and/or responses to stress as the cause of diseases that were not yet fully understood. It wasn’t all that long ago that asthma, rheumatoid arthritis, and peptic ulcers fell into this category. [8] It’s been proven wrong so often now, we should be highly skeptical of these theories.

Perhaps part of why psychologically-based rationales for disease can be widely accepted is because the harm this can do is underappreciated. Miller et al argued that their narrative inspires hope, and people with severe ME/CFS deserve that. But when the unproven theory can’t deliver on the claims, what then? In a study Miller et al cited, researchers found that being told the disease was psychosomatic was the most common reason for suicidal thoughts for people with ME/CFS. [9] It’s not the first study to suggest that being told they are effectively to blame for not recovering is a contributing factor to the increased risk of suicidality in people with ME/CFS. [10]

A critical part of hope for people suffering illness is being able to trust that the medical community will work objectively to find better treatments and ways to support them, rather than promote unproven theories. People with ME/CFS deserve better than being told that their minds can overcome what’s the matter with their bodies – if only they try hard enough, for long enough.

References

1. National Institute for Health and Care Excellence. Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management. 29 Oct 2021. https://www.nice.org.uk/guidance/ng206

2. Chou R, McDonagh M, Griffin JC, Grusing S. Management of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): An Updated Systematic Evidence Review prepared for Centers for Disease Control and Prevention. 2022. https://stacks.cdc.gov/view/cdc/156092

3. Institute for Quality and Efficiency in Health Care (IQWiG). Current scientific knowledge on myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). 2023. https://www.iqwig.de/en/projects/n21-01.html

4. Leeds and York Partnership NHS Foundation Trust. National Inpatient Centre for Psychological Medicine: annual review 2020-21. May 2021. https://www.leedsandyorkpft.nhs.uk/our-services/wp-content/uploads/sites…

5. Health Research Authority. Defining research. October 2022. https://www.hra-decisiontools.org.uk/research/docs/DefiningResearchTable…

6. Bastos VC, Greene KA, Tabachnikova A, et al. Cerebrospinal fluid immune phenotyping reveals distinct immunotypes of myalgic encephalomyelitis/chronic fatigue syndrome. J Immunol 2025;vkaf087. doi:10.1093/jimmun/vkaf087 pmid:40373264

7. Sunnquist M, Jason LA. A reexamination of the cognitive behavioral model of chronic fatigue syndrome. J Clin Psychol 2018;74:7. doi:10.1002/jclp.22593 pmid:29457646

8. Hange D, Bengtsson C, Sundh V, Bjorkelund. The natural history of psychosomatic symptoms and their association with psychological symptoms: Observations from the Population Study of Women in Gothenburg. Eur J Gen Pract 2007;13:2. doi:10.1080/13814780701377497 pmid:17534741

9. König RS, Paris DH, Sollberger M, Tschopp R. Identifying the mental health burden in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) patients in Switzerland: A pilot study. Heliyon 2024;10:e27031. doi:10.1016/j.heliyon.2024.e27031 pmid:3843435

10. Chu L, Elliott M, Stein E, Jason LA. Identifying and managing suicidality in Myalgic Encephalitis/Chronic Fatigue Syndrome. Healthcare (Basel) 2021;9:6. doi:10.3390/healthcare9060629 pmid:34070367

Source: Hilda Bastian. BMJ 2025;389:r977 https://www.bmj.com/content/389/bmj.r977/rr-30

Rate of 4.5% Post-COVID ME/CFS Onset Cited in Recent RECOVER Study is Based on Biased Cohort

Letter:

The recent paper by Vernon, et al.1 predicts that 4.5% of adult COVID sufferers in the United States experience subsequent onset of Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS). While the degree of ME/CFS onset is indeed significant, the figure of 4.5% cannot be justified from the provided data.

Vernon, et al. compute a male onset rate of 3.41% (107/3134, see Table 1 of paper) and a female onset rate of 4.91% (422/8600). They then take a weighted average based on the gender breakdown of their cohort, which is 27.7% male and 72.3% female, to arrive at 4.5% overall.

The problem here is that their cohort, which is nearly three-quarters female, is not representative of the adult gender prevalence of COVID in the United States. One can estimate the gender breakdown using the CDC Household Pulse Survey,2 which shows 61.6% of US adults having gotten COVID, 58.6% of males and 64.4% of females. These numbers are consistent with an assumed gender breakdown of the adult population of 48.3% male and 51.7% female, from which can be deduced an adult COVID breakdown of 46% male and 54% female, leading to an ME/CFS onset rate of 4.22%. While significant, this is less than the 4.5% published conclusion.

Source: Mirin AA. Rate of 4.5% Post-COVID ME/CFS Onset Cited in Recent RECOVER Study is Based on Biased Cohort. J Gen Intern Med. 2025 Jul 22. doi: 10.1007/s11606-025-09711-3. Epub ahead of print. PMID: 40696227.  https://link.springer.com/article/10.1007/s11606-025-09711-3 (Full text)

Reframing beliefs about their illness does not lead to recovery of tube-fed patients with very severe ME/CFS. Analysis of the BMJ article by Miller et al

Abstract:

The narrative which is presented by Miller et al. as new, has dominated the field of ME/CFS for the last 35 years. It has been tested by numerous studies and has been found to be ineffective and harmful, as concluded by for example NICE in 2021. Additionally, it does not lead to objective improvement and it has a negative instead of a positive effect on work and disability status.

What has happened over the last 35 years is that severely ill patients have been ridiculed, gaslit and ignored by the medical profession. These patients have lost hope in the part of the medical profession which has been instrumental in doing and promoting that. They have not lost hope to recover and they are all hoping to get effective pharmacological treatments sooner rather than later as changing their mindset does not lead to recovery. And if it does, then the diagnosis of ME/CFS was simply wrong.

Source: Vink, Mark and Vink-Niese, Friso, Reframing beliefs about their illness does not lead to recovery of tube-fed patients with very severe ME/CFS. Analysis of the BMJ article by Miller et al. (June 06, 2025). No., Available at SSRN: https://ssrn.com/abstract=5284667 https://papers.ssrn.com/sol3/papers.cfm?abstract_id=5284667 (Full text available as PDF file)

Response to treatment in the Multiple Symptoms Study 3 trial

Letter:
Chistopher Burton and colleagues conducted an unblinded trial of a consultative intervention for 354 people with persistent physical symptoms but no identifiable “organic” cause. Patient Health Questionnaire-15 (PHQ-15) score, which is a brief, subjective, self-administered screen of severity of somatic complaints, was the primary outcome. This kind of trial design can be expected to produce modest positive outcomes, via expectation bias alone. No real-life, objective assessment of functioning was conducted.
The intervention involved up to four sessions with a general practitioner, offering patients “rational explanations” for their symptoms in the absence of known, falsifiable causes and helping patients to develop strategies for managing symptoms. Although the “rational explanations” are not described, they presumably did not include “organic” diseases or conditions.
Scores on the PHQ-15 range from 0 to 30. Recruited patients had scores from 10 to 20, indicating moderate severity. At the end of the study, the adjusted between-group difference of –1·82 did not reach the minimal clinically important difference of 2·3. The change is well within what would be expected from bias alone. The results therefore confirmed that the intervention was of limited, if any, practical benefit. However, the paper presents the findings as though they had shown the opposite.
Instead of the “rational explanations” promoted by the investigators, more straightforward and honest explanations—for example, we do not know what is causing symptoms—could easily have produced similar results. Patients desire resolution of symptoms and recovery of functions. The trial did not achieve this result. Post-intervention, participants continue to have an impaired quality of life and poor experiences of health care.
DT holds an academic position at the Center for Global Public Health at UC Berkeley, which is largely supported by crowdfunded donations directly to the university, many of them from patients with myalgic encephalomyelitis or chronic fatigue syndrome and related conditions that fall under the heading of persistent physical symptoms. JSC declares no competing interests.
Source: Joan S Crawford and David Tuller. Response to treatment in the Multiple Symptoms Study 3 trial.  The Lancet, Volume 405, Issue 10485, 1145 – 1146  https://link.springer.com/article/10.1007/s00421-025-05759-5 (Full text)

Letter: Time to correct the record on the global burden of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)

Dear Editor,

We have read Lim et al.’s study [1] with great interest. Studies of this illness are scarce, so their article is important in establishing the global prevalence systematically. In fact, it has been cited over 200 times and has had a significant influence on global reporting of the burden of ME/CFS. Unfortunately, the core figure that is most frequently drawn from the article is a significant underestimate of the prevalence of ME/CFS, and has led to the spread of misinformation about the burden of this disease.

A global ME/CFS population of 17 to 24 million people is reported in articles such as those published in BMC Medicine [2] and Science [3], all referencing Lim et al. The same range of numbers is also easy to find in patient advocacy websites and news reports, such as those of the American Myalgic Encephalomyelitis and Chronic Fatigue Syndrome Society [4] and CNN [5], all updated after Lim et al.’s article was published. However, this figure is drawn from the Background section of Lim et al.’s article, where they state, “In worldwide statistics, approximately 1% of the population, 17 to 24 million people, suffer from this condition [14], which is likely to be as common as rheumatoid arthritis” [1]. The cited reference (reference [14]) is an article about the global burden of multiple sclerosis, and is not relevant to the global ME/CFS population.

The actual headline result of the study by Lim et al. was an estimated prevalence of 0.89% using the CDC-1994 definition, as indicated in the Discussion and Conclusions sections of their article [1]. If we correctly apply this to the global population of 8 billion, the true prevalence of ME/CFS would be 71.2 million (71,200,000). However, new research using more up-to-date datasets and methods is essential to gain a full understanding of the burden of this disease.

Due to this unfortunate misreading and misattribution by others of an erroneous reference in the Background section of Lim et al.’s article, there is widespread underestimation of the true burden of ME/CFS. Such underestimation may exacerbate the isolation, stigmatization, and suffering of people living with this poorly-understood and under-recognized illness. More effort is needed to correct this underestimation globally, develop treatment methods and welfare support, and relieve the burden of ME/CFS. Correct reporting of the true prevalence of this disease is an important first step to addressing the ongoing neglect that its sufferers experience, and this can begin with the correct reporting of Lim et al.’s research.

Source: Vardaman M, Gilmour S. Letter: Time to correct the record on the global burden of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). J Transl Med. 2025 Mar 14;23(1):331. doi: 10.1186/s12967-025-06281-0. PMID: 40087760. https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-025-06281-0 (Full text)

Recognizing the role of fibromyalgia in post-exertional malaise

Letter:

The recent opinion by Charlton et al. published in Trends in Endocrinology & Metabolism [] provides a thought-provoking discussion of the overlap between long coronavirus disease (long-COVID) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), emphasizing the centrality of post-exertional malaise (PEM) as a shared mechanism.

Here, we suggest that fibromyalgia should be included in the discussion, given the established role of PEM in this condition []. In addition, fibromyalgia not only shares symptomatic and mechanistic overlaps with ME/CFS, but also offers a complementary perspective on the pathophysiology of PEM. Considering that PEM is a key symptom in both fibromyalgia and long COVID, exploring skeletal muscle function in fibromyalgia could provide complementary insights into the muscle-specific alterations that contribute to this debilitating phenomenon.

Source: Giollo A, Salvato M, Doria A. Recognizing the role of fibromyalgia in post-exertional malaise. Trends Endocrinol Metab. 2025 Mar 11:S1043-2760(25)00045-1. doi: 10.1016/j.tem.2025.02.005. Epub ahead of print. PMID: 40074568. https://www.cell.com/trends/endocrinology-metabolism/abstract/S1043-2760(25)00045-1

On the Prevalence of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome after a SARS-CoV-2 infection

Introduction:

There is an increasing body of evidence connecting the post-acute SARS-CoV-2 condition (PASC, commonly known as long COVID) to Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), a debilitating disease of unknown cause characterized by persistent and unexplained fatigue, post-exertional malaise (PEM), among other symptoms. This connection implies that, in the clinic, some PASC cases comply with the official case definitions of ME/CFS. As such, there is a necessity to quantify the burden of ME/CFS among the PASC population in order to delineate effective healthcare interventions for the benefit of these patients who are often neglected or, in some extreme cases, stigmatized by medical staff and society.
To answer this urgent research question, Dehlia and Guthridge performed a systematic review and meta-analysis of recent data on PASC adults and reported an ME/CFS prevalence estimate of 51% (95% CI, 42%-60%); this systematic review and meta-analysis will be referred to as PASC-ME/CFS study. In the present Letter to Editor, we aimed to discuss the reliability of this estimate using the research protocol from the European Network on ME/CFS (EUROMENE) for systematic reviews and meta-analysis on the epidemiology burden of ME/CFS in Europe.

Source: Sepúlveda N, Westermeier F. On the Prevalence of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome after a SARS-CoV-2 infection. J Infect. 2024 Nov 16:106353. doi: 10.1016/j.jinf.2024.106353. Epub ahead of print. PMID: 39557089. Sepúlveda N, Westermeier F. On the Prevalence of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome after a SARS-CoV-2 infection. J Infect. 2024 Nov 16:106353. doi: 10.1016/j.jinf.2024.106353. Epub ahead of print. PMID: 39557089. https://www.journalofinfection.com/article/S0163-4453(24)00288-3/fulltext (Full text)