Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Complex MONDO:0005404 Pathograph 34 Show in embeddings browser Neurological Disorder Immune Disorder

ME/CFS is a chronic, fluctuating multisystem illness defined by substantial loss of previous function, post-exertional symptom exacerbation, unrefreshing sleep, and cognitive or orthostatic symptoms. Infection can precede onset, but no single cause, diagnostic biomarker or disease-modifying treatment is established. Neurovascular, immune, metabolic and central abnormalities vary by cohort; the integrated mechanism of delayed PEM remains unresolved.

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Subtypes

Mild ME/CFS

Able to manage personal care and some domestic activity, often with reduced hours and loss of leisure or social activity. These NICE severity grades can fluctuate; they are not etiologic categories.

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"People with mild ME/CFS care for themselves"

NICE severity definitions guide support needs.

Moderate ME/CFS

Reduced mobility and restricted daily activities, usually unable to continue work or education and requiring daytime rest. These NICE severity grades can fluctuate; they are not etiologic categories.

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"People with moderate ME/CFS have reduced mobility"

NICE severity definitions guide support needs.

Severe ME/CFS

Minimal self-care, major cognitive and sensory burden, often housebound or predominantly bedbound. These NICE severity grades can fluctuate; they are not etiologic categories.

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"They may also spend most of their time in bed"

NICE severity definitions guide support needs.

Very Severe ME/CFS

Bedbound and dependent on care, with marked sensory intolerance and sometimes inability to swallow. These NICE severity grades can fluctuate; they are not etiologic categories.

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"are in bed all day and dependent on care."

NICE severity definitions guide support needs.

◈

Mechanistic Hypotheses

TRPM3-Dependent NK-Cell Calcium and Effector Function

trpm3_nk_calcium_effector_hypothesis EMERGING

Evidence balance 1 support

Altered TRPM3-dependent calcium signaling may impair NK-cell cytotoxic function. Patient-cell current and calcium assays support upstream abnormalities, but downstream mediation, patient-wide generality and symptom benefit from channel rescue remain unresolved.

Pathograph links

TRPM3-Associated NK-Cell Calcium Dysregulation -> Natural Killer Cell Dysfunction INDIRECT UNKNOWN INTERMEDIATES Proposed calcium-dependent impairment of NK-cell effector function. The directed hypothesis does not assert reverse causation, uniform NK dysfunction across cohorts or clinical efficacy of naltrexone.

Show evidence (1 reference)

PMID:42177403 SUPPORT Other

"In NK cells, impaired TRPM3 channel function may lead to dysregulated Ca2+ signalling, subsequently disrupting ATP production, and Ca2+-dependent signalling events, thereby impacting cytotoxic activity and broader immune dysfunction."

The study figure describes a conceptual downstream model. Patient-cell calcium responses were measured, but mediation of cytotoxicity or its rescue was not established by this experiment.

Exertion-Perfusion-Muscle Immunometabolic PEM Model

exertion_perfusion_muscle_immunometabolic_pem_model EMERGING

Evidence balance 9 support

Exertion may expose neurovascular or muscle metabolic limitations in a subset of patients, followed by delayed immune and central amplification of symptoms. Low-flow preload failure, high-flow impaired extraction, tissue sodium changes and immune-state abnormalities are distinct observations. The ordering and necessity of the proposed links remain unresolved.

Retain EMERGING after source-level assessment of OpenScientist. Corrected its false absence of sodium MRI and acute hemodynamic intervention evidence, 50% small-fiber-neuropathy figure (31% in the cited cohort), review-as-primary EM attribution and cohort conflations. The 2024 EM study lacks healthy EM controls; the exercise-biopsy study is in long COVID and does not demonstrate intravascular microclots. A 2022 sodium MRI pilot measures mixed tissue sodium, not isolated intracellular sodium or calcium overload. Acute pyridostigmine improves exercise hemodynamics but does not establish durable PEM benefit. Positive and negative day-two CPET studies coexist. None of these findings proves an obligatory muscle-to-immune-to-CNS sequence or validated biological subtype boundaries.

Pathograph links

Small-Fiber Neuropathy -> Impaired Venous Return INDIRECT UNKNOWN INTERMEDIATES Proposed loss of effective venoconstriction could reduce cardiac return. The pathway was not directly demonstrated, and biopsy denervation severity did not correlate with exertional measures.

Small-Fiber Neuropathy -> Impaired Peripheral Oxygen Extraction INDIRECT UNKNOWN INTERMEDIATES Proposed microvascular shunting; the mechanism remains inferred from physiology, without direct capillary shunt imaging.

Impaired Peripheral Oxygen Extraction -> Exercise Intolerance INDIRECT UNKNOWN INTERMEDIATES Reduced extraction limits usable oxygen during exertion in this selected subgroup.

Impaired Peripheral Oxygen Extraction -> Skeletal Muscle Bioenergetic Disturbance INDIRECT UNKNOWN INTERMEDIATES The proposed link from oxygen-use limitation to myocyte metabolic disturbance has not been tested with simultaneous patient-level perfusion and muscle assays.

Endothelial Vasodilator Dysfunction -> Skeletal Muscle Bioenergetic Disturbance INDIRECT UNKNOWN INTERMEDIATES Possible impaired delivery to exercising muscle; the FMD/PORH study did not establish this causal bridge.

Reduced Erythrocyte Deformability -> Myalgia INDIRECT UNKNOWN INTERMEDIATES Hypothetical symptom contribution through impaired microvascular perfusion and tissue oxygenation, as proposed by the assay authors; in vivo perfusion and symptom mediation remain untested.

Reduced Erythrocyte Deformability -> Fatigue INDIRECT UNKNOWN INTERMEDIATES Hypothetical symptom contribution through impaired microvascular perfusion and tissue oxygenation, as proposed by the assay authors; in vivo perfusion and symptom mediation remain untested.

Skeletal Muscle Bioenergetic Disturbance -> Proposed Delayed Immunometabolic Amplification INDIRECT UNKNOWN INTERMEDIATES Proposed muscle metabolite or injury signals could amplify delayed symptoms. No source-to-target tracing or integrated perturbation demonstrates this step.

Elevated Skeletal Muscle Tissue Sodium -> Proposed Muscle Sodium-Calcium Loading INDIRECT UNKNOWN INTERMEDIATES Hypothetical interpretation: if elevated tissue sodium includes sufficiently elevated myocyte sodium, exchanger reversal could promote calcium loading. MRI compartment mixing and the absence of direct calcium measurements leave this transition unverified.

Proposed Muscle Sodium-Calcium Loading -> Skeletal Muscle Bioenergetic Disturbance INDIRECT UNKNOWN INTERMEDIATES Predicted calcium toxicity to myocytes and mitochondria; retain as a hypothetical link requiring compartment-specific measurement and perturbation.

Proposed Delayed Immunometabolic Amplification -> Post-Exertional Malaise INDIRECT UNKNOWN INTERMEDIATES Hypothesized delayed amplification of symptoms; clinical PEM is established while this molecular sequence remains unproven.

Proposed Peripheral Vesicle-Microglial Signaling -> Possible Neuroimmune Activation INDIRECT UNKNOWN INTERMEDIATES Hypothetical extension of vesicle-preparation bioactivity to neuroimmune activation in patients. This requires biologically effective CNS exposure and in vivo confirmation; neither is demonstrated by the cultured-cell assay.

Deep research

OpenScientist citations 29 citations 2026-06-03T10:15:53.121961

Show evidence (9 references)

PMID:33577778 SUPPORT Human Clinical

"These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction."

Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.

PMID:36494667 SUPPORT Human Clinical

"Baseline tissue sodium content was higher in all 5 lower leg muscle compartments in ME/CFS compared to controls."

Six female cases and six matched controls underwent sodium MRI before and after three minutes of plantar flexion. The acquisition could not isolate intracellular from extracellular sodium.

PMID:35526605 SUPPORT Human Clinical

"The peak Vo2 increased after pyridostigmine but decreased after placebo (13.3 ± 13.4 mL/min vs -40.2 ± 21.3 mL/min; P < .05)."

Randomized 45-person acute trial: 60 mg pyridostigmine between two iCPETs separated by 50 minutes improved the relative exercise response. This does not test delayed PEM or durable treatment benefit.

+ 6 more references

Discussions and Knowledge Gaps

Which causal edge best connects exertion to delayed multi-system symptom worsening in ME/CFS: impaired microvascular oxygen delivery/extraction, skeletal muscle ionic and mitochondrial disturbance, immune-metabolic signaling, autonomic dysfunction, central nervous system amplification, or a subtype-specific combination?

KNOWLEDGE GAP OPEN gap_mecfs_pem_causal_ordering

Attached to

pathophysiology#Impaired Peripheral Oxygen Extraction pathophysiology#Skeletal Muscle Bioenergetic Disturbance pathophysiology#Proposed Delayed Immunometabolic Amplification phenotypes#Post-Exertional Malaise

No study in the reviewed literature measures and perturbs the complete peripheral-perfusion, myocyte-ion, metabolic, immune and CNS sequence in the same ME/CFS participants. Existing sodium MRI, acute pyridostigmine, single-cell exercise and long-COVID muscle-biopsy studies narrow the gaps; they do not validate the entire chain. Muscle sodium compartment specificity, causal ordering, subgroup boundaries and physiological/symptom discordance remain open. A 2022 patient serum-vesicle/microglial assay demonstrates peripheral-preparation bioactivity but not muscle source, mtDNA-specific causality, BBB transport or in vivo brain effects.

Proposed experiments

Serial exertion-challenge perfusion and muscle multi-omics cohort

longitudinal exertion-challenge cohort

exp_mecfs_pem_serial_exertion_perfusion_multiomics

Use a prospectively registered, severity-adapted cohort with activity-matched controls and carefully tolerated provocation. Measure symptoms and selected perfusion, muscle metabolism, sodium-compartment, immune and autonomic endpoints across baseline, immediate, 24–72-hour and recovery windows. An invasive or maximal exercise battery should not be imposed on people unable to tolerate it. Specify missing-data handling, medication/activity covariates and independent validation before subgroup discovery.

Model systems

Human ME/CFS exertion-challenge cohort

Patient cohort designed to temporally order peripheral perfusion, skeletal muscle, metabolic, immune, autonomic, and symptom readouts during PEM induction and recovery.

OTHER

human NCBITaxon:9606

Decision criterion

Temporal precedence and adjusted mediation would increase plausibility but would not establish causality because unmeasured confounding and feedback remain possible. A targeted randomized perturbation must demonstrate target engagement and downstream physiological and symptom changes, with rescue and safety outcomes, to test direction. Compartment-specific sodium results are needed before inferring intracellular calcium loading.

Would support

pathophysiology#Impaired Peripheral Oxygen Extraction pathophysiology#Skeletal Muscle Bioenergetic Disturbance pathophysiology#Proposed Delayed Immunometabolic Amplification

Would refute

mechanistic_hypotheses#exertion_perfusion_muscle_immunometabolic_pem_model

Show evidence (2 references)

PMID:36153118 SUPPORT Human Clinical

"Here, we show that mitochondrial DNA (mtDNA) associated with serum exosomes, is increased in ME/CFS patients only after exercise."

The publication reports paired patient exercise-associated change; an equivalently exercised healthy-control series is not demonstrated.

PMID:36153118 SUPPORT In Vitro

"Moreover, exosomes isolated from patients with ME/CFS stimulate significant release of IL-1β from cultured human microglia."

Patient serum vesicle preparations have in vitro bioactivity. This does not establish mtDNA necessity, muscle origin, BBB passage or human brain inflammation.

Which ME/CFS susceptibility variants act through which tissues and effector genes?

KNOWLEDGE GAP OPEN gap_mecfs_genetic_architecture

The 2025 DecodeME preprint reports eight associated loci in up to 15,579 cases and 259,909 ancestry-matched controls. It is not peer reviewed, and nearby genes are not proven effector genes. HLA and GWAS findings support polygenic susceptibility without establishing Mendelian inheritance, a clinical test or this specific perfusion-to-PEM pathway.

Show evidence (1 reference)

DOI:10.1101/2025.08.06.25333109 Preprint · not peer-reviewed SUPPORT Human Clinical

"We recruited 21,620 ME/CFS cases and performed genome-wide association studies (GWAS) for up to 15,579 cases and 259,909 population controls with European genetic ancestry."

DecodeME is a preprint; locus associations do not identify causal effector genes.

Do receptor autoantibodies, microbial metabolites or central regulatory abnormalities initiate or maintain the observed neurovascular and immune states?

KNOWLEDGE GAP OPEN gap_mecfs_upstream_alternatives

These hypotheses may complement rather than exclude the perfusion model. Receptor-antibody concentration associations do not establish receptor agonism or causality; microbial metabolite associations do not prove barrier leakage. An older central activation study provides an alternative physiological direction. Negative rituximab evidence and extracellular rather than intravascular muscle amyloid deposits constrain overly simple autoimmune and microclot models.

Show evidence (5 references)

PMID:33889154 SUPPORT Human Clinical

"could not confirm diagnostic suitability"

sCD26 and autoantibody correlations were subgroup dependent and did not establish a diagnostic assay or receptor dysfunction.

PMID:8423875 SUPPORT Human Clinical

"The results indicate that patients with CFS have (1) normal fatigability and metabolism at both the intracellular and systemic levels, (2) normal muscle membrane function and excitation-contraction coupling, and (3) an inability to fully activate skeletal muscle during intense, sustained exercise."

This older isometric-muscle study supports altered central activation in its cohort, not a psychiatric explanation or a universal exclusion of peripheral pathology.

PMID:38177128 SUPPORT Human Clinical

"We conclude that amyloid-containing deposits are not present within capillaries."

The 25-person long-COVID PEM cohort and 21 recovered controls had paired biopsies. Deposits were extravascular; this contradicts equating the observation with occlusive muscle microclots.

+ 2 more references

⚙

Pathophysiology

Small-Fiber Neuropathy

Reduced epidermal small-fiber density occurs in a subset of selected patients. Autonomic small-fiber dysfunction could affect venous tone or distribution of muscle blood flow, but skin-fiber density does not directly establish either mechanism.

Exertion-Perfusion-Muscle Immunometabolic PEM Model

Downstream

Impaired Venous Return Proposed loss of effective venoconstriction could reduce cardiac return. The pathway was not directly demonstrated, and biopsy denervation severity did not correlate with exertional measures.

Impaired Peripheral Oxygen Extraction Proposed microvascular shunting; the mechanism remains inferred from physiology, without direct capillary shunt imaging.

Show evidence (1 reference)

PMID:33577778 SUPPORT Human Clinical

"Among the 160 ME/CFS patient biopsies, 31% were consistent with SFN (epidermal innervation ≤5.0% of predicted; P < .0001). Denervation severity did not correlate with exertional measures."

The ME/CFS biopsy proportion was 31%, not the report's approximately 50%; the latter is background POTS/fibromyalgia literature. A shunting mechanism is proposed rather than causally demonstrated.

Impaired Venous Return

Low cardiac filling pressure is present in the selected iCPET cohort. Low right-atrial pressure was an inclusion criterion, so this finding cannot establish its frequency throughout ME/CFS.

Downstream

Reduced Exercise Cardiac Output Impaired filling limits cardiac output during upright exertion in the low-flow phenotype.

Show evidence (1 reference)

PMID:33577778 SUPPORT Human Clinical

Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.

Reduced Exercise Cardiac Output

The low-flow subgroup has reduced exercise cardiac output, limiting oxygen delivery. It is distinct from the high-flow oxygen-extraction phenotype.

Downstream

Exercise Intolerance Reduced exercise oxygen delivery contributes to limited aerobic capacity in this physiological subgroup.

Show evidence (2 references)

PMID:33577778 SUPPORT Human Clinical

Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.

PMID:35526605 SUPPORT Human Clinical

"The peak Vo2 increased after pyridostigmine but decreased after placebo (13.3 ± 13.4 mL/min vs -40.2 ± 21.3 mL/min; P < .05)."

Randomized 45-person acute trial: 60 mg pyridostigmine between two iCPETs separated by 50 minutes improved the relative exercise response. This does not test delayed PEM or durable treatment benefit.

Impaired Peripheral Oxygen Extraction

High-flow patients have reduced systemic oxygen extraction despite preserved flow. Maldistributed flow and cellular oxygen use are candidate explanations; impaired extraction is not equivalent to reduced total limb perfusion.

Exertion-Perfusion-Muscle Immunometabolic PEM Model

Downstream

Exercise Intolerance Reduced extraction limits usable oxygen during exertion in this selected subgroup.

Skeletal Muscle Bioenergetic Disturbance The proposed link from oxygen-use limitation to myocyte metabolic disturbance has not been tested with simultaneous patient-level perfusion and muscle assays.

Show evidence (1 reference)

PMID:33577778 SUPPORT Human Clinical

Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.

Endothelial Vasodilator Dysfunction

Reduced brachial flow-mediated dilation and skin reactive hyperemia indicate vascular dysfunction in some cohorts. These measurements do not directly demonstrate capillary obstruction or muscle ischemia.

Exertion-Perfusion-Muscle Immunometabolic PEM Model

endothelial cell CL:0000115

vasodilation GO:0042311

Downstream

Skeletal Muscle Bioenergetic Disturbance Possible impaired delivery to exercising muscle; the FMD/PORH study did not establish this causal bridge.

Show evidence (1 reference)

PMID:36730360 SUPPORT Human Clinical

"ME/CFS patients had markedly reduced FMD compared to healthy controls at baseline (5.1% vs. 8.2%, p< 0.0001, adjusted for arterial diameter and sex), and significantly lower microvascular regulation measured by PORH than healthy controls (1354 PU vs. 2208 PU, p = 0.002)."

Sandvik and colleagues studied 39 RituxME participants; macrovascular FMD and skin PORH are distinct from direct exercising-muscle perfusion. The two measures did not correlate.

Reduced Erythrocyte Deformability

Patient erythrocytes had lower deformability in a small microfluidic study. This has not established in vivo capillary plugging, thrombosis, or a clinical diagnostic assay.

Exertion-Perfusion-Muscle Immunometabolic PEM Model

erythrocyte CL:0000232

Experimental models

Erythrocyte Microfluidic Deformability Assay OTHER Microfluidic transit assays measure altered deformability of patient erythrocytes.

Downstream

Myalgia Hypothetical symptom contribution through impaired microvascular perfusion and tissue oxygenation, as proposed by the assay authors; in vivo perfusion and symptom mediation remain untested.

Fatigue Hypothetical symptom contribution through impaired microvascular perfusion and tissue oxygenation, as proposed by the assay authors; in vivo perfusion and symptom mediation remain untested.

Show evidence (1 reference)

PMID:30594919 SUPPORT In Vitro

"We observed from various measures of deformability that the RBCs isolated from ME/CFS patients were significantly stiffer than those from healthy controls."

Sixteen case-control pairs tested in a microfluidic device; the proposed in vivo perfusion consequence and diagnostic performance remain unvalidated.

Skeletal Muscle Bioenergetic Disturbance

Muscle studies suggest substrate-specific metabolic abnormalities and heterogeneous structural findings. In vitro glucose oxidation, cross-sectional EM and long-COVID paired biopsies address different questions. Neither universal fatty-acid oxidation failure nor a single primary mitochondrial lesion is established.

Exertion-Perfusion-Muscle Immunometabolic PEM Model

cell of skeletal muscle CL:0000188

oxidative phosphorylation GO:0006119

Experimental models

Patient-Derived Skeletal Myotubes PRIMARY CELL CULTURE Patient-derived myotubes show impaired glucose oxidation with preserved galactose and fatty-acid oxidation in substrate-specific culture assays.

Downstream

Proposed Delayed Immunometabolic Amplification Proposed muscle metabolite or injury signals could amplify delayed symptoms. No source-to-target tracing or integrated perturbation demonstrates this step.

Show evidence (5 references)

PMID:33106563 SUPPORT In Vitro

"galactose and fatty acids normally, indicating that the bioenergetic dysfunction lies upstream of the TCA cycle."

Cultured myotubes from nine CFS and eleven control donors had substrate-dependent glucose-use abnormalities; persistence in culture is not proof of a genetic defect.

PMID:38338957 SUPPORT Human Clinical

"Due to the lack of an EM control group, the mean size and shape of CFS and PCS can only be compared between the respective syndromes."

The direct 2024 study compared mitochondrial ultrastructure in 14 CFS and 14 PCS samples without healthy EM controls. OXPHOS used historical healthy controls; between-syndrome morphology does not prove calcium-mediated injury.

PMID:9527150 SUPPORT Human Clinical

"No significant ultrastructural abnormalities were found."

An older 105-case biopsy study examined 41 samples by EM; findings qualify a universal structural mitochondrial lesion.

+ 2 more references

Elevated Skeletal Muscle Tissue Sodium

A 2022 pilot found higher MRI tissue sodium at rest and after brief exercise. Echo-time and compartment mixing prevent interpreting the signal as a direct measure of intracellular sodium or calcium overload.

Exertion-Perfusion-Muscle Immunometabolic PEM Model

cell of skeletal muscle CL:0000188

muscle tissue sodium homeostasis GO:0055078 ↕ DYSREGULATED

Downstream

Proposed Muscle Sodium-Calcium Loading Hypothetical interpretation: if elevated tissue sodium includes sufficiently elevated myocyte sodium, exchanger reversal could promote calcium loading. MRI compartment mixing and the absence of direct calcium measurements leave this transition unverified.

Show evidence (1 reference)

PMID:36494667 SUPPORT Human Clinical

"Baseline tissue sodium content was higher in all 5 lower leg muscle compartments in ME/CFS compared to controls."

Six female cases and six matched controls underwent sodium MRI before and after three minutes of plantar flexion. The acquisition could not isolate intracellular from extracellular sodium.

Proposed Muscle Sodium-Calcium Loading

The NHE1 sodium-loading, reduced Na/K-pump activity and reversed sodium/calcium-exchanger model predicts calcium-mediated mitochondrial injury. The sodium MRI pilot does not isolate intracellular sodium; direct human muscle calcium overload and exchanger reversal remain unverified.

Exertion-Perfusion-Muscle Immunometabolic PEM Model

Downstream

Skeletal Muscle Bioenergetic Disturbance Predicted calcium toxicity to myocytes and mitochondria; retain as a hypothetical link requiring compartment-specific measurement and perturbation.

Show evidence (2 references)

PMID:39727052 SUPPORT Other

"The sodium‐calcium exchanger (NCX) changes into reverse transport mode importing calcium instead of exporting it"

This is a proposed mechanism in a narrative review, not a direct human measurement.

PMID:36494667 SUPPORT Human Clinical

"Baseline tissue sodium content was higher in all 5 lower leg muscle compartments in ME/CFS compared to controls."

Six female cases and six matched controls underwent sodium MRI before and after three minutes of plantar flexion. The acquisition could not isolate intracellular from extracellular sodium.

Purine and Systemic Metabolite Alterations

Lower plasma hypoxanthine correlates with recent PEM severity. Broad plasma metabolomic differences vary by sex and cohort; concentrations do not prove flux, whole-body hypermetabolism, muscle source or dauer-like causation.

purine nucleotide metabolic process GO:0006163

Show evidence (2 references)

PMID:31277442 SUPPORT Human Clinical

"The principal biochemical change related to the 7-day severity of PEM was the fall in the purine metabolite, hypoxanthine."

Forty-seven cases reported recent PEM severity; a seven-day symptom window is not a serial provoked exercise experiment or a direct measurement of metabolic flux.

PMID:27573827 SUPPORT Human Clinical

"Eighty percent of the diagnostic metabolites were decreased, consistent with a hypometabolic syndrome."

The study had 45 cases and 39 controls, 84 total. Concentration profiles and internal classification do not establish organism-wide metabolic shutdown or a validated diagnostic test.

Classical Monocyte State Dysregulation

Single-cell profiles indicate altered differentiation and migration programs at baseline, including heterogeneous cell states within patients. Actual tissue invasion is not demonstrated by these data.

classical monocyte CL:0000860

Show evidence (1 reference)

PMID:38232699 SUPPORT Human Clinical

"At baseline, ME/CFS patients display classical monocyte dysregulation suggestive of inappropriate differentiation and migration to tissue."

Single-cell transcriptional association; actual tissue migration and its causal contribution to PEM were not directly measured.

Post-Exertional Platelet Transcriptional Dysregulation

Exercise-associated platelet activation signatures provide a specific immune-vascular observation. They do not establish widespread occlusive microclots or a generalized cytokine surge.

platelet CL:0000233

platelet activation GO:0030168

Show evidence (1 reference)

PMID:38232699 SUPPORT Human Clinical

"Comparing the transcriptome at baseline and postexercise challenge, we discover patterns indicative of improper platelet activation in patients, with minimal changes elsewhere in the immune system."

Exercise-associated platelet signatures do not establish a generalized cytokine cascade or occlusive microthrombosis.

Natural Killer Cell Dysfunction

Average NK cytotoxicity is reduced across many studies, but methods and cohorts differ and some large studies are negative. The relationship to infection persistence, individual symptoms and treatment response remains unresolved.

natural killer cell CL:0000623

Show evidence (2 references)

PMID:39483457 SUPPORT Other

"Cytotoxicity in ME/CFS was significantly reduced to about half of healthy control levels, with an overall Hedges' g of 0.96 (0.75-1.18). Heterogeneity was high but was explained by the range of E:T ratios, different methods, and potential outliers."

The meta-analysis supports reduced average cytotoxicity, with assay heterogeneity; it is not a universal individual diagnostic marker.

PMID:31057538 SUPPORT Human Clinical

"Contrary to previous reports, no significant differences were observed in NK cell numbers, subtype proportions or in vitro responsiveness between ME/CFS patients and healthy control participants."

The 251-case biobank study, including 54 severe cases, did not reproduce these NK abnormalities; its assays and sample handling differ from cytotoxicity studies.

TRPM3-Associated NK-Cell Calcium Dysregulation

Patient NK cells show altered TRPM3 currents and stimulus-dependent calcium responses. Re-addition of extracellular calcium produced higher mitochondrial influx but lower cytosolic influx; pregnenolone-sulfate/TRPM3-dependent responses were reduced in both compartments. Ex vivo naltrexone rescue does not establish clinical benefit or the same defect in muscle or autonomic neurons.

TRPM3-Dependent NK-Cell Calcium and Effector Function

natural killer cell CL:0000623

calcium ion transmembrane transport GO:0070588

Experimental models

Patient NK-Cell TRPM3 Assays PRIMARY CELL CULTURE Patch-clamp and compartment-specific calcium measurements identify condition-dependent NK-cell abnormalities; IL-2/naltrexone experiments test ex vivo channel rescue.

Downstream

Natural Killer Cell Dysfunction Proposed calcium-dependent impairment of NK-cell effector function. The directed hypothesis does not assert reverse causation, uniform NK dysfunction across cohorts or clinical efficacy of naltrexone.

Show evidence (2 references)

PMID:31736966 SUPPORT In Vitro

"TRPM3 channel activity was restored in IL-2 stimulated NK cells isolated from ME/CFS patients after incubation for 24 h with NTX."

Eight patient and eight control donors; ex vivo rescue does not demonstrate improvement of autonomic symptoms or PEM.

PMID:42177403 SUPPORT In Vitro

"Cytosolic Ca2+ influx amplitude and slope were significantly reduced (p < 0.001), with a significantly shorter T1/2 response (p = 0.001) in ME/CFS compared to HC. Ca2+ influx amplitude (p < 0.001) and slope (p < 0.041) into the mitochondria were significantly higher in ME/CFS compared to HC...."

Ten cases and ten controls: calcium re-addition produced higher mitochondrial influx despite lower cytosolic response, whereas pregnenolone-sulfate/TRPM3-dependent cytosolic and mitochondrial responses were both reduced. These are stimulus-specific NK-cell assays, not muscle calcium measurements.

Adaptive Immune Memory Dysregulation

Naive and switched-memory B-cell shifts in a selected post-infectious cohort suggest altered immune history. Persistent antigen identity and a causal role in PEM are unproven; negative rituximab results limit simple therapeutic extrapolation.

naive B cell CL:0000788 class switched memory B cell CL:0000972

Show evidence (1 reference)

DOI:10.1038/s41467-024-45107-3 SUPPORT Human Clinical

"Immune profiling suggested chronic antigenic stimulation with increase in naïve and decrease in switched memory B-cells."

Selected deep-phenotyping cohort of 17 post-infectious cases and 21 controls; antigen persistence and causality were inferred, not identified.

T-Cell Immunometabolic Dysfunction

Resting T-cell glycolysis and CD8 mitochondrial membrane potential are reduced in patient-cell assays, with activation-dependent differences. This does not demonstrate a uniform defect in all tissues.

CD8-positive, alpha-beta T cell CL:0000625 CD4-positive, alpha-beta T cell CL:0000624

glycolytic process GO:0006096

Experimental models

Patient T-Cell Metabolic Assays PRIMARY CELL CULTURE Resting CD4/CD8 and activated CD8 assays measure reduced glycolysis in patient cells; this does not establish global respiratory failure.

Show evidence (1 reference)

PMID:31830003 SUPPORT In Vitro

"Both CD4+ and CD8+ T cells from patients with ME/CFS had reduced glycolysis at rest, whereas CD8+ T cells also had reduced glycolysis following activation."

Primary patient-cell metabolism study with 53 cases and 45 controls; this does not establish universal mitochondrial respiratory failure.

CD8 T-Cell Exhaustion-Associated State

Transcription, chromatin accessibility and surface-marker data support an exhaustion-associated state in selected T-cell subsets. The causal antigen and clinical value of reversing this state remain unknown.

CD8-positive, alpha-beta T cell CL:0000625

exhausted T cell differentiation GO:0160083

Show evidence (1 reference)

DOI:10.1073/pnas.2415119121 SUPPORT Human Clinical

"We observed upregulation of key transcription factors associated with T cell exhaustion in CD8+ T cell effector memory subsets, as well as an altered chromatin landscape and metabolic reprogramming consistent with an exhausted immune cell state."

Multimodal profiling supports an exhaustion-associated state. The responsible antigen and benefit of checkpoint inhibition remain unproven.

Proposed Delayed Immunometabolic Amplification

The integrated hypothesis proposes that exertion-related metabolic or injury signals produce delayed immune and central symptom amplification. Specific platelet, monocyte and CSF associations exist, but a consistent post-exercise cytokine cascade and peripheral-to-central direction are not established.

Exertion-Perfusion-Muscle Immunometabolic PEM Model

Downstream

Post-Exertional Malaise Hypothesized delayed amplification of symptoms; clinical PEM is established while this molecular sequence remains unproven.

Show evidence (6 references)

PMID:38232699 SUPPORT Human Clinical

"Comparing the transcriptome at baseline and postexercise challenge, we discover patterns indicative of improper platelet activation in patients, with minimal changes elsewhere in the immune system."

Exercise-associated platelet signatures do not establish a generalized cytokine cascade or occlusive microthrombosis.

PMID:39941050 SUPPORT Human Clinical

"two independent cohorts of subjects who had lumbar puncture without exercise (non-exercise group) or after the second of two bouts of submaximal exercise performed on two consecutive days"

The CSF comparison is between independent cohorts, not paired lumbar punctures or direct muscle-to-CSF tracing.

PMID:10226888 REFUTE Human Clinical

"No group differences were seen for any of the immune variables at baseline or after exercise"

Twenty female cases and fourteen sedentary controls had serial sampling through 24 hours despite increased patient fatigue. This limits a generalized proinflammatory cytokine bridge; it does not exclude every immune mechanism.

+ 3 more references

Orthostatic Cerebral Hypoperfusion

Orthostatic challenge produces disproportionate reductions in cerebral flow or flow velocity in specialty cohorts, including some patients with normal heart-rate and blood-pressure responses. Velocity and volumetric flow are different measurements.

brain UBERON:0000955

Downstream

Orthostatic Intolerance Reduced upright cerebral perfusion is a plausible contributor to orthostatic symptoms, supported by symptom-flow associations.

Cognitive Impairment Possible contribution during upright stress; brain fog has other potential causes and is not proven to arise solely from perfusion.

Show evidence (2 references)

PMID:32140630 SUPPORT Human Clinical

"During HUT, extracranial Doppler measurements demonstrate that CBF is reduced in ME/CFS patients with POTS, dOH, and even in those without HR/BP abnormalities."

Specialty cohort of 429 cases and 44 controls; normal orthostatic heart rate and blood pressure do not exclude OI. Referral prevalence is not population prevalence.

PMID:41576003 SUPPORT Human Clinical

"reduced orthostatic CBFv (92%/88% in Long COVID/ME/CFS)"

This retrospective autonomic-referral cohort measures cerebral blood-flow velocity, not volumetric flow; it does not establish a muscle-to-brain causal pathway.

Central Motor Activation Abnormality

An older physiological study found impaired voluntary activation during sustained maximal contraction despite normal peripheral metabolism. This is a biological competing or complementary mechanism, not evidence that symptoms are voluntary or psychiatric.

brain UBERON:0000955

Downstream

Exercise Intolerance Reduced central drive can contribute to task-specific muscle performance limitations.

Show evidence (1 reference)

PMID:8423875 SUPPORT Human Clinical

This older isometric-muscle study supports altered central activation in its cohort, not a psychiatric explanation or a universal exclusion of peripheral pathology.

Possible Neuroimmune Activation

Small TSPO PET studies have conflicting findings. TSPO binding is not uniquely microglial activation, and neither generalized neuroinflammation nor a specific link from peripheral muscle signals is established.

brain UBERON:0000955

Show evidence (2 references)

PMID:24665088 SUPPORT Human Clinical

"Nine CFS/ME patients and 10 healthy controls underwent (11)C-(R)-PK11195 PET"

Small positive TSPO study; ligand binding is an indirect neuroimmune measure and does not uniquely identify activated microglia.

PMID:34815320 SUPPORT Human Clinical

"No statistically significant differences in BPND were found for patients with CFS or patients with QFS compared with HSs."

Independent study of nine women with CFS, ten with Q-fever fatigue and nine controls found no group increase; small samples and differing case definitions limit both studies.

Autophagy-Associated Macrophage Dysfunction

Atg13 gene depletion in mice disrupts autophagy and mitochondrial metabolism, promotes inflammatory macrophage polarization, and is associated with muscle nerve changes and post-treadmill weakness. This is a mechanistic model, not a validated cause of human ME/CFS or a complete model of delayed human PEM.

macrophage CL:0000235

autophagy GO:0006914

Animal models

Atg13-Depleted Mouse Mus musculus perturbs Atg13 depletion tests coupling of autophagy, macrophage activation and post-exercise muscle/nerve injury in mice.

Show evidence (1 reference)

PMID:41591477 SUPPORT Model Organism

"ablation of the atg13 gene resulted in increased infiltration of M1Mφs into the muscle vasculature, deterioration of myelin integrity in nerve bundles, and a reduction in muscle strength following treadmill exercise."

Genetically depleted mouse model supports autophagy-macrophage-muscle coupling; human ME/CFS ATG13 causation is unproven.

Proposed Peripheral Vesicle-Microglial Signaling

A 2022 study reports higher vesicle-associated serum mitochondrial DNA after exercise and microglial IL-1beta release after exposure to patient vesicle preparations. This supports a candidate peripheral inflammatory signal in vitro, without establishing which vesicle cargo is causal, a muscle source, blood-brain-barrier transport or an in vivo contribution to PEM. A matched healthy exercise series and independent donor-level bioactivity replication remain important.

Exertion-Perfusion-Muscle Immunometabolic PEM Model

Experimental models

Patient Serum Vesicle-Microglia Assay CELL LINE Adding patient vesicle preparations elicits a cultured microglial cytokine response.

Downstream

Possible Neuroimmune Activation Hypothetical extension of vesicle-preparation bioactivity to neuroimmune activation in patients. This requires biologically effective CNS exposure and in vivo confirmation; neither is demonstrated by the cultured-cell assay.

Show evidence (2 references)

PMID:36153118 SUPPORT Human Clinical

"Here, we show that mitochondrial DNA (mtDNA) associated with serum exosomes, is increased in ME/CFS patients only after exercise."

The publication reports paired patient exercise-associated change; an equivalently exercised healthy-control series is not demonstrated.

PMID:36153118 SUPPORT In Vitro

"Moreover, exosomes isolated from patients with ME/CFS stimulate significant release of IL-1β from cultured human microglia."

Patient serum vesicle preparations have in vitro bioactivity. This does not establish mtDNA necessity, muscle origin, BBB passage or human brain inflammation.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

Digestive 1

Dysphagia HP:0002015

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"reduced ability or inability to speak or swallow"

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Eye 1

Photophobia HP:0000613

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"hypersensitivity to light, sound, touch, movement, temperature extremes and smells"

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Nervous System 4

Cognitive Impairment HP:0100543

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"short-term memory problems, and difficulty concentrating or multitasking."

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Unrefreshing Sleep Non-restorative sleep HP:5200292

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"feeling exhausted, feeling flu-like and stiff on waking"

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Headache HP:0002315

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"myalgia, headaches, eye pain, abdominal pain or joint pain"

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Sound Sensitivity Phonophobia HP:0002183

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"hypersensitivity to light, sound, touch, movement, temperature extremes and smells"

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Constitutional 4

Post-Exertional Malaise OBLIGATE Postexertional symptom exacerbation HP:0030973

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"has a prolonged recovery time that may last hours, days, weeks or longer."

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Fatigue OBLIGATE HP:0012378

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"and is not significantly relieved by rest."

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Myalgia HP:0003326

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"myalgia, headaches, eye pain, abdominal pain or joint pain"

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Exercise Intolerance HP:0003546

Show evidence (4 references)

PMID:33577778 SUPPORT Human Clinical

Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.

PMID:8423875 SUPPORT Human Clinical

This older isometric-muscle study supports altered central activation in its cohort, not a psychiatric explanation or a universal exclusion of peripheral pathology.

PMID:38965566 SUPPORT Human Clinical

"Abnormal post-exertional CPET responses persisted compared to CTL matched for aerobic capacity, indicating that fitness level does not predispose to exertion intolerance in ME/CFS."

Canadian-criteria study: 84 cases and 71 sedentary controls, with 55 matched pairs; supports impaired recovery in this cohort.

+ 1 more reference

Other 3

Orthostatic Intolerance

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"including dizziness, palpitations, fainting, nausea on standing or sitting upright from a reclining position"

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Gastrointestinal Symptoms

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"gastrointestinal difficulties such as nausea, incontinence, constipation and bloating"

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

Flu-Like Symptoms

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"flu-like symptoms, including sore throat, tender glands, nausea, chills or muscle aches"

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

🧬

Genetic Associations

HLA-C (Population susceptibility association, not Mendelian causation)

Gene: HLA-C hgnc:4933

Show evidence (1 reference)

PMID:32210306 SUPPORT Human Clinical

"HLA-C*07:04 (OR 2.1 [95% CI 1.4-3.1])"

Primary high-resolution HLA association study; one ancestry cohort.

HLA-DQB1 (Population susceptibility association, not Mendelian causation)

Gene: HLA-DQB1 hgnc:4944

Show evidence (1 reference)

PMID:32210306 SUPPORT Human Clinical

"HLA-DQB1*03:03 (OR 1.5 [95% CI 1.1-2.0])"

Primary susceptibility association distinct from the prior nonspecific HLA-DRB1 attribution.

💊

Medical Actions

Individualized Energy Management

Collaborative pacing across physical, cognitive, emotional and social demands aims to reduce PEM and stabilize activity within fluctuating limits. Include planned rest and flexible adjustment; it is not a cure or a fixed upward exercise prescription. NICE advises against fixed incremental graded exercise programs.

Mechanism Target:

MODULATES Post-Exertional Malaise — Symptom-guided reduction of exertion beyond individual tolerance; supportive care rather than correction of a proven molecular lesion.

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"uses a flexible, tailored approach so that activity is never automatically increased"

NICE emphasizes individualized adjustment, not automatic progression.

Show evidence (3 references)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"uses a flexible, tailored approach so that activity is never automatically increased"

NICE emphasizes individualized adjustment, not automatic progression.

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"Do not offer people with ME/CFS:"

Negative lead-in to NICE recommendation 1.11.14, including the fixed-increment exercise item quoted below.

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"that uses fixed incremental increases in physical activity or exercise"

NICE recommendation 1.11.14 says not to offer this approach.

Sleep and Pain Management

Address sleep patterns and coexisting sleep disorders, and investigate and treat pain using individualized usual clinical care. Medication review is important because people with ME/CFS may be more intolerant of medicines; start lower and titrate when appropriate.

Show evidence (2 references)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"Investigate and manage the person's pain according to best practice"

NICE recommends symptom-focused pain care.

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"may be more intolerant of drug treatment"

NICE recommends considering lower starting doses and gradual increases.

Orthostatic Intolerance Management

Tailor nonpharmacological and, when needed, pharmacological management to the documented autonomic pattern and comorbidities. Specialist oversight is appropriate for medication and severe or worsening symptoms. An indiscriminate vasodilator is not justified by the perfusion hypothesis because low preload and high-flow impaired extraction are distinct patterns.

Show evidence (2 references)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"should only be prescribed or overseen by a healthcare professional with expertise in orthostatic intolerance."

NICE specifies expertise for OI medication.

PMID:33577778 SUPPORT Human Clinical

Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.

Severe-Disease Support and Nutrition

Offer accessible or home-based care, sensory accommodation, mobility aids, communication support, assistance with daily activities and nutrition/hydration assessment. Evaluate swallowing problems and malnutrition; oral support or enteral feeding may be required. Assess skin and immobility-related complications individually.

Show evidence (3 references)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"are unable to eat and digest food easily and may need support with hydration and nutrition"

NICE describes practical needs in severe and very severe illness.

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"oral nutrition support and enteral feeding"

NICE includes enteral support when clinically indicated.

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"areas at risk of pressure ulcers"

NICE includes skin and mobility complications in physical-function management.

Pyridostigmine

Action: Pharmacotherapy NCIT:C15986

Agent: Pyridostigmine NCIT:C47697

Investigational for ME/CFS exertional intolerance. A 45-person randomized trial found an acute relative improvement of peak VO2, cardiac output and filling pressure after one 60-mg dose, with repeat iCPET after 50 minutes. This does not establish sustained symptom or PEM benefit; the ongoing LIFT trial tests longer-term treatment.

Mechanism Target:

MODULATES Reduced Exercise Cardiac Output — Acute relative preservation of exercise cardiac output and increased filling pressure in the randomized iCPET experiment; durable symptom benefit remains unproven.

Show evidence (1 reference)

PMID:35526605 SUPPORT Human Clinical

"The peak Vo2 increased after pyridostigmine but decreased after placebo (13.3 ± 13.4 mL/min vs -40.2 ± 21.3 mL/min; P < .05)."

Randomized 45-person acute trial: 60 mg pyridostigmine between two iCPETs separated by 50 minutes improved the relative exercise response. This does not test delayed PEM or durable treatment benefit.

MODULATES Impaired Venous Return — Acute increase in filling pressure in the randomized iCPET study; this is not evidence of durable normalization of venous tone.

Show evidence (1 reference)

PMID:35526605 SUPPORT Human Clinical

"Pyridostigmine improves peak Vo2 in ME/CFS by increasing cardiac output and right ventricular filling pressures."

Acute physiological interpretation of the 45-person randomized trial; no long-term PEM outcome was tested.

Show evidence (1 reference)

PMID:35526605 SUPPORT Human Clinical

"The peak Vo2 increased after pyridostigmine but decreased after placebo (13.3 ± 13.4 mL/min vs -40.2 ± 21.3 mL/min; P < .05)."

Randomized 45-person acute trial: 60 mg pyridostigmine between two iCPETs separated by 50 minutes improved the relative exercise response. This does not test delayed PEM or durable treatment benefit.

Low-Dose Naltrexone

Action: Pharmacotherapy NCIT:C15986

Agent: Naltrexone NCIT:C62055

Investigational/off-label for ME/CFS. Ex vivo restoration of NK-cell TRPM3 activity is a mechanistic lead, not proof of clinical efficacy. LIFT studies pyridostigmine and low-dose naltrexone; a separate dose-finding trial is registered without posted outcomes as of September 2026.

Mechanism Target:

MODULATES TRPM3-Associated NK-Cell Calcium Dysregulation — Ex vivo NK-cell target modulation; not a demonstrated clinical effect of oral low-dose treatment.

Show evidence (1 reference)

PMID:31736966 SUPPORT In Vitro

"TRPM3 channel activity was restored in IL-2 stimulated NK cells isolated from ME/CFS patients after incubation for 24 h with NTX."

Eight patient and eight control donors; ex vivo rescue does not demonstrate improvement of autonomic symptoms or PEM.

Show evidence (1 reference)

PMID:31736966 SUPPORT In Vitro

"TRPM3 channel activity was restored in IL-2 stimulated NK cells isolated from ME/CFS patients after incubation for 24 h with NTX."

Eight patient and eight control donors; ex vivo rescue does not demonstrate improvement of autonomic symptoms or PEM.

Rituximab

Action: Pharmacotherapy NCIT:C15986

Agent: Rituximab NCIT:C1702

Not supported as routine ME/CFS treatment: the 151-person phase III trial found no clinical benefit over placebo. B-cell associations or an autoimmune hypothesis do not override this negative intervention result.

Show evidence (1 reference)

PMID:30934066 SUPPORT Human Clinical

"B-cell depletion using several infusions of rituximab over 12 months was not associated with clinical improvement in patients with ME/CFS."

Multicenter 151-person placebo-controlled trial did not support rituximab efficacy.

Cyclophosphamide

Action: Pharmacotherapy NCIT:C15986

Agent: Cyclophosphamide NCIT:C405

An uncontrolled 40-person study and six-year follow-up reported improvement in some participants. Lack of a randomized comparator and toxicity preclude routine use; the authors recommend restriction to clinical trials.

Show evidence (1 reference)

PMID:39042627 SUPPORT Human Clinical

"cyclophosphamide carries toxicity concerns and should not be used for ME/CFS patients outside clinical trials."

The six-year follow-up does not turn the original open-label study into a controlled efficacy result.

Plasma Exchange

Action: Plasmapheresis NCIT:C15304

Investigational: a single patient with pre-existing ME/CFS and worsening after SARS-CoV-2 infection improved following plasma exchange amid other treatment changes. This cannot establish efficacy, identify pathogenic antibodies or support routine use. Uncontrolled immunoadsorption studies likewise require randomized confirmation.

Show evidence (1 reference)

PMID:42158223 SUPPORT Human Clinical

"Our successful case highlights the need to investigate novel therapeutic approaches, including plasma exchange."

A single uncontrolled case is hypothesis-generating; receptor antibody levels did not establish a diagnostic test or causal mechanism.

🌍

Environmental Factors

Preceding Infection

ME/CFS can follow viral or nonviral infection, although onset is not always linked to an identified infection. The Dubbo prospective cohort found persistent CFS in 28 of 253 participants after EBV, Ross River virus or Coxiella burnetii infection. SARS-CoV-2 can also precede a phenotype meeting ME/CFS criteria; long COVID and ME/CFS are overlapping, not identical populations.

Show evidence (1 reference)

PMID:16950834 SUPPORT Human Clinical

"of whom 28 (11%) met the diagnostic criteria for chronic fatigue syndrome. This post-infective fatigue syndrome phenotype was stereotyped and occurred at a similar incidence after each infection."

Prospective post-infectious cohort includes a bacterial trigger; it does not estimate the proportion of all ME/CFS with infectious onset.

Exertion Beyond Individual Tolerance

Physical, cognitive, emotional and social demands can trigger or worsen PEM. Upright posture, sensory stimulation and ordinary personal care may be substantial exertion in severe disease.

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"(cognitive, physical, emotional and social)"

Energy management includes nonphysical activity as well as exercise.

Mechanism Target:

EXACERBATES Post-Exertional Malaise — Activity beyond fluctuating individual limits can provoke symptom exacerbation.

Show evidence (1 reference)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"has a prolonged recovery time that may last hours, days, weeks or longer."

NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.

🔬

Biochemical Markers

Natural Killer Cell Cytotoxicity (Variable)

Context: Candidate research phenotype; reduced on average in meta-analysis, not universal or diagnostically validated.

Show evidence (2 references)

PMID:39483457 SUPPORT Other

The meta-analysis supports reduced average cytotoxicity, with assay heterogeneity; it is not a universal individual diagnostic marker.

PMID:31057538 SUPPORT Human Clinical

"Contrary to previous reports, no significant differences were observed in NK cell numbers, subtype proportions or in vitro responsiveness between ME/CFS patients and healthy control participants."

The 251-case biobank study, including 54 severe cases, did not reproduce these NK abnormalities; its assays and sample handling differ from cytotoxicity studies.

Cytokine Profiles (Variable)

Context: Case definition, sex, illness duration, severity, assays and timing influence results. Cross-sectional severity associations do not establish an early-disease or post-exercise cytokine surge.

Show evidence (2 references)

PMID:10226888 SUPPORT Human Clinical

"No group differences were seen for any of the immune variables at baseline or after exercise"

Twenty female cases and fourteen sedentary controls had serial sampling through 24 hours despite increased patient fatigue.

PMID:24027260 SUPPORT Human Clinical

"We found that these environmental manipulations did not produce clinically significant upregulation of proinflammatory cytokines."

Repeated sampling after exercise and sleep deprivation did not support a generalized proinflammatory cytokine response.

Plasma and Urine Metabolomic Profiles (Variable)

Context: Purine, lipid and other concentration differences are research findings. Neither a uniform hypermetabolic nor hypometabolic state, diagnostic classifier or proven muscle-source signal is established.

Show evidence (2 references)

PMID:31277442 SUPPORT Human Clinical

"The principal biochemical change related to the 7-day severity of PEM was the fall in the purine metabolite, hypoxanthine."

Forty-seven cases reported recent PEM severity; a seven-day symptom window is not a serial provoked exercise experiment or a direct measurement of metabolic flux.

PMID:27573827 SUPPORT Human Clinical

"Eighty percent of the diagnostic metabolites were decreased, consistent with a hypometabolic syndrome."

The study had 45 cases and 39 controls, 84 total. Concentration profiles and internal classification do not establish organism-wide metabolic shutdown or a validated diagnostic test.

Muscle Tissue Sodium (Elevated in a small pilot cohort)

Context: Research 23Na-MRI finding in six female cases; compartment mixing prevents equating it with intracellular sodium or calcium overload.

Show evidence (1 reference)

PMID:36494667 SUPPORT Human Clinical

"Baseline tissue sodium content was higher in all 5 lower leg muscle compartments in ME/CFS compared to controls."

Six female cases and six matched controls underwent sodium MRI before and after three minutes of plantar flexion. The acquisition could not isolate intracellular from extracellular sodium.

🔬

Diagnosis

Clinical Symptom and Functional Assessment

Document pre-illness function, the delayed response to physical and cognitive activity, sleep, cognition, upright symptoms and duration. A symptom/activity diary can help. CDC/NAM-style criteria require at least six months of substantial functional impairment with fatigue, PEM and unrefreshing sleep, plus cognitive impairment or orthostatic intolerance (or both). NICE permits diagnosis after three months and requires all four domains: debilitating fatigue, PEM, unrefreshing sleep or sleep disturbance, and cognitive difficulties; OI is an additional feature. In either approach assess other explanations and coexisting conditions, and start symptom care while evaluation continues.

Show evidence (2 references)

url:https://www.cdc.gov/me-cfs/hcp/diagnosis/index.html SUPPORT Other

"A thorough medical history, physical (including neurological) and mental health exam, and laboratory testing should be performed."

CDC diagnostic approach requires clinical assessment and differential evaluation; the adjacent symptom list specifies PEM, sleep and cognitive/orthostatic features.

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"that have persisted for 3 months and are not explained by another condition."

NICE diagnostic duration differs from the NAM-style six-month threshold.

Evaluation for Alternative and Coexisting Conditions

Use history, examination and targeted investigations rather than a universal exhaustive test panel. NICE examples include urinalysis, blood count, electrolytes, liver and thyroid tests, inflammatory markers, calcium/phosphate, HbA1c, ferritin, coeliac screening and creatine kinase; add B12/folate, vitamin D, infection tests or morning cortisol when indicated. Evaluate sleep disorders, medication effects, anemia, endocrine, inflammatory, neuromuscular and mental-health conditions as appropriate; comorbidities can coexist with ME/CFS.

Show evidence (2 references)

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations SUPPORT Other

"investigations to exclude other diagnoses"

NICE lists baseline investigations and clinical-judgment additions.

url:https://www.cdc.gov/me-cfs/hcp/diagnosis/index.html SUPPORT Other

"These steps are crucial to evaluate for other conditions that may explain symptoms."

Differential assessment precedes diagnosis and continues during follow-up.

Orthostatic Assessment

Record upright symptoms and heart rate/blood pressure, using an adapted standing or specialist tilt assessment when clinically indicated and tolerated. Normal HR/BP does not rule out OI. Doppler cerebral-flow assays are research/specialist methods, not mandatory diagnostic tests.

Show evidence (2 references)

PMID:32140630 SUPPORT Human Clinical

"During HUT, extracranial Doppler measurements demonstrate that CBF is reduced in ME/CFS patients with POTS, dOH, and even in those without HR/BP abnormalities."

Specialty cohort of 429 cases and 44 controls; normal orthostatic heart rate and blood pressure do not exclude OI. Referral prevalence is not population prevalence.

PMID:41576003 SUPPORT Human Clinical

"reduced orthostatic CBFv (92%/88% in Long COVID/ME/CFS)"

This retrospective autonomic-referral cohort measures cerebral blood-flow velocity, not volumetric flow; it does not establish a muscle-to-brain causal pathway.

Biomarker and Exercise-Test Limitations

There is no confirmatory blood, imaging, genetic or exercise test. NK function, cytokines, metabolomics, sodium MRI and commercial ATP profiles are not established diagnostic assays. Two-day CPET can characterize impairment in selected research or specialist settings but is not required for diagnosis; it can provoke prolonged worsening, especially in severe disease, and a negative day-two decline does not exclude PEM.

Show evidence (4 references)

url:https://www.cdc.gov/me-cfs/hcp/diagnosis/index.html SUPPORT Other

"There is no confirmatory test currently available to diagnose ME/CFS."

CDC distinguishes biological abnormalities from diagnostic validation.

PMID:31391529 SUPPORT Human Clinical

"The MES test does not have the reliability and reproducibility required of a diagnostic test and therefore should not currently be offered as a diagnostic test for CFS/ME."

Independent ten-case/thirteen-control replication failed; sample-processing delay substantially affected the score.

PMID:38965566 SUPPORT Human Clinical

"Abnormal post-exertional CPET responses persisted compared to CTL matched for aerobic capacity, indicating that fitness level does not predispose to exertion intolerance in ME/CFS."

Canadian-criteria study: 84 cases and 71 sedentary controls, with 55 matched pairs; supports impaired recovery in this cohort.

+ 1 more reference

Longitudinal Review

Review symptoms, nutrition, function, medication effects and coexisting conditions regularly, adapting access to severity. Investigate new or changing symptoms rather than attributing every finding to ME/CFS.

Show evidence (1 reference)

url:https://www.cdc.gov/me-cfs/hcp/diagnosis/index.html SUPPORT Other

"Patients with ME/CFS should be re-evaluated periodically."

Continued assessment and usual preventive care remain appropriate.

📊

Related Datasets

Circulating cell-free RNA signatures for the characterization and diagnosis of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) geo:GSE293840

People living with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) experience heterogeneous and debilitating symptoms that lack sufficient biological explanation, compounded by the absence of accurate, noninvasive diagnostic tools. To address these challenges, we explored circulating cell-free RNA (cfRNA) as a blood-borne bioanalyte to monitor ME/CFS. cfRNA is released into the bloodstream during cellular turnover and reflects dynamic changes in gene expression, cellular signaling, and tissue-specific processes.

human BULK RNA SEQ n=168

PMID:40789036

Identified by GEO DataSets index search for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-07-31. Title, sample count, and organism are GEO's own values. Accession reverified on 2026-09-04. Dataset records or repeated samples are not necessarily independent participants. Provider-report citation does not establish that OpenScientist downloaded or analyzed this dataset.

Sex-Dependent Transcriptional Changes in response to stress in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome geo:GSE227375

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex, multi-symptom illness characterized by debilitating fatigue and post-exertional malaise (PEM). Numerous studies have reported sex differences at the epidemiological, cellular, and molecular levels between male and female ME/CFS patients. To gain further insight into these sex-dependent changes, we evaluated differential gene expression by RNA-sequencing in 35 ME/CFS patients (24 female, 11 male) and 34 matched healthy control participants (21 female and 13 male) during and after an exercise challenge intended to provoke PEM.

human BULK RNA SEQ n=187

PMID:37373402

Genome-epigenome interactions associated with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome geo:GSE156792

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex disease of unknown etiology. Multiple studies point to disruptions in immune functioning in ME/CFS patients as well as specific genetic polymorphisms and alterations of the DNA methylome in lymphocytes. However, potential interactions between DNA methylation and genetic background in relation to ME/CFS have not been examined. In this study we explored this association by characterizing the epigenetic (~480 thousand CpG loci) and genetic (~4.3 million SNPs) variation between cohorts of ME/CFS patients and healthy controls.

human METHYLATION n=109

PMID:30516085

Insights into myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) phenotypes through comprehensive metabolomics metabolomics_workbench:ST000800

Located via OmicsDI, which aggregates across omics repositories; this record comes from metabolomics_workbench. Only repositories with no other discovery route in this project and with a working accession resolver are curated from OmicsDI -- GEO, ArrayExpress, PRIDE, MetaboLights and EGA hits are excluded as duplicates of dedicated passes. Matched because the disease is named in the dataset's own title ("Myalgic Encephalomyelitis/Chronic Fatigue Syndrome"). Retrieved 2026-08-02. Accession reverified on 2026-09-04. Dataset records or repeated samples are not necessarily independent participants. Provider-report citation does not establish that OpenScientist downloaded or analyzed this dataset.

Insights into myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) phenotypes through comprehensive metabolomics (part IV) metabolomics_workbench:ST000813

Insights into myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) phenotypes through comprehensive metabolomics (part III)) metabolomics_workbench:ST000802

🔬

Clinical Trials

NCT06366724 PHASE_II RECRUITING

LIFT: Life Improvement Trial

Show evidence (1 reference)

clinicaltrials:NCT06366724 SUPPORT Other

"The LIFT will be conducted at Brigham and Women's Hospital (BWH) of Harvard Medical School, focusing on the effect of Pyridostigmine (Mestinon) and Low-Dose Naltrexone (LDN) in subjects aged 18-70 meeting the Canadian consensus criteria (CCC) for Myalgic Encephalomyelitis/Chronic Fatigue..."

Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.

NCT03674541 PHASE_II COMPLETED

The Exercise Response to Pharmacologic Cholinergic Stimulation in Myalgic Encephalomyelitis / Chronic Fatigue Syndrome

Show evidence (1 reference)

clinicaltrials:NCT03674541 SUPPORT Other

"Myalgic encephalomyelitis/Chronic fatigue syndrome (ME/CFS), otherwise known as Chronic fatigue syndrome (CFS) or myalgic encephalomyelitis (ME), is an under-recognized disorder whose cause is not yet understood."

Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.

NCT07285473 PHASE_II NOT_RECRUITING

Low-Dose Naltrexone For ME/CFS: Dose-Finding

Show evidence (1 reference)

clinicaltrials:NCT07285473 SUPPORT Other

"This exploratory clinical trial tests low-dose naltrexone (LDN) for the treatment of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)."

Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.

NCT02229942 PHASE_III COMPLETED

B-lymphocyte Depletion Using Rituximab in Chronic Fatigue Syndrome/ Myalgic Encephalopathy (CFS/ME). A Randomized Phase-III Study.

Show evidence (1 reference)

clinicaltrials:NCT02229942 SUPPORT Other

"The hypothesis is that a subgroup of patients with Chronic Fatigue Syndrome/ Myalgic Encephalopathy (CFS/ME) have a chronically activated immune system and may benefit from B-lymphocyte treatment using the monoclonal anti-CD20 antibody rituximab with induction and maintenance treatment."

Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.

NCT02444091 PHASE_II COMPLETED

Cyclophosphamide in Myalgic Encephalopathy/ Chronic Fatigue Syndrome (ME/CFS)

Show evidence (1 reference)

clinicaltrials:NCT02444091 SUPPORT Other

"Significant clinical improvements of ME/CFS symptoms were observed in two patients with long-standing ME/CFS who received adjuvant chemotherapy including cyclophosphamide for breast cancer, also in one ME/CFS patient who received chemotherapy including iphosphamide for Hodgkin lymphoma."

Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.

NCT04026425 NOT_APPLICABLE COMPLETED

Analysis of Post-exertional Malaise Using a Two-day CPET in People With ME/CFS

Show evidence (1 reference)

clinicaltrials:NCT04026425 SUPPORT Other

"This study aims to collect and identify key outcome measures or disease parameters in ME/CFS that are altered during elevated symptoms relative to baseline by gathering information before and after symptom provocation using a two-day cardiopulmonary exercise test."

Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.

🧫

Experimental Models

Patient-Derived Skeletal Myotubes PRIMARY_CELL_CULTURE

Nine CFS and eleven control donors; glucose-linked oxidative metabolism differed while galactose and fatty-acid use were preserved. Culture retention does not distinguish genetic from persistent epigenetic effects.

Organism

Homo sapiens NCBITaxon:9606

Pathograph links

Skeletal Muscle Bioenergetic Disturbance measures Patient-derived myotubes show impaired glucose oxidation with preserved galactose and fatty-acid oxidation in substrate-specific culture assays.

Show evidence (1 reference)

PMID:33106563 SUPPORT In Vitro

"galactose and fatty acids normally, indicating that the bioenergetic dysfunction lies upstream of the TCA cycle."

Cultured myotubes from nine CFS and eleven control donors had substrate-dependent glucose-use abnormalities; persistence in culture is not proof of a genetic defect.

Show evidence (1 reference)

PMID:33106563 SUPPORT In Vitro

"galactose and fatty acids normally, indicating that the bioenergetic dysfunction lies upstream of the TCA cycle."

Cultured myotubes from nine CFS and eleven control donors had substrate-dependent glucose-use abnormalities; persistence in culture is not proof of a genetic defect.

Patient NK-Cell TRPM3 Assays PRIMARY_CELL_CULTURE

Electrophysiology with pregnenolone sulfate, ononetin and naltrexone; later live-cell cytosolic/mitochondrial calcium assays. Ex vivo target modulation is not clinical drug efficacy.

Organism

Homo sapiens NCBITaxon:9606

Pathograph links

TRPM3-Associated NK-Cell Calcium Dysregulation measures Patch-clamp and compartment-specific calcium measurements identify condition-dependent NK-cell abnormalities; IL-2/naltrexone experiments test ex vivo channel rescue.

Show evidence (2 references)

PMID:31736966 SUPPORT In Vitro

"TRPM3 channel activity was restored in IL-2 stimulated NK cells isolated from ME/CFS patients after incubation for 24 h with NTX."

Eight patient and eight control donors; ex vivo rescue does not demonstrate improvement of autonomic symptoms or PEM.

+ 1 more reference

Show evidence (2 references)

PMID:31736966 SUPPORT In Vitro

"TRPM3 channel activity was restored in IL-2 stimulated NK cells isolated from ME/CFS patients after incubation for 24 h with NTX."

Eight patient and eight control donors; ex vivo rescue does not demonstrate improvement of autonomic symptoms or PEM.

PMID:42177403 SUPPORT In Vitro

Patient T-Cell Metabolic Assays PRIMARY_CELL_CULTURE

Resting and activated CD4/CD8 cells from 53 cases and 45 controls; glycolytic flux and membrane-potential assays.

Organism

Homo sapiens NCBITaxon:9606

Pathograph links

T-Cell Immunometabolic Dysfunction measures Resting CD4/CD8 and activated CD8 assays measure reduced glycolysis in patient cells; this does not establish global respiratory failure.

Show evidence (1 reference)

PMID:31830003 SUPPORT In Vitro

"Both CD4+ and CD8+ T cells from patients with ME/CFS had reduced glycolysis at rest, whereas CD8+ T cells also had reduced glycolysis following activation."

Primary patient-cell metabolism study with 53 cases and 45 controls; this does not establish universal mitochondrial respiratory failure.

Show evidence (1 reference)

PMID:31830003 SUPPORT In Vitro

"Both CD4+ and CD8+ T cells from patients with ME/CFS had reduced glycolysis at rest, whereas CD8+ T cells also had reduced glycolysis following activation."

Primary patient-cell metabolism study with 53 cases and 45 controls; this does not establish universal mitochondrial respiratory failure.

Erythrocyte Microfluidic Deformability Assay OTHER

Sixteen case-control pairs studied outside the body; channel transit measures do not establish in vivo capillary obstruction.

Organism

Homo sapiens NCBITaxon:9606

Pathograph links

Reduced Erythrocyte Deformability measures Microfluidic transit assays measure altered deformability of patient erythrocytes.

Show evidence (1 reference)

PMID:30594919 SUPPORT In Vitro

"We observed from various measures of deformability that the RBCs isolated from ME/CFS patients were significantly stiffer than those from healthy controls."

Sixteen case-control pairs tested in a microfluidic device; the proposed in vivo perfusion consequence and diagnostic performance remain unvalidated.

Show evidence (1 reference)

PMID:30594919 SUPPORT In Vitro

"We observed from various measures of deformability that the RBCs isolated from ME/CFS patients were significantly stiffer than those from healthy controls."

Sixteen case-control pairs tested in a microfluidic device; the proposed in vivo perfusion consequence and diagnostic performance remain unvalidated.

Patient Serum Vesicle-Microglia Assay CELL_LINE

Human HM-SV40 microglia exposed to patient serum extracellular-vesicle preparations, with IL-1beta release as a readout. Published abstract and figure captions support bioactivity; detailed pooling/isolation information is available in the earlier author preprint, and final-version full methods were not accessible. Cargo identity, muscle origin and BBB crossing were not established.

Organism

Homo sapiens NCBITaxon:9606

Pathograph links

Proposed Peripheral Vesicle-Microglial Signaling perturbs Adding patient vesicle preparations elicits a cultured microglial cytokine response.

Limitations: An immortalized cell assay does not reproduce brain exposure in vivo. Vesicle-preparation effects do not isolate mtDNA from other cargo or copurified material.

Show evidence (1 reference)

PMID:36153118 SUPPORT In Vitro

"Moreover, exosomes isolated from patients with ME/CFS stimulate significant release of IL-1β from cultured human microglia."

Patient serum vesicle preparations have in vitro bioactivity. This does not establish mtDNA necessity, muscle origin, BBB passage or human brain inflammation.

Show evidence (1 reference)

PMID:36153118 SUPPORT In Vitro

"Moreover, exosomes isolated from patients with ME/CFS stimulate significant release of IL-1β from cultured human microglia."

Patient serum vesicle preparations have in vitro bioactivity. This does not establish mtDNA necessity, muscle origin, BBB passage or human brain inflammation.

🐁

Animal Models

Atg13-Depleted Mouse

Heterozygous Atg13 depletion connects impaired autophagy, oxidative metabolism, macrophage polarization and muscle-nerve abnormalities. Treadmill weakness does not establish human symptom-defined PEM, disease-specific genetics or the full perfusion pathway.

Species

Mus musculus

Genotype

Tg+/-ATG13

Publication

PMID:41591477

Pathograph links

Autophagy-Associated Macrophage Dysfunction perturbs Atg13 depletion tests coupling of autophagy, macrophage activation and post-exercise muscle/nerve injury in mice.

Show evidence (1 reference)

PMID:41591477 SUPPORT Model Organism

Genetically depleted mouse model supports autophagy-macrophage-muscle coupling; human ME/CFS ATG13 causation is unproven.

Show evidence (1 reference)

PMID:41591477 SUPPORT Model Organism

Genetically depleted mouse model supports autophagy-macrophage-muscle coupling; human ME/CFS ATG13 causation is unproven.

{ }

Source YAML

click to show

name: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome
creation_date: '2025-12-06T01:38:31Z'
description: >-
  ME/CFS is a chronic, fluctuating multisystem illness defined by substantial loss of previous function,
  post-exertional symptom exacerbation, unrefreshing sleep, and cognitive or orthostatic symptoms.
  Infection can precede onset, but no single cause, diagnostic biomarker or disease-modifying treatment
  is established. Neurovascular, immune, metabolic and central abnormalities vary by cohort; the
  integrated mechanism of delayed PEM remains unresolved.
category: Complex
parents:
- Neurological Disorder
- Immune Disorder
disease_term:
  preferred_term: myalgic encephalomyelitis
  term:
    id: MONDO:0005404
    label: myalgic encephalomeyelitis/chronic fatigue syndrome
synonyms:
- ME/CFS
- Chronic Fatigue Syndrome
- Systemic Exertion Intolerance Disease
pathophysiology:
- name: Small-Fiber Neuropathy
  description: Reduced epidermal small-fiber density occurs in a subset of selected patients. Autonomic small-fiber dysfunction could affect venous tone or distribution of muscle blood flow, but skin-fiber density does not directly establish either mechanism.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:33577778
    reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Among the 160 ME/CFS patient biopsies, 31% were consistent with SFN (epidermal innervation ≤5.0% of predicted; P < .0001). Denervation severity did not correlate with exertional measures.
    explanation: The ME/CFS biopsy proportion was 31%, not the report's approximately 50%; the latter is background POTS/fibromyalgia literature. A shunting mechanism is proposed rather than causally demonstrated.
  downstream:
  - target: Impaired Venous Return
    description: Proposed loss of effective venoconstriction could reduce cardiac return. The pathway was not directly demonstrated, and biopsy denervation severity did not correlate with exertional measures.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:33577778
      reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Distal degeneration (axonopathy) can impair venoconstriction with resultant peripheral blood pooling decreasing cardiac return, consistent with the “low-flow preload failure” we identified.
      explanation: The authors propose this route from clinical exercise physiology and prior autonomic-neuropathy evidence. They did not directly demonstrate the causal connection or find a correlation between biopsy denervation severity and exertional measures.
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
  - target: Impaired Peripheral Oxygen Extraction
    description: Proposed microvascular shunting; the mechanism remains inferred from physiology, without direct capillary shunt imaging.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:33577778
      reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: In patients with small-fiber pathology, neuropathic dysregulation causing microvascular dilation may limit exertion by shunting oxygenated blood from capillary beds and reducing cardiac return.
      explanation: The authors propose this route from clinical exercise physiology and prior autonomic-neuropathy evidence. They did not directly demonstrate the causal connection or find a correlation between biopsy denervation severity and exertional measures.
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
- name: Impaired Venous Return
  description: Low cardiac filling pressure is present in the selected iCPET cohort. Low right-atrial pressure was an inclusion criterion, so this finding cannot establish its frequency throughout ME/CFS.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:33577778
    reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction.
    explanation: 'Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.'
  downstream:
  - target: Reduced Exercise Cardiac Output
    description: Impaired filling limits cardiac output during upright exertion in the low-flow phenotype.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:33577778
      reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction.
      explanation: 'Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.'
    intermediate_mechanisms:
    - Reduced ventricular filling and stroke volume
- name: Reduced Exercise Cardiac Output
  description: The low-flow subgroup has reduced exercise cardiac output, limiting oxygen delivery. It is distinct from the high-flow oxygen-extraction phenotype.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:33577778
    reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction.
    explanation: 'Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.'
  - reference: PMID:35526605
    reference_title: 'Neurovascular Dysregulation and Acute Exercise Intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Randomized, Placebo-Controlled Trial of Pyridostigmine.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The peak Vo2 increased after pyridostigmine but decreased after placebo (13.3 ± 13.4 mL/min vs -40.2 ± 21.3 mL/min; P < .05).
    explanation: 'Randomized 45-person acute trial: 60 mg pyridostigmine between two iCPETs separated by 50 minutes improved the relative exercise response. This does not test delayed PEM or durable treatment benefit.'
  downstream:
  - target: Exercise Intolerance
    description: Reduced exercise oxygen delivery contributes to limited aerobic capacity in this physiological subgroup.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:33577778
      reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction.
      explanation: 'Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.'
- name: Impaired Peripheral Oxygen Extraction
  description: High-flow patients have reduced systemic oxygen extraction despite preserved flow. Maldistributed flow and cellular oxygen use are candidate explanations; impaired extraction is not equivalent to reduced total limb perfusion.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:33577778
    reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction.
    explanation: 'Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.'
  downstream:
  - target: Exercise Intolerance
    description: Reduced extraction limits usable oxygen during exertion in this selected subgroup.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:33577778
      reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction.
      explanation: 'Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.'
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
  - target: Skeletal Muscle Bioenergetic Disturbance
    description: The proposed link from oxygen-use limitation to myocyte metabolic disturbance has not been tested with simultaneous patient-level perfusion and muscle assays.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:33577778
      reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction.
      explanation: 'Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.'
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
- name: Endothelial Vasodilator Dysfunction
  description: Reduced brachial flow-mediated dilation and skin reactive hyperemia indicate vascular dysfunction in some cohorts. These measurements do not directly demonstrate capillary obstruction or muscle ischemia.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:36730360
    reference_title: Endothelial dysfunction in ME/CFS patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: ME/CFS patients had markedly reduced FMD compared to healthy controls at baseline (5.1% vs. 8.2%, p< 0.0001, adjusted for arterial diameter and sex), and significantly lower microvascular regulation measured by PORH than healthy controls (1354 PU vs. 2208 PU, p = 0.002).
    explanation: Sandvik and colleagues studied 39 RituxME participants; macrovascular FMD and skin PORH are distinct from direct exercising-muscle perfusion. The two measures did not correlate.
  downstream:
  - target: Skeletal Muscle Bioenergetic Disturbance
    description: Possible impaired delivery to exercising muscle; the FMD/PORH study did not establish this causal bridge.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:36730360
      reference_title: Endothelial dysfunction in ME/CFS patients.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: ME/CFS patients had markedly reduced FMD compared to healthy controls at baseline (5.1% vs. 8.2%, p< 0.0001, adjusted for arterial diameter and sex), and significantly lower microvascular regulation measured by PORH than healthy controls (1354 PU vs. 2208 PU, p = 0.002).
      explanation: Sandvik and colleagues studied 39 RituxME participants; macrovascular FMD and skin PORH are distinct from direct exercising-muscle perfusion. The two measures did not correlate.
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
  cell_types:
  - preferred_term: endothelial cell
    term:
      id: CL:0000115
      label: endothelial cell
  biological_processes:
  - preferred_term: vasodilation
    term:
      id: GO:0042311
      label: vasodilation
- name: Reduced Erythrocyte Deformability
  description: Patient erythrocytes had lower deformability in a small microfluidic study. This has not established in vivo capillary plugging, thrombosis, or a clinical diagnostic assay.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:30594919
    reference_title: Red blood cell deformability is diminished in patients with Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: We observed from various measures of deformability that the RBCs isolated from ME/CFS patients were significantly stiffer than those from healthy controls.
    explanation: Sixteen case-control pairs tested in a microfluidic device; the proposed in vivo perfusion consequence and diagnostic performance remain unvalidated.
  cell_types:
  - preferred_term: erythrocyte
    term:
      id: CL:0000232
      label: erythrocyte
  downstream:
  - target: Myalgia
    description: Hypothetical symptom contribution through impaired microvascular perfusion and tissue oxygenation, as proposed by the assay authors; in vivo perfusion and symptom mediation remain untested.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
    evidence:
    - reference: PMID:30594919
      reference_title: Red blood cell deformability is diminished in patients with Chronic Fatigue Syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: We speculate that the larger and less deformable RBCs in ME/CFS patients may partly explain the musculoskeletal pain and fatigue
      explanation: The authors explicitly speculate about symptoms through impaired microvascular perfusion and tissue oxygenation. The microfluidic assay did not measure in vivo delivery, systemic oxygen extraction or causal symptom mediation.
  - target: Fatigue
    description: Hypothetical symptom contribution through impaired microvascular perfusion and tissue oxygenation, as proposed by the assay authors; in vivo perfusion and symptom mediation remain untested.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
    evidence:
    - reference: PMID:30594919
      reference_title: Red blood cell deformability is diminished in patients with Chronic Fatigue Syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: We speculate that the larger and less deformable RBCs in ME/CFS patients may partly explain the musculoskeletal pain and fatigue
      explanation: The authors explicitly speculate about symptoms through impaired microvascular perfusion and tissue oxygenation. The microfluidic assay did not measure in vivo delivery, systemic oxygen extraction or causal symptom mediation.
- name: Skeletal Muscle Bioenergetic Disturbance
  description: Muscle studies suggest substrate-specific metabolic abnormalities and heterogeneous structural findings. In vitro glucose oxidation, cross-sectional EM and long-COVID paired biopsies address different questions. Neither universal fatty-acid oxidation failure nor a single primary mitochondrial lesion is established.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:33106563
    reference_title: Substrate utilisation of cultured skeletal muscle cells in patients with CFS.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: galactose and fatty acids normally, indicating that the bioenergetic dysfunction lies upstream of the TCA cycle.
    explanation: Cultured myotubes from nine CFS and eleven control donors had substrate-dependent glucose-use abnormalities; persistence in culture is not proof of a genetic defect.
  - reference: PMID:38338957
    reference_title: Functional and Morphological Differences of Muscle Mitochondria in Chronic Fatigue Syndrome and Post-COVID Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Due to the lack of an EM control group, the mean size and shape of CFS and PCS can only be compared between the respective syndromes.
    explanation: The direct 2024 study compared mitochondrial ultrastructure in 14 CFS and 14 PCS samples without healthy EM controls. OXPHOS used historical healthy controls; between-syndrome morphology does not prove calcium-mediated injury.
  - reference: PMID:9527150
    reference_title: Muscle fibre characteristics and lactate responses to exercise in chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: No significant ultrastructural abnormalities were found.
    explanation: An older 105-case biopsy study examined 41 samples by EM; findings qualify a universal structural mitochondrial lesion.
  - reference: PMID:38177128
    reference_title: Muscle abnormalities worsen after post-exertional malaise in long COVID.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We conclude that amyloid-containing deposits are not present within capillaries.
    explanation: The 25-person long-COVID PEM cohort and 21 recovered controls had paired biopsies. Deposits were extravascular; this contradicts equating the observation with occlusive muscle microclots.
  - reference: PMID:38177128
    reference_title: Muscle abnormalities worsen after post-exertional malaise in long COVID.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Oxidative phosphorylation capacity decreased one day following the maximal exercise in both controls and patients
    explanation: A paired long-COVID exercise study supports muscle abnormalities, but this shared respiratory decrease alone is not a case-specific effect or proof of the complete ME/CFS chain.
  downstream:
  - target: Proposed Delayed Immunometabolic Amplification
    description: Proposed muscle metabolite or injury signals could amplify delayed symptoms. No source-to-target tracing or integrated perturbation demonstrates this step.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:39240417
      reference_title: 'Towards an understanding of physical activity-induced post-exertional malaise: Insights into microvascular alterations and immunometabolic interactions in post-COVID condition and myalgic encephalomyelitis/chronic fatigue syndrome.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: The accumulation of molecules such as lactate, reactive oxygen species or prostaglandins might trigger local and systemic immune activation. Subsequent intensification of bioenergetic inflexibilities, muscular ionic disturbances and modulation of central nervous system functions can lead to an exacerbation of existing pathologies and symptoms.
      explanation: Narrative review explicitly proposes the integrated metabolic/immune/CNS sequence; it is not direct causal validation.
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
  cell_types:
  - preferred_term: cell of skeletal muscle
    term:
      id: CL:0000188
      label: cell of skeletal muscle
  biological_processes:
  - preferred_term: oxidative phosphorylation
    term:
      id: GO:0006119
      label: oxidative phosphorylation
- name: Elevated Skeletal Muscle Tissue Sodium
  description: A 2022 pilot found higher MRI tissue sodium at rest and after brief exercise. Echo-time and compartment mixing prevent interpreting the signal as a direct measure of intracellular sodium or calcium overload.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:36494667
    reference_title: Muscle sodium content in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Baseline tissue sodium content was higher in all 5 lower leg muscle compartments in ME/CFS compared to controls.
    explanation: Six female cases and six matched controls underwent sodium MRI before and after three minutes of plantar flexion. The acquisition could not isolate intracellular from extracellular sodium.
  cell_types:
  - preferred_term: cell of skeletal muscle
    term:
      id: CL:0000188
      label: cell of skeletal muscle
  biological_processes:
  - preferred_term: muscle tissue sodium homeostasis
    term:
      id: GO:0055078
      label: sodium ion homeostasis
    modifier: DYSREGULATED
  downstream:
  - target: Proposed Muscle Sodium-Calcium Loading
    description: 'Hypothetical interpretation: if elevated tissue sodium includes sufficiently elevated myocyte sodium, exchanger reversal could promote calcium loading. MRI compartment mixing and the absence of direct calcium measurements leave this transition unverified.'
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
    evidence:
    - reference: PMID:36494667
      reference_title: Muscle sodium content in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: High intracellular sodium can reverse the transport direction of the sodium–calcium exchanger (NCX) to import calcium instead of exporting
      explanation: The authors propose exchanger reversal in their discussion; the patient MRI measurement does not resolve compartments. The edge is conditional on an intracellular component and does not convert tissue sodium into demonstrated myocyte sodium or calcium overload.
- name: Proposed Muscle Sodium-Calcium Loading
  description: The NHE1 sodium-loading, reduced Na/K-pump activity and reversed sodium/calcium-exchanger model predicts calcium-mediated mitochondrial injury. The sodium MRI pilot does not isolate intracellular sodium; direct human muscle calcium overload and exchanger reversal remain unverified.
  mechanism_confidence: HYPOTHETICAL
  evidence:
  - reference: PMID:39727052
    reference_title: 'Key Pathophysiological Role of Skeletal Muscle Disturbance in Post COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Accumulated Evidence.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: The sodium‐calcium exchanger (NCX) changes into reverse transport mode importing calcium instead of exporting it
    explanation: This is a proposed mechanism in a narrative review, not a direct human measurement.
  - reference: PMID:36494667
    reference_title: Muscle sodium content in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Baseline tissue sodium content was higher in all 5 lower leg muscle compartments in ME/CFS compared to controls.
    explanation: Six female cases and six matched controls underwent sodium MRI before and after three minutes of plantar flexion. The acquisition could not isolate intracellular from extracellular sodium.
  downstream:
  - target: Skeletal Muscle Bioenergetic Disturbance
    description: Predicted calcium toxicity to myocytes and mitochondria; retain as a hypothetical link requiring compartment-specific measurement and perturbation.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:39727052
      reference_title: 'Key Pathophysiological Role of Skeletal Muscle Disturbance in Post COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Accumulated Evidence.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: we postulated that hypoperfusion and ischemia can result in excessive sodium and calcium overload in skeletal muscles of ME/CFS patients to cause mitochondrial damage.
      explanation: Explicit mechanistic hypothesis in a review; the MRI pilot does not directly demonstrate intracellular calcium toxicity.
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
- name: Purine and Systemic Metabolite Alterations
  description: Lower plasma hypoxanthine correlates with recent PEM severity. Broad plasma metabolomic differences vary by sex and cohort; concentrations do not prove flux, whole-body hypermetabolism, muscle source or dauer-like causation.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:31277442
    reference_title: Post-Exertional Malaise Is Associated with Hypermetabolism, Hypoacetylation and Purine Metabolism Deregulation in ME/CFS Cases.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The principal biochemical change related to the 7-day severity of PEM was the fall in the purine metabolite, hypoxanthine.
    explanation: Forty-seven cases reported recent PEM severity; a seven-day symptom window is not a serial provoked exercise experiment or a direct measurement of metabolic flux.
  - reference: PMID:27573827
    reference_title: Metabolic features of chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Eighty percent of the diagnostic metabolites were decreased, consistent with a hypometabolic syndrome.
    explanation: The study had 45 cases and 39 controls, 84 total. Concentration profiles and internal classification do not establish organism-wide metabolic shutdown or a validated diagnostic test.
  biological_processes:
  - preferred_term: purine nucleotide metabolic process
    term:
      id: GO:0006163
      label: purine nucleotide metabolic process
- name: Classical Monocyte State Dysregulation
  description: Single-cell profiles indicate altered differentiation and migration programs at baseline, including heterogeneous cell states within patients. Actual tissue invasion is not demonstrated by these data.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:38232699
    reference_title: Single-cell transcriptomics of the immune system in ME/CFS at baseline and following symptom provocation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: At baseline, ME/CFS patients display classical monocyte dysregulation suggestive of inappropriate differentiation and migration to tissue.
    explanation: Single-cell transcriptional association; actual tissue migration and its causal contribution to PEM were not directly measured.
  cell_types:
  - preferred_term: classical monocyte
    term:
      id: CL:0000860
      label: classical monocyte
- name: Post-Exertional Platelet Transcriptional Dysregulation
  description: Exercise-associated platelet activation signatures provide a specific immune-vascular observation. They do not establish widespread occlusive microclots or a generalized cytokine surge.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:38232699
    reference_title: Single-cell transcriptomics of the immune system in ME/CFS at baseline and following symptom provocation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Comparing the transcriptome at baseline and postexercise challenge, we discover patterns indicative of improper platelet activation in patients, with minimal changes elsewhere in the immune system.
    explanation: Exercise-associated platelet signatures do not establish a generalized cytokine cascade or occlusive microthrombosis.
  cell_types:
  - preferred_term: platelet
    term:
      id: CL:0000233
      label: platelet
  biological_processes:
  - preferred_term: platelet activation
    term:
      id: GO:0030168
      label: platelet activation
- name: Natural Killer Cell Dysfunction
  description: Average NK cytotoxicity is reduced across many studies, but methods and cohorts differ and some large studies are negative. The relationship to infection persistence, individual symptoms and treatment response remains unresolved.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:39483457
    reference_title: Meta-analysis of natural killer cell cytotoxicity in myalgic encephalomyelitis/chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Cytotoxicity in ME/CFS was significantly reduced to about half of healthy control levels, with an overall Hedges' g of 0.96 (0.75-1.18). Heterogeneity was high but was explained by the range of E:T ratios, different methods, and potential outliers.
    explanation: The meta-analysis supports reduced average cytotoxicity, with assay heterogeneity; it is not a universal individual diagnostic marker.
  - reference: PMID:31057538
    reference_title: Cellular Immune Function in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Contrary to previous reports, no significant differences were observed in NK cell numbers, subtype proportions or in vitro responsiveness between ME/CFS patients and healthy control participants.
    explanation: The 251-case biobank study, including 54 severe cases, did not reproduce these NK abnormalities; its assays and sample handling differ from cytotoxicity studies.
  cell_types:
  - preferred_term: natural killer cell
    term:
      id: CL:0000623
      label: natural killer cell
- name: TRPM3-Associated NK-Cell Calcium Dysregulation
  description: Patient NK cells show altered TRPM3 currents and stimulus-dependent calcium responses. Re-addition of extracellular calcium produced higher mitochondrial influx but lower cytosolic influx; pregnenolone-sulfate/TRPM3-dependent responses were reduced in both compartments. Ex vivo naltrexone rescue does not establish clinical benefit or the same defect in muscle or autonomic neurons.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:31736966
    reference_title: Naltrexone Restores Impaired Transient Receptor Potential Melastatin 3 Ion Channel Function in Natural Killer Cells From Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: TRPM3 channel activity was restored in IL-2 stimulated NK cells isolated from ME/CFS patients after incubation for 24 h with NTX.
    explanation: Eight patient and eight control donors; ex vivo rescue does not demonstrate improvement of autonomic symptoms or PEM.
  - reference: PMID:42177403
    reference_title: Deficient TRPM3-linked mitochondrial Ca(2+) influx in natural killer cells associated with myalgic encephalomyelitis/chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Cytosolic Ca2+ influx amplitude and slope were significantly reduced (p < 0.001), with a significantly shorter T1/2 response (p = 0.001) in ME/CFS compared to HC. Ca2+ influx amplitude (p < 0.001) and slope (p < 0.041) into the mitochondria were significantly higher in ME/CFS compared to HC. TRPM3 activation triggered pronounced cytosolic response (P < 0.001) accompanied by mitochondrial Ca2+ increase in HC. TRPM3-dependent cytosolic and mitochondrial Ca2+ mobilisation (P < 0.015) were significantly reduced with a shorter T1/2 response (p < 0.02) in ME/CFS compared to HC.
    explanation: 'Ten cases and ten controls: calcium re-addition produced higher mitochondrial influx despite lower cytosolic response, whereas pregnenolone-sulfate/TRPM3-dependent cytosolic and mitochondrial responses were both reduced. These are stimulus-specific NK-cell assays, not muscle calcium measurements.'
  cell_types:
  - preferred_term: natural killer cell
    term:
      id: CL:0000623
      label: natural killer cell
  biological_processes:
  - preferred_term: calcium ion transmembrane transport
    term:
      id: GO:0070588
      label: calcium ion transmembrane transport
  downstream:
  - target: Natural Killer Cell Dysfunction
    description: Proposed calcium-dependent impairment of NK-cell effector function. The directed hypothesis does not assert reverse causation, uniform NK dysfunction across cohorts or clinical efficacy of naltrexone.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - trpm3_nk_calcium_effector_hypothesis
    evidence:
    - reference: PMID:42177403
      reference_title: Deficient TRPM3-linked mitochondrial Ca(2+) influx in natural killer cells associated with myalgic encephalomyelitis/chronic fatigue syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In NK cells, impaired TRPM3 channel function may lead to dysregulated Ca2+ signalling, subsequently disrupting ATP production, and Ca2+-dependent signalling events, thereby impacting cytotoxic activity and broader immune dysfunction.
      explanation: The study figure describes a conceptual downstream model. Patient-cell calcium responses were measured, but mediation of cytotoxicity or its rescue was not established by this experiment.
- name: Adaptive Immune Memory Dysregulation
  description: Naive and switched-memory B-cell shifts in a selected post-infectious cohort suggest altered immune history. Persistent antigen identity and a causal role in PEM are unproven; negative rituximab results limit simple therapeutic extrapolation.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: DOI:10.1038/s41467-024-45107-3
    reference_title: Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Immune profiling suggested chronic antigenic stimulation with increase in naïve and decrease in switched memory B-cells.
    explanation: Selected deep-phenotyping cohort of 17 post-infectious cases and 21 controls; antigen persistence and causality were inferred, not identified.
  cell_types:
  - preferred_term: naive B cell
    term:
      id: CL:0000788
      label: naive B cell
  - preferred_term: class switched memory B cell
    term:
      id: CL:0000972
      label: class switched memory B cell
- name: T-Cell Immunometabolic Dysfunction
  description: Resting T-cell glycolysis and CD8 mitochondrial membrane potential are reduced in patient-cell assays, with activation-dependent differences. This does not demonstrate a uniform defect in all tissues.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:31830003
    reference_title: Myalgic encephalomyelitis/chronic fatigue syndrome patients exhibit altered T cell metabolism and cytokine associations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Both CD4+ and CD8+ T cells from patients with ME/CFS had reduced glycolysis at rest, whereas CD8+ T cells also had reduced glycolysis following activation.
    explanation: Primary patient-cell metabolism study with 53 cases and 45 controls; this does not establish universal mitochondrial respiratory failure.
  cell_types:
  - preferred_term: CD8-positive, alpha-beta T cell
    term:
      id: CL:0000625
      label: CD8-positive, alpha-beta T cell
  - preferred_term: CD4-positive, alpha-beta T cell
    term:
      id: CL:0000624
      label: CD4-positive, alpha-beta T cell
  biological_processes:
  - preferred_term: glycolytic process
    term:
      id: GO:0006096
      label: glycolytic process
- name: CD8 T-Cell Exhaustion-Associated State
  description: Transcription, chromatin accessibility and surface-marker data support an exhaustion-associated state in selected T-cell subsets. The causal antigen and clinical value of reversing this state remain unknown.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: DOI:10.1073/pnas.2415119121
    reference_title: Transcriptional reprogramming primes CD8+ T cells toward exhaustion in Myalgic encephalomyelitis/chronic fatigue syndrome
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We observed upregulation of key transcription factors associated with T cell exhaustion in CD8+ T cell effector memory subsets, as well as an altered chromatin landscape and metabolic reprogramming consistent with an exhausted immune cell state.
    explanation: Multimodal profiling supports an exhaustion-associated state. The responsible antigen and benefit of checkpoint inhibition remain unproven.
  cell_types:
  - preferred_term: CD8-positive, alpha-beta T cell
    term:
      id: CL:0000625
      label: CD8-positive, alpha-beta T cell
  biological_processes:
  - preferred_term: exhausted T cell differentiation
    term:
      id: GO:0160083
      label: exhausted T cell differentiation
- name: Proposed Delayed Immunometabolic Amplification
  description: The integrated hypothesis proposes that exertion-related metabolic or injury signals produce delayed immune and central symptom amplification. Specific platelet, monocyte and CSF associations exist, but a consistent post-exercise cytokine cascade and peripheral-to-central direction are not established.
  mechanism_confidence: HYPOTHETICAL
  evidence:
  - reference: PMID:38232699
    reference_title: Single-cell transcriptomics of the immune system in ME/CFS at baseline and following symptom provocation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Comparing the transcriptome at baseline and postexercise challenge, we discover patterns indicative of improper platelet activation in patients, with minimal changes elsewhere in the immune system.
    explanation: Exercise-associated platelet signatures do not establish a generalized cytokine cascade or occlusive microthrombosis.
  - reference: PMID:39941050
    reference_title: Exertional Exhaustion (Post-Exertional Malaise, PEM) Evaluated by the Effects of Exercise on Cerebrospinal Fluid Metabolomics-Lipidomics and Serine Pathway in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: two independent cohorts of subjects who had lumbar puncture without exercise (non-exercise group) or after the second of two bouts of submaximal exercise performed on two consecutive days
    explanation: The CSF comparison is between independent cohorts, not paired lumbar punctures or direct muscle-to-CSF tracing.
  - reference: PMID:10226888
    reference_title: Immunological response in chronic fatigue syndrome following a graded exercise test to exhaustion.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: No group differences were seen for any of the immune variables at baseline or after exercise
    explanation: Twenty female cases and fourteen sedentary controls had serial sampling through 24 hours despite increased patient fatigue. This limits a generalized proinflammatory cytokine bridge; it does not exclude every immune mechanism.
  - reference: PMID:24027260
    reference_title: Exercise and sleep deprivation do not change cytokine expression levels in patients with chronic fatigue syndrome.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: We found that these environmental manipulations did not produce clinically significant upregulation of proinflammatory cytokines.
    explanation: Repeated sampling after exercise and sleep deprivation did not support a generalized proinflammatory cytokine response. This limits a generalized proinflammatory cytokine bridge; it does not exclude every immune mechanism.
  - reference: PMID:26148446
    reference_title: 'Chronic fatigue syndrome and circulating cytokines: A systematic review.'
    supports: REFUTE
    evidence_source: OTHER
    snippet: Following physical exercise there were no differences in circulating cytokine levels between cases and controls
    explanation: >-
      A PRISMA systematic review of 38 case-control studies found no
      post-exercise difference in circulating cytokine levels and concluded that
      circulating cytokines do not seem to explain post-exertional fatigue. This
      generalizes the two single negative studies above and is the reason this
      node is framed around platelet and monocyte states rather than a cytokine
      cascade. It constrains a circulating cytokine bridge only: the same review
      found elevated resting TGF-beta in five of eight studies, and tissue-level
      or non-cytokine immune mechanisms are untested by it.
  - reference: PMID:39240417
    reference_title: 'Towards an understanding of physical activity-induced post-exertional malaise: Insights into microvascular alterations and immunometabolic interactions in post-COVID condition and myalgic encephalomyelitis/chronic fatigue syndrome.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: The accumulation of molecules such as lactate, reactive oxygen species or prostaglandins might trigger local and systemic immune activation. Subsequent intensification of bioenergetic inflexibilities, muscular ionic disturbances and modulation of central nervous system functions can lead to an exacerbation of existing pathologies and symptoms.
    explanation: Narrative review explicitly proposes the integrated metabolic/immune/CNS sequence; it is not direct causal validation.
  downstream:
  - target: Post-Exertional Malaise
    description: Hypothesized delayed amplification of symptoms; clinical PEM is established while this molecular sequence remains unproven.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:39240417
      reference_title: 'Towards an understanding of physical activity-induced post-exertional malaise: Insights into microvascular alterations and immunometabolic interactions in post-COVID condition and myalgic encephalomyelitis/chronic fatigue syndrome.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: The accumulation of molecules such as lactate, reactive oxygen species or prostaglandins might trigger local and systemic immune activation. Subsequent intensification of bioenergetic inflexibilities, muscular ionic disturbances and modulation of central nervous system functions can lead to an exacerbation of existing pathologies and symptoms.
      explanation: Narrative review explicitly proposes the integrated metabolic/immune/CNS sequence; it is not direct causal validation.
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
- name: Orthostatic Cerebral Hypoperfusion
  description: Orthostatic challenge produces disproportionate reductions in cerebral flow or flow velocity in specialty cohorts, including some patients with normal heart-rate and blood-pressure responses. Velocity and volumetric flow are different measurements.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:32140630
    reference_title: 'Cerebral blood flow is reduced in ME/CFS during head-up tilt testing even in the absence of hypotension or tachycardia: A quantitative, controlled study using Doppler echography.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: During HUT, extracranial Doppler measurements demonstrate that CBF is reduced in ME/CFS patients with POTS, dOH, and even in those without HR/BP abnormalities.
    explanation: Specialty cohort of 429 cases and 44 controls; normal orthostatic heart rate and blood pressure do not exclude OI. Referral prevalence is not population prevalence.
  - reference: PMID:41576003
    reference_title: Shared autonomic phenotype of long COVID and myalgic encephalomyelitis/chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: reduced orthostatic CBFv (92%/88% in Long COVID/ME/CFS)
    explanation: This retrospective autonomic-referral cohort measures cerebral blood-flow velocity, not volumetric flow; it does not establish a muscle-to-brain causal pathway.
  downstream:
  - target: Orthostatic Intolerance
    description: Reduced upright cerebral perfusion is a plausible contributor to orthostatic symptoms, supported by symptom-flow associations.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32140630
      reference_title: 'Cerebral blood flow is reduced in ME/CFS during head-up tilt testing even in the absence of hypotension or tachycardia: A quantitative, controlled study using Doppler echography.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: During HUT, extracranial Doppler measurements demonstrate that CBF is reduced in ME/CFS patients with POTS, dOH, and even in those without HR/BP abnormalities.
      explanation: Specialty cohort of 429 cases and 44 controls; normal orthostatic heart rate and blood pressure do not exclude OI. Referral prevalence is not population prevalence.
    - reference: PMID:41576003
      reference_title: Shared autonomic phenotype of long COVID and myalgic encephalomyelitis/chronic fatigue syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: reduced orthostatic CBFv (92%/88% in Long COVID/ME/CFS)
      explanation: This retrospective autonomic-referral cohort measures cerebral blood-flow velocity, not volumetric flow; it does not establish a muscle-to-brain causal pathway.
  - target: Cognitive Impairment
    description: Possible contribution during upright stress; brain fog has other potential causes and is not proven to arise solely from perfusion.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32140630
      reference_title: 'Cerebral blood flow is reduced in ME/CFS during head-up tilt testing even in the absence of hypotension or tachycardia: A quantitative, controlled study using Doppler echography.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: During HUT, extracranial Doppler measurements demonstrate that CBF is reduced in ME/CFS patients with POTS, dOH, and even in those without HR/BP abnormalities.
      explanation: Specialty cohort of 429 cases and 44 controls; normal orthostatic heart rate and blood pressure do not exclude OI. Referral prevalence is not population prevalence.
    - reference: PMID:41576003
      reference_title: Shared autonomic phenotype of long COVID and myalgic encephalomyelitis/chronic fatigue syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: reduced orthostatic CBFv (92%/88% in Long COVID/ME/CFS)
      explanation: This retrospective autonomic-referral cohort measures cerebral blood-flow velocity, not volumetric flow; it does not establish a muscle-to-brain causal pathway.
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
- name: Central Motor Activation Abnormality
  description: An older physiological study found impaired voluntary activation during sustained maximal contraction despite normal peripheral metabolism. This is a biological competing or complementary mechanism, not evidence that symptoms are voluntary or psychiatric.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:8423875
    reference_title: Central basis of muscle fatigue in chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The results indicate that patients with CFS have (1) normal fatigability and metabolism at both the intracellular and systemic levels, (2) normal muscle membrane function and excitation-contraction coupling, and (3) an inability to fully activate skeletal muscle during intense, sustained exercise.
    explanation: This older isometric-muscle study supports altered central activation in its cohort, not a psychiatric explanation or a universal exclusion of peripheral pathology.
  downstream:
  - target: Exercise Intolerance
    description: Reduced central drive can contribute to task-specific muscle performance limitations.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:8423875
      reference_title: Central basis of muscle fatigue in chronic fatigue syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The results indicate that patients with CFS have (1) normal fatigability and metabolism at both the intracellular and systemic levels, (2) normal muscle membrane function and excitation-contraction coupling, and (3) an inability to fully activate skeletal muscle during intense, sustained exercise.
      explanation: This older isometric-muscle study supports altered central activation in its cohort, not a psychiatric explanation or a universal exclusion of peripheral pathology.
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
- name: Possible Neuroimmune Activation
  description: Small TSPO PET studies have conflicting findings. TSPO binding is not uniquely microglial activation, and neither generalized neuroinflammation nor a specific link from peripheral muscle signals is established.
  mechanism_confidence: HYPOTHETICAL
  evidence:
  - reference: PMID:24665088
    reference_title: 'Neuroinflammation in Patients with Chronic Fatigue Syndrome/Myalgic Encephalomyelitis: An ¹¹C-(R)-PK11195 PET Study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Nine CFS/ME patients and 10 healthy controls underwent (11)C-(R)-PK11195 PET
    explanation: Small positive TSPO study; ligand binding is an indirect neuroimmune measure and does not uniquely identify activated microglia.
  - reference: PMID:34815320
    reference_title: No Signs of Neuroinflammation in Women With Chronic Fatigue Syndrome or Q Fever Fatigue Syndrome Using the TSPO Ligand [(11)C]-PK11195.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: No statistically significant differences in BPND were found for patients with CFS or patients with QFS compared with HSs.
    explanation: Independent study of nine women with CFS, ten with Q-fever fatigue and nine controls found no group increase; small samples and differing case definitions limit both studies.
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
- name: Autophagy-Associated Macrophage Dysfunction
  description: Atg13 gene depletion in mice disrupts autophagy and mitochondrial metabolism, promotes inflammatory macrophage polarization, and is associated with muscle nerve changes and post-treadmill weakness. This is a mechanistic model, not a validated cause of human ME/CFS or a complete model of delayed human PEM.
  mechanism_confidence: HYPOTHETICAL
  evidence:
  - reference: PMID:41591477
    reference_title: Genetic depletion of the early autophagy protein ATG13 impairs mitochondrial energy metabolism, augments oxidative stress, induces the polarization of macrophages to the M1 inflammatory mode, and compromises myelin integrity in skeletal muscle.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: ablation of the atg13 gene resulted in increased infiltration of M1Mφs into the muscle vasculature, deterioration of myelin integrity in nerve bundles, and a reduction in muscle strength following treadmill exercise.
    explanation: Genetically depleted mouse model supports autophagy-macrophage-muscle coupling; human ME/CFS ATG13 causation is unproven.
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  biological_processes:
  - preferred_term: autophagy
    term:
      id: GO:0006914
      label: autophagy
- name: Gut Microbial Butyrate-Related Dysbiosis
  description: Primary stool metagenomics and metabolomics show reduced butyrate-related capacity and altered microbial composition in some cohorts. Illness duration, diet, IBS and medication can influence results. Causality, epithelial barrier leakage and a gut-to-immune-to-PEM sequence remain unproven.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:36758522
    reference_title: Deficient butyrate-producing capacity in the gut microbiome is associated with bacterial network disturbances and fatigue symptoms in ME/CFS.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Functional metagenomics, qPCR, and metabolomics of fecal short-chain fatty acids confirmed a deficient microbial capacity for butyrate synthesis.
    explanation: Primary multi-omic study of 106 cases and 91 controls; lower butyrate-associated capacity is not proof of intestinal leakage or a cause of PEM.
  - reference: PMID:36758521
    reference_title: Multi-'omics of gut microbiome-host interactions in short- and long-term myalgic encephalomyelitis/chronic fatigue syndrome patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Short-term patients showed significant microbial dysbiosis, while long-term patients had largely resolved microbial dysbiosis but had metabolic and clinical aberrations.
    explanation: Cross-sectional illness-duration cohorts differ; this is not a within-person longitudinal demonstration of microbial recovery.
- name: Proposed Peripheral Vesicle-Microglial Signaling
  description: A 2022 study reports higher vesicle-associated serum mitochondrial DNA after exercise and microglial IL-1beta release after exposure to patient vesicle preparations. This supports a candidate peripheral inflammatory signal in vitro, without establishing which vesicle cargo is causal, a muscle source, blood-brain-barrier transport or an in vivo contribution to PEM. A matched healthy exercise series and independent donor-level bioactivity replication remain important.
  mechanism_confidence: HYPOTHETICAL
  evidence:
  - reference: PMID:36153118
    reference_title: Exosome-associated mitochondrial DNA from patients with myalgic encephalomyelitis/chronic fatigue syndrome stimulates human microglia to release IL-1β.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we show that mitochondrial DNA (mtDNA) associated with serum exosomes, is increased in ME/CFS patients only after exercise.
    explanation: The publication reports paired patient exercise-associated change; an equivalently exercised healthy-control series is not demonstrated.
  - reference: PMID:36153118
    reference_title: Exosome-associated mitochondrial DNA from patients with myalgic encephalomyelitis/chronic fatigue syndrome stimulates human microglia to release IL-1β.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Moreover, exosomes isolated from patients with ME/CFS stimulate significant release of IL-1β from cultured human microglia.
    explanation: Patient serum vesicle preparations have in vitro bioactivity. This does not establish mtDNA necessity, muscle origin, BBB passage or human brain inflammation.
  downstream:
  - target: Possible Neuroimmune Activation
    description: Hypothetical extension of vesicle-preparation bioactivity to neuroimmune activation in patients. This requires biologically effective CNS exposure and in vivo confirmation; neither is demonstrated by the cultured-cell assay.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - exertion_perfusion_muscle_immunometabolic_pem_model
    evidence:
    - reference: PMID:36153118
      reference_title: Exosome-associated mitochondrial DNA from patients with myalgic encephalomyelitis/chronic fatigue syndrome stimulates human microglia to release IL-1β.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Moreover, exosomes isolated from patients with ME/CFS stimulate significant release of IL-1β from cultured human microglia.
      explanation: Cultured microglial IL-1beta release supports the candidate response. Human brain exposure, BBB passage, necessary cargo and in vivo neuroimmune consequences remain unverified; the clinical PET evidence is conflicting.
mechanistic_hypotheses:
- hypothesis_group_id: trpm3_nk_calcium_effector_hypothesis
  hypothesis_label: TRPM3-Dependent NK-Cell Calcium and Effector Function
  status: EMERGING
  description: Altered TRPM3-dependent calcium signaling may impair NK-cell cytotoxic function. Patient-cell current and calcium assays support upstream abnormalities, but downstream mediation, patient-wide generality and symptom benefit from channel rescue remain unresolved.
  evidence:
  - reference: PMID:42177403
    reference_title: Deficient TRPM3-linked mitochondrial Ca(2+) influx in natural killer cells associated with myalgic encephalomyelitis/chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: In NK cells, impaired TRPM3 channel function may lead to dysregulated Ca2+ signalling, subsequently disrupting ATP production, and Ca2+-dependent signalling events, thereby impacting cytotoxic activity and broader immune dysfunction.
    explanation: The study figure describes a conceptual downstream model. Patient-cell calcium responses were measured, but mediation of cytotoxicity or its rescue was not established by this experiment.
- hypothesis_group_id: exertion_perfusion_muscle_immunometabolic_pem_model
  hypothesis_label: Exertion-Perfusion-Muscle Immunometabolic PEM Model
  status: EMERGING
  description: >-
    Exertion may expose neurovascular or muscle metabolic limitations in a subset of patients, followed
    by delayed immune and central amplification of symptoms. Low-flow preload failure, high-flow
    impaired extraction, tissue sodium changes and immune-state abnormalities are distinct observations.
    The ordering and necessity of the proposed links remain unresolved.
  notes: >-
    Retain EMERGING after source-level assessment of OpenScientist. Corrected its false absence of
    sodium MRI and acute hemodynamic intervention evidence, 50% small-fiber-neuropathy figure (31%
    in the cited cohort), review-as-primary EM attribution and cohort conflations. The 2024 EM study
    lacks healthy EM controls; the exercise-biopsy study is in long COVID and does not demonstrate
    intravascular microclots. A 2022 sodium MRI pilot measures mixed tissue sodium, not isolated
    intracellular sodium or calcium overload. Acute pyridostigmine improves exercise hemodynamics
    but does not establish durable PEM benefit. Positive and negative day-two CPET studies coexist.
    None of these findings proves an obligatory muscle-to-immune-to-CNS sequence or validated biological
    subtype boundaries.
  evidence:
  - reference: PMID:33577778
    reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction.
    explanation: 'Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.'
  - reference: PMID:36494667
    reference_title: Muscle sodium content in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Baseline tissue sodium content was higher in all 5 lower leg muscle compartments in ME/CFS compared to controls.
    explanation: Six female cases and six matched controls underwent sodium MRI before and after three minutes of plantar flexion. The acquisition could not isolate intracellular from extracellular sodium.
  - reference: PMID:35526605
    reference_title: 'Neurovascular Dysregulation and Acute Exercise Intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Randomized, Placebo-Controlled Trial of Pyridostigmine.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The peak Vo2 increased after pyridostigmine but decreased after placebo (13.3 ± 13.4 mL/min vs -40.2 ± 21.3 mL/min; P < .05).
    explanation: 'Randomized 45-person acute trial: 60 mg pyridostigmine between two iCPETs separated by 50 minutes improved the relative exercise response. This does not test delayed PEM or durable treatment benefit.'
  - reference: PMID:38338957
    reference_title: Functional and Morphological Differences of Muscle Mitochondria in Chronic Fatigue Syndrome and Post-COVID Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Due to the lack of an EM control group, the mean size and shape of CFS and PCS can only be compared between the respective syndromes.
    explanation: The direct 2024 study compared mitochondrial ultrastructure in 14 CFS and 14 PCS samples without healthy EM controls. OXPHOS used historical healthy controls; between-syndrome morphology does not prove calcium-mediated injury.
  - reference: PMID:9527150
    reference_title: Muscle fibre characteristics and lactate responses to exercise in chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: No significant ultrastructural abnormalities were found.
    explanation: An older 105-case biopsy study examined 41 samples by EM; findings qualify a universal structural mitochondrial lesion.
  - reference: PMID:38965566
    reference_title: 'Cardiopulmonary and metabolic responses during a 2-day CPET in myalgic encephalomyelitis/chronic fatigue syndrome: translating reduced oxygen consumption to impairment status to treatment considerations.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Abnormal post-exertional CPET responses persisted compared to CTL matched for aerobic capacity, indicating that fitness level does not predispose to exertion intolerance in ME/CFS.
    explanation: 'Canadian-criteria study: 84 cases and 71 sedentary controls, with 55 matched pairs; supports impaired recovery in this cohort.'
  - reference: PMID:42212259
    reference_title: Cardiopulmonary exercise test results do not change over two sequential days in patients with chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The data do not support using the 2-day CPET protocol to define PEM or disability.
    explanation: The 58-case and 25-control study required PEM and found no day-two VO2 decline. Absence of this physiological pattern does not exclude symptom-defined PEM or disability.
  - reference: PMID:10226888
    reference_title: Immunological response in chronic fatigue syndrome following a graded exercise test to exhaustion.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: No group differences were seen for any of the immune variables at baseline or after exercise
    explanation: Twenty female cases and fourteen sedentary controls had serial sampling through 24 hours despite increased patient fatigue.
  - reference: PMID:24027260
    reference_title: Exercise and sleep deprivation do not change cytokine expression levels in patients with chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We found that these environmental manipulations did not produce clinically significant upregulation of proinflammatory cytokines.
    explanation: Repeated sampling after exercise and sleep deprivation did not support a generalized proinflammatory cytokine response.
phenotypes:
- name: Post-Exertional Malaise
  category: Multisystem
  description: Disproportionate worsening after physical, cognitive, emotional or social activity, often delayed by hours or days and with prolonged recovery. Clinical PEM is not defined by a mandatory day-two VO2 fall.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: has a prolonged recovery time that may last hours, days, weeks or longer.
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
  phenotype_term:
    preferred_term: Postexertional symptom exacerbation
    term:
      id: HP:0030973
      label: Postexertional symptom exacerbation
  frequency: OBLIGATE
- name: Fatigue
  category: Multisystem
  description: New or substantially worsened disabling fatigue with loss of previous function, worsened by activity and not significantly relieved by rest.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: and is not significantly relieved by rest.
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
  phenotype_term:
    preferred_term: Fatigue
    term:
      id: HP:0012378
      label: Fatigue
  frequency: OBLIGATE
- name: Cognitive Impairment
  category: Multisystem
  description: Problems with concentration, working memory, word finding and processing, often worsened by activity or upright posture. NAM criteria allow cognition or OI; NICE requires cognitive difficulties.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: short-term memory problems, and difficulty concentrating or multitasking.
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
  phenotype_term:
    preferred_term: Cognitive impairment
    term:
      id: HP:0100543
      label: Cognitive impairment
- name: Orthostatic Intolerance
  category: Multisystem
  description: Symptoms worsen while sitting or standing and improve with recumbency. POTS, delayed hypotension and normal heart-rate/blood-pressure patterns can all occur. No exact HPO term was found; orthostatic hypotension is not an equivalent binding.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: including dizziness, palpitations, fainting, nausea on standing or sitting upright from a reclining position
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
- name: Unrefreshing Sleep
  category: Multisystem
  description: Sleep fails to restore prior function; fragmented sleep, altered timing and hypersomnia may coexist.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: feeling exhausted, feeling flu-like and stiff on waking
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
  phenotype_term:
    preferred_term: Non-restorative sleep
    term:
      id: HP:5200292
      label: Non-restorative sleep
- name: Myalgia
  category: Multisystem
  description: Muscle pain can be persistent or worsened by exertion.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: myalgia, headaches, eye pain, abdominal pain or joint pain
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
  phenotype_term:
    preferred_term: Myalgia
    term:
      id: HP:0003326
      label: Myalgia
- name: Headache
  category: Multisystem
  description: Headaches may accompany the illness and can worsen after exertion; assess new or changing patterns separately.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: myalgia, headaches, eye pain, abdominal pain or joint pain
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
  phenotype_term:
    preferred_term: Headache
    term:
      id: HP:0002315
      label: Headache
- name: Photophobia
  category: Multisystem
  description: Light sensitivity can become severe and limit clinical assessment or ordinary daily activities.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: hypersensitivity to light, sound, touch, movement, temperature extremes and smells
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
  phenotype_term:
    preferred_term: Photophobia
    term:
      id: HP:0000613
      label: Photophobia
- name: Sound Sensitivity
  category: Multisystem
  description: Intolerance of sound can be severe, particularly with more disabling illness. The HPO phonophobia binding captures this sound-intolerance feature rather than establishing an audiometric hyperacusis diagnosis.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: hypersensitivity to light, sound, touch, movement, temperature extremes and smells
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
  phenotype_term:
    preferred_term: Phonophobia
    term:
      id: HP:0002183
      label: Phonophobia
- name: Gastrointestinal Symptoms
  category: Multisystem
  description: Nausea, abdominal pain, constipation and bloating occur; irritable bowel syndrome can coexist. A composite symptom group is retained rather than one misleading ontology binding.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: gastrointestinal difficulties such as nausea, incontinence, constipation and bloating
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
- name: Flu-Like Symptoms
  category: Multisystem
  description: Sore throat, tender glands, chills and malaise may occur or recur. These symptoms do not demonstrate recurrent pathogen-proven infection or an immunodeficiency.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: flu-like symptoms, including sore throat, tender glands, nausea, chills or muscle aches
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
- name: Dysphagia
  category: Multisystem
  description: Some people with very severe illness have difficulty chewing or swallowing and require specialist nutritional support. This is not a universal manifestation.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: reduced ability or inability to speak or swallow
    explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
  phenotype_term:
    preferred_term: Dysphagia
    term:
      id: HP:0002015
      label: Dysphagia
- name: Exercise Intolerance
  category: Musculoskeletal
  description: Reduced tolerance of exertion can reflect different neurovascular, metabolic or central physiological patterns. It is distinct from delayed multisystem PEM.
  phenotype_term:
    preferred_term: Exercise intolerance
    term:
      id: HP:0003546
      label: Exercise intolerance
  evidence:
  - reference: PMID:33577778
    reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction.
    explanation: 'Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.'
  - reference: PMID:8423875
    reference_title: Central basis of muscle fatigue in chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The results indicate that patients with CFS have (1) normal fatigability and metabolism at both the intracellular and systemic levels, (2) normal muscle membrane function and excitation-contraction coupling, and (3) an inability to fully activate skeletal muscle during intense, sustained exercise.
    explanation: This older isometric-muscle study supports altered central activation in its cohort, not a psychiatric explanation or a universal exclusion of peripheral pathology.
  - reference: PMID:38965566
    reference_title: 'Cardiopulmonary and metabolic responses during a 2-day CPET in myalgic encephalomyelitis/chronic fatigue syndrome: translating reduced oxygen consumption to impairment status to treatment considerations.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Abnormal post-exertional CPET responses persisted compared to CTL matched for aerobic capacity, indicating that fitness level does not predispose to exertion intolerance in ME/CFS.
    explanation: 'Canadian-criteria study: 84 cases and 71 sedentary controls, with 55 matched pairs; supports impaired recovery in this cohort.'
  - reference: PMID:42212259
    reference_title: Cardiopulmonary exercise test results do not change over two sequential days in patients with chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The data do not support using the 2-day CPET protocol to define PEM or disability.
    explanation: The 58-case and 25-control study required PEM and found no day-two VO2 decline. Absence of this physiological pattern does not exclude symptom-defined PEM or disability.
biochemical:
- name: Natural Killer Cell Cytotoxicity
  presence: Variable
  context: Candidate research phenotype; reduced on average in meta-analysis, not universal or diagnostically validated.
  evidence:
  - reference: PMID:39483457
    reference_title: Meta-analysis of natural killer cell cytotoxicity in myalgic encephalomyelitis/chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Cytotoxicity in ME/CFS was significantly reduced to about half of healthy control levels, with an overall Hedges' g of 0.96 (0.75-1.18). Heterogeneity was high but was explained by the range of E:T ratios, different methods, and potential outliers.
    explanation: The meta-analysis supports reduced average cytotoxicity, with assay heterogeneity; it is not a universal individual diagnostic marker.
  - reference: PMID:31057538
    reference_title: Cellular Immune Function in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Contrary to previous reports, no significant differences were observed in NK cell numbers, subtype proportions or in vitro responsiveness between ME/CFS patients and healthy control participants.
    explanation: The 251-case biobank study, including 54 severe cases, did not reproduce these NK abnormalities; its assays and sample handling differ from cytotoxicity studies.
- name: Cytokine Profiles
  presence: Variable
  context: Case definition, sex, illness duration, severity, assays and timing influence results. Cross-sectional severity associations do not establish an early-disease or post-exercise cytokine surge.
  evidence:
  - reference: PMID:10226888
    reference_title: Immunological response in chronic fatigue syndrome following a graded exercise test to exhaustion.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: No group differences were seen for any of the immune variables at baseline or after exercise
    explanation: Twenty female cases and fourteen sedentary controls had serial sampling through 24 hours despite increased patient fatigue.
  - reference: PMID:24027260
    reference_title: Exercise and sleep deprivation do not change cytokine expression levels in patients with chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We found that these environmental manipulations did not produce clinically significant upregulation of proinflammatory cytokines.
    explanation: Repeated sampling after exercise and sleep deprivation did not support a generalized proinflammatory cytokine response.
- name: Plasma and Urine Metabolomic Profiles
  presence: Variable
  context: Purine, lipid and other concentration differences are research findings. Neither a uniform hypermetabolic nor hypometabolic state, diagnostic classifier or proven muscle-source signal is established.
  evidence:
  - reference: PMID:31277442
    reference_title: Post-Exertional Malaise Is Associated with Hypermetabolism, Hypoacetylation and Purine Metabolism Deregulation in ME/CFS Cases.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The principal biochemical change related to the 7-day severity of PEM was the fall in the purine metabolite, hypoxanthine.
    explanation: Forty-seven cases reported recent PEM severity; a seven-day symptom window is not a serial provoked exercise experiment or a direct measurement of metabolic flux.
  - reference: PMID:27573827
    reference_title: Metabolic features of chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Eighty percent of the diagnostic metabolites were decreased, consistent with a hypometabolic syndrome.
    explanation: The study had 45 cases and 39 controls, 84 total. Concentration profiles and internal classification do not establish organism-wide metabolic shutdown or a validated diagnostic test.
- name: Muscle Tissue Sodium
  presence: Elevated in a small pilot cohort
  context: Research 23Na-MRI finding in six female cases; compartment mixing prevents equating it with intracellular sodium or calcium overload.
  evidence:
  - reference: PMID:36494667
    reference_title: Muscle sodium content in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Baseline tissue sodium content was higher in all 5 lower leg muscle compartments in ME/CFS compared to controls.
    explanation: Six female cases and six matched controls underwent sodium MRI before and after three minutes of plantar flexion. The acquisition could not isolate intracellular from extracellular sodium.
genetic:
- name: HLA-C
  gene_term:
    preferred_term: HLA-C
    term:
      id: hgnc:4933
      label: HLA-C
  association: Population susceptibility association, not Mendelian causation
  notes: HLA-C*07:04 tagged an association in 426 Norwegian cases versus 4511 controls (OR 2.1); linkage disequilibrium prevents assigning causality to the tag allele. Not a diagnostic test.
  evidence:
  - reference: PMID:32210306
    reference_title: Human Leukocyte Antigen alleles associated with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: HLA-C*07:04 (OR 2.1 [95% CI 1.4-3.1])
    explanation: Primary high-resolution HLA association study; one ancestry cohort.
- name: HLA-DQB1
  gene_term:
    preferred_term: HLA-DQB1
    term:
      id: hgnc:4944
      label: HLA-DQB1
  association: Population susceptibility association, not Mendelian causation
  notes: HLA-DQB1*03:03 tagged a second independent association (OR 1.5). HLA associations alone do not prove autoimmunity, a particular antigen or an individual diagnosis.
  evidence:
  - reference: PMID:32210306
    reference_title: Human Leukocyte Antigen alleles associated with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: HLA-DQB1*03:03 (OR 1.5 [95% CI 1.1-2.0])
    explanation: Primary susceptibility association distinct from the prior nonspecific HLA-DRB1 attribution.
environmental:
- name: Preceding Infection
  description: ME/CFS can follow viral or nonviral infection, although onset is not always linked to an identified infection. The Dubbo prospective cohort found persistent CFS in 28 of 253 participants after EBV, Ross River virus or Coxiella burnetii infection. SARS-CoV-2 can also precede a phenotype meeting ME/CFS criteria; long COVID and ME/CFS are overlapping, not identical populations.
  evidence:
  - reference: PMID:16950834
    reference_title: 'Post-infective and chronic fatigue syndromes precipitated by viral and non-viral pathogens: prospective cohort study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: of whom 28 (11%) met the diagnostic criteria for chronic fatigue syndrome. This post-infective fatigue syndrome phenotype was stereotyped and occurred at a similar incidence after each infection.
    explanation: Prospective post-infectious cohort includes a bacterial trigger; it does not estimate the proportion of all ME/CFS with infectious onset.
- name: Exertion Beyond Individual Tolerance
  description: Physical, cognitive, emotional and social demands can trigger or worsen PEM. Upright posture, sensory stimulation and ordinary personal care may be substantial exertion in severe disease.
  effect: Symptom exacerbation
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: (cognitive, physical, emotional and social)
    explanation: Energy management includes nonphysical activity as well as exercise.
  influences_mechanisms:
  - target: Post-Exertional Malaise
    environmental_effect: EXACERBATES
    description: Activity beyond fluctuating individual limits can provoke symptom exacerbation.
    evidence:
    - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
      reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: has a prolonged recovery time that may last hours, days, weeks or longer.
      explanation: NICE clinical guidance describes this manifestation; frequency varies by case definition and severity.
treatments:
- name: Individualized Energy Management
  description: Collaborative pacing across physical, cognitive, emotional and social demands aims to reduce PEM and stabilize activity within fluctuating limits. Include planned rest and flexible adjustment; it is not a cure or a fixed upward exercise prescription. NICE advises against fixed incremental graded exercise programs.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: uses a flexible, tailored approach so that activity is never automatically increased
    explanation: NICE emphasizes individualized adjustment, not automatic progression.
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'Do not offer people with ME/CFS:'
    explanation: Negative lead-in to NICE recommendation 1.11.14, including the fixed-increment exercise item quoted below.
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: that uses fixed incremental increases in physical activity or exercise
    explanation: NICE recommendation 1.11.14 says not to offer this approach.
  target_mechanisms:
  - target: Post-Exertional Malaise
    treatment_effect: MODULATES
    description: Symptom-guided reduction of exertion beyond individual tolerance; supportive care rather than correction of a proven molecular lesion.
    evidence:
    - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
      reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: uses a flexible, tailored approach so that activity is never automatically increased
      explanation: NICE emphasizes individualized adjustment, not automatic progression.
- name: Sleep and Pain Management
  description: Address sleep patterns and coexisting sleep disorders, and investigate and treat pain using individualized usual clinical care. Medication review is important because people with ME/CFS may be more intolerant of medicines; start lower and titrate when appropriate.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Investigate and manage the person's pain according to best practice
    explanation: NICE recommends symptom-focused pain care.
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: may be more intolerant of drug treatment
    explanation: NICE recommends considering lower starting doses and gradual increases.
- name: Orthostatic Intolerance Management
  description: Tailor nonpharmacological and, when needed, pharmacological management to the documented autonomic pattern and comorbidities. Specialist oversight is appropriate for medication and severe or worsening symptoms. An indiscriminate vasodilator is not justified by the perfusion hypothesis because low preload and high-flow impaired extraction are distinct patterns.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: should only be prescribed or overseen by a healthcare professional with expertise in orthostatic intolerance.
    explanation: NICE specifies expertise for OI medication.
  - reference: PMID:33577778
    reference_title: Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: These results identify two types of peripheral neurovascular dysregulation that are biologically plausible contributors to ME/CFS exertional intolerance-depressed Qc from impaired venous return, and impaired peripheral oxygen extraction.
    explanation: 'Selected low-right-atrial-pressure cohort: low-flow impaired venous return and high-flow impaired extraction are separate physiological patterns, not one universal lesion.'
- name: Severe-Disease Support and Nutrition
  description: Offer accessible or home-based care, sensory accommodation, mobility aids, communication support, assistance with daily activities and nutrition/hydration assessment. Evaluate swallowing problems and malnutrition; oral support or enteral feeding may be required. Assess skin and immobility-related complications individually.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: are unable to eat and digest food easily and may need support with hydration and nutrition
    explanation: NICE describes practical needs in severe and very severe illness.
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: oral nutrition support and enteral feeding
    explanation: NICE includes enteral support when clinically indicated.
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: areas at risk of pressure ulcers
    explanation: NICE includes skin and mobility complications in physical-function management.
- name: Supportive Psychological and Social Care
  description: Offer practical support for education, work, benefits and carers. CBT is optional support for symptom management, function and distress when the person wants it; it is not curative and does not assume abnormal illness beliefs cause ME/CFS.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: does not assume people have 'abnormal' illness beliefs and behaviours
    explanation: NICE distinguishes supportive CBT from an etiologic or curative claim.
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: where to access advice about financial support
    explanation: NICE includes practical social support.
- name: Pyridostigmine
  description: Investigational for ME/CFS exertional intolerance. A 45-person randomized trial found an acute relative improvement of peak VO2, cardiac output and filling pressure after one 60-mg dose, with repeat iCPET after 50 minutes. This does not establish sustained symptom or PEM benefit; the ongoing LIFT trial tests longer-term treatment.
  evidence:
  - reference: PMID:35526605
    reference_title: 'Neurovascular Dysregulation and Acute Exercise Intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Randomized, Placebo-Controlled Trial of Pyridostigmine.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The peak Vo2 increased after pyridostigmine but decreased after placebo (13.3 ± 13.4 mL/min vs -40.2 ± 21.3 mL/min; P < .05).
    explanation: 'Randomized 45-person acute trial: 60 mg pyridostigmine between two iCPETs separated by 50 minutes improved the relative exercise response. This does not test delayed PEM or durable treatment benefit.'
  target_mechanisms:
  - target: Reduced Exercise Cardiac Output
    treatment_effect: MODULATES
    description: Acute relative preservation of exercise cardiac output and increased filling pressure in the randomized iCPET experiment; durable symptom benefit remains unproven.
    evidence:
    - reference: PMID:35526605
      reference_title: 'Neurovascular Dysregulation and Acute Exercise Intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Randomized, Placebo-Controlled Trial of Pyridostigmine.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The peak Vo2 increased after pyridostigmine but decreased after placebo (13.3 ± 13.4 mL/min vs -40.2 ± 21.3 mL/min; P < .05).
      explanation: 'Randomized 45-person acute trial: 60 mg pyridostigmine between two iCPETs separated by 50 minutes improved the relative exercise response. This does not test delayed PEM or durable treatment benefit.'
  - target: Impaired Venous Return
    treatment_effect: MODULATES
    description: Acute increase in filling pressure in the randomized iCPET study; this is not evidence of durable normalization of venous tone.
    evidence:
    - reference: PMID:35526605
      reference_title: 'Neurovascular Dysregulation and Acute Exercise Intolerance in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Randomized, Placebo-Controlled Trial of Pyridostigmine.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Pyridostigmine improves peak Vo2 in ME/CFS by increasing cardiac output and right ventricular filling pressures.
      explanation: Acute physiological interpretation of the 45-person randomized trial; no long-term PEM outcome was tested.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: Pyridostigmine
      term:
        id: NCIT:C47697
        label: Pyridostigmine Bromide
- name: Low-Dose Naltrexone
  description: Investigational/off-label for ME/CFS. Ex vivo restoration of NK-cell TRPM3 activity is a mechanistic lead, not proof of clinical efficacy. LIFT studies pyridostigmine and low-dose naltrexone; a separate dose-finding trial is registered without posted outcomes as of September 2026.
  evidence:
  - reference: PMID:31736966
    reference_title: Naltrexone Restores Impaired Transient Receptor Potential Melastatin 3 Ion Channel Function in Natural Killer Cells From Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: TRPM3 channel activity was restored in IL-2 stimulated NK cells isolated from ME/CFS patients after incubation for 24 h with NTX.
    explanation: Eight patient and eight control donors; ex vivo rescue does not demonstrate improvement of autonomic symptoms or PEM.
  target_mechanisms:
  - target: TRPM3-Associated NK-Cell Calcium Dysregulation
    treatment_effect: MODULATES
    description: Ex vivo NK-cell target modulation; not a demonstrated clinical effect of oral low-dose treatment.
    evidence:
    - reference: PMID:31736966
      reference_title: Naltrexone Restores Impaired Transient Receptor Potential Melastatin 3 Ion Channel Function in Natural Killer Cells From Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: TRPM3 channel activity was restored in IL-2 stimulated NK cells isolated from ME/CFS patients after incubation for 24 h with NTX.
      explanation: Eight patient and eight control donors; ex vivo rescue does not demonstrate improvement of autonomic symptoms or PEM.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: Naltrexone
      term:
        id: NCIT:C62055
        label: Naltrexone
- name: Rituximab
  description: 'Not supported as routine ME/CFS treatment: the 151-person phase III trial found no clinical benefit over placebo. B-cell associations or an autoimmune hypothesis do not override this negative intervention result.'
  evidence:
  - reference: PMID:30934066
    reference_title: 'B-Lymphocyte Depletion in Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Randomized, Double-Blind, Placebo-Controlled Trial.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: B-cell depletion using several infusions of rituximab over 12 months was not associated with clinical improvement in patients with ME/CFS.
    explanation: Multicenter 151-person placebo-controlled trial did not support rituximab efficacy.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: Rituximab
      term:
        id: NCIT:C1702
        label: Rituximab
- name: Cyclophosphamide
  description: An uncontrolled 40-person study and six-year follow-up reported improvement in some participants. Lack of a randomized comparator and toxicity preclude routine use; the authors recommend restriction to clinical trials.
  evidence:
  - reference: PMID:39042627
    reference_title: Six-year follow-up of participants in two clinical trials of rituximab or cyclophosphamide in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: cyclophosphamide carries toxicity concerns and should not be used for ME/CFS patients outside clinical trials.
    explanation: The six-year follow-up does not turn the original open-label study into a controlled efficacy result.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: Cyclophosphamide
      term:
        id: NCIT:C405
        label: Cyclophosphamide
- name: Plasma Exchange
  description: 'Investigational: a single patient with pre-existing ME/CFS and worsening after SARS-CoV-2 infection improved following plasma exchange amid other treatment changes. This cannot establish efficacy, identify pathogenic antibodies or support routine use. Uncontrolled immunoadsorption studies likewise require randomized confirmation.'
  evidence:
  - reference: PMID:42158223
    reference_title: 'Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Successful Therapeutic Plasma Exchange Treatment After SARS-CoV-2 Infection-A Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Our successful case highlights the need to investigate novel therapeutic approaches, including plasma exchange.
    explanation: A single uncontrolled case is hypothesis-generating; receptor antibody levels did not establish a diagnostic test or causal mechanism.
  treatment_term:
    preferred_term: Plasmapheresis
    term:
      id: NCIT:C15304
      label: Plasmapheresis
discussions:
- discussion_id: gap_mecfs_pem_causal_ordering
  prompt: >
    Which causal edge best connects exertion to delayed multi-system symptom
    worsening in ME/CFS: impaired microvascular oxygen delivery/extraction,
    skeletal muscle ionic and mitochondrial disturbance, immune-metabolic
    signaling, autonomic dysfunction, central nervous system amplification, or a
    subtype-specific combination?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Impaired Peripheral Oxygen Extraction
  - pathophysiology#Skeletal Muscle Bioenergetic Disturbance
  - pathophysiology#Proposed Delayed Immunometabolic Amplification
  - phenotypes#Post-Exertional Malaise
  rationale: >-
    No study in the reviewed literature measures and perturbs the complete peripheral-perfusion,
    myocyte-ion, metabolic, immune and CNS sequence in the same ME/CFS participants. Existing sodium
    MRI, acute pyridostigmine, single-cell exercise and long-COVID muscle-biopsy studies narrow the
    gaps; they do not validate the entire chain. Muscle sodium compartment specificity, causal ordering,
    subgroup boundaries and physiological/symptom discordance remain open. A 2022 patient serum-vesicle/microglial
    assay demonstrates peripheral-preparation bioactivity but not muscle source, mtDNA-specific causality,
    BBB transport or in vivo brain effects.
  proposed_experiments:
  - experiment_id: exp_mecfs_pem_serial_exertion_perfusion_multiomics
    name: Serial exertion-challenge perfusion and muscle multi-omics cohort
    description: >-
      Use a prospectively registered, severity-adapted cohort with activity-matched controls and
      carefully tolerated provocation. Measure symptoms and selected perfusion, muscle metabolism,
      sodium-compartment, immune and autonomic endpoints across baseline, immediate, 24–72-hour and
      recovery windows. An invasive or maximal exercise battery should not be imposed on people unable
      to tolerate it. Specify missing-data handling, medication/activity covariates and independent
      validation before subgroup discovery.
    experiment_type:
      preferred_term: longitudinal exertion-challenge cohort
    model_systems:
    - name: Human ME/CFS exertion-challenge cohort
      description: >
        Patient cohort designed to temporally order peripheral perfusion,
        skeletal muscle, metabolic, immune, autonomic, and symptom readouts
        during PEM induction and recovery.
      experimental_model_type: OTHER
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
    decision_criterion: >-
      Temporal precedence and adjusted mediation would increase plausibility but would not establish
      causality because unmeasured confounding and feedback remain possible. A targeted randomized
      perturbation must demonstrate target engagement and downstream physiological and symptom changes,
      with rescue and safety outcomes, to test direction. Compartment-specific sodium results are
      needed before inferring intracellular calcium loading.
    would_support:
    - pathophysiology#Impaired Peripheral Oxygen Extraction
    - pathophysiology#Skeletal Muscle Bioenergetic Disturbance
    - pathophysiology#Proposed Delayed Immunometabolic Amplification
    would_refute:
    - mechanistic_hypotheses#exertion_perfusion_muscle_immunometabolic_pem_model
  evidence:
  - reference: PMID:36153118
    reference_title: Exosome-associated mitochondrial DNA from patients with myalgic encephalomyelitis/chronic fatigue syndrome stimulates human microglia to release IL-1β.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we show that mitochondrial DNA (mtDNA) associated with serum exosomes, is increased in ME/CFS patients only after exercise.
    explanation: The publication reports paired patient exercise-associated change; an equivalently exercised healthy-control series is not demonstrated.
  - reference: PMID:36153118
    reference_title: Exosome-associated mitochondrial DNA from patients with myalgic encephalomyelitis/chronic fatigue syndrome stimulates human microglia to release IL-1β.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Moreover, exosomes isolated from patients with ME/CFS stimulate significant release of IL-1β from cultured human microglia.
    explanation: Patient serum vesicle preparations have in vitro bioactivity. This does not establish mtDNA necessity, muscle origin, BBB passage or human brain inflammation.
- discussion_id: gap_mecfs_genetic_architecture
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: Which ME/CFS susceptibility variants act through which tissues and effector genes?
  rationale: The 2025 DecodeME preprint reports eight associated loci in up to 15,579 cases and 259,909 ancestry-matched controls. It is not peer reviewed, and nearby genes are not proven effector genes. HLA and GWAS findings support polygenic susceptibility without establishing Mendelian inheritance, a clinical test or this specific perfusion-to-PEM pathway.
  evidence:
  - reference: DOI:10.1101/2025.08.06.25333109
    reference_title: Initial findings from the DecodeME genome-wide association study of myalgic encephalomyelitis/chronic fatigue syndrome
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We recruited 21,620 ME/CFS cases and performed genome-wide association studies (GWAS) for up to 15,579 cases and 259,909 population controls with European genetic ancestry.
    explanation: DecodeME is a preprint; locus associations do not identify causal effector genes.
- discussion_id: gap_mecfs_upstream_alternatives
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: Do receptor autoantibodies, microbial metabolites or central regulatory abnormalities initiate or maintain the observed neurovascular and immune states?
  rationale: These hypotheses may complement rather than exclude the perfusion model. Receptor-antibody concentration associations do not establish receptor agonism or causality; microbial metabolite associations do not prove barrier leakage. An older central activation study provides an alternative physiological direction. Negative rituximab evidence and extracellular rather than intravascular muscle amyloid deposits constrain overly simple autoimmune and microclot models.
  evidence:
  - reference: PMID:33889154
    reference_title: Delineating the Association Between Soluble CD26 and Autoantibodies Against G-Protein Coupled Receptors, Immunological and Cardiovascular Parameters Identifies Distinct Patterns in Post-Infectious vs. Non-Infection-Triggered Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: could not confirm diagnostic suitability
    explanation: sCD26 and autoantibody correlations were subgroup dependent and did not establish a diagnostic assay or receptor dysfunction.
  - reference: PMID:8423875
    reference_title: Central basis of muscle fatigue in chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The results indicate that patients with CFS have (1) normal fatigability and metabolism at both the intracellular and systemic levels, (2) normal muscle membrane function and excitation-contraction coupling, and (3) an inability to fully activate skeletal muscle during intense, sustained exercise.
    explanation: This older isometric-muscle study supports altered central activation in its cohort, not a psychiatric explanation or a universal exclusion of peripheral pathology.
  - reference: PMID:38177128
    reference_title: Muscle abnormalities worsen after post-exertional malaise in long COVID.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We conclude that amyloid-containing deposits are not present within capillaries.
    explanation: The 25-person long-COVID PEM cohort and 21 recovered controls had paired biopsies. Deposits were extravascular; this contradicts equating the observation with occlusive muscle microclots.
  - reference: PMID:36758522
    reference_title: Deficient butyrate-producing capacity in the gut microbiome is associated with bacterial network disturbances and fatigue symptoms in ME/CFS.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Functional metagenomics, qPCR, and metabolomics of fecal short-chain fatty acids confirmed a deficient microbial capacity for butyrate synthesis.
    explanation: Primary multi-omic study of 106 cases and 91 controls; lower butyrate-associated capacity is not proof of intestinal leakage or a cause of PEM.
  - reference: PMID:36758521
    reference_title: Multi-'omics of gut microbiome-host interactions in short- and long-term myalgic encephalomyelitis/chronic fatigue syndrome patients.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Short-term patients showed significant microbial dysbiosis, while long-term patients had largely resolved microbial dysbiosis but had metabolic and clinical aberrations.
    explanation: Cross-sectional illness-duration cohorts differ; this is not a within-person longitudinal demonstration of microbial recovery.
notes: 'Clinical diagnosis and supportive management are established; disease-wide causal mechanisms and biomarkers remain under investigation. Severity grades are not validated molecular subtypes. No disease-specific GeneReviews chapter was identified; clinical coverage was checked against NICE NG206 and CDC diagnostic guidance. The OpenScientist assessment distinguishes retained findings, methodological limitations, missed pre-report studies and later evidence. Literature and registry review date: 2026-09-04. Graph links distinguish observations from explicitly proposed transitions. The erythrocyte assay authors propose pain and fatigue through impaired perfusion/oxygenation; an edge to measured systemic oxygen extraction is omitted because delivery and extraction are different quantities. Unrefreshing sleep and headache remain clinically documented without assigning an unverified unique upstream mechanism.'
references:
- reference: DOI:10.1126/science.abo1261
  title: Understanding myalgic encephalomyelitis
  found_in:
  - Myalgic_Encephalomyelitis_Chronic_Fatigue_Syndrome-deep-research-perplexity.md
  findings: []
- reference: DOI:10.3389/fimmu.2024.1386607
  title: 'Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: the biology of a neglected disease'
  found_in:
  - Myalgic_Encephalomyelitis_Chronic_Fatigue_Syndrome-deep-research-falcon.md
  - Myalgic_Encephalomyelitis_Chronic_Fatigue_Syndrome-deep-research-perplexity.md
  findings: []
- reference: DOI:10.3389/fneur.2022.877772
  title: Molecular Mechanisms of Neuroinflammation in ME/CFS and Long COVID to Sustain Disease and Promote Relapses
  found_in:
  - Myalgic_Encephalomyelitis_Chronic_Fatigue_Syndrome-deep-research-perplexity.md
  findings: []
- reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
  title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
  findings: []
- reference: url:https://www.cdc.gov/me-cfs/hcp/diagnosis/index.html
  title: Diagnosing ME/CFS | ME/CFS | CDC
  findings: []
datasets:
- accession: geo:GSE293840
  title: Circulating cell-free RNA signatures for the characterization and diagnosis of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)
  description: People living with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) experience heterogeneous and debilitating symptoms that lack sufficient biological explanation, compounded by the absence of accurate, noninvasive diagnostic tools. To address these challenges, we explored circulating cell-free RNA (cfRNA) as a blood-borne bioanalyte to monitor ME/CFS. cfRNA is released into the bloodstream during cellular turnover and reflects dynamic changes in gene expression, cellular signaling, and tissue-specific processes.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_count: 168
  publication: PMID:40789036
  notes: Identified by GEO DataSets index search for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-07-31. Title, sample count, and organism are GEO's own values. Accession reverified on 2026-09-04. Dataset records or repeated samples are not necessarily independent participants. Provider-report citation does not establish that OpenScientist downloaded or analyzed this dataset.
- accession: geo:GSE227375
  title: Sex-Dependent Transcriptional Changes in response to stress in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome
  description: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex, multi-symptom illness characterized by debilitating fatigue and post-exertional malaise (PEM). Numerous studies have reported sex differences at the epidemiological, cellular, and molecular levels between male and female ME/CFS patients. To gain further insight into these sex-dependent changes, we evaluated differential gene expression by RNA-sequencing in 35 ME/CFS patients (24 female, 11 male) and 34 matched healthy control participants (21 female and 13 male) during and after an exercise challenge intended to provoke PEM.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_count: 187
  publication: PMID:37373402
  notes: Identified by GEO DataSets index search for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-07-31. Title, sample count, and organism are GEO's own values. Accession reverified on 2026-09-04. Dataset records or repeated samples are not necessarily independent participants. Provider-report citation does not establish that OpenScientist downloaded or analyzed this dataset.
- accession: geo:GSE156792
  title: Genome-epigenome interactions associated with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome
  description: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex disease of unknown etiology. Multiple studies point to disruptions in immune functioning in ME/CFS patients as well as specific genetic polymorphisms and alterations of the DNA methylome in lymphocytes. However, potential interactions between DNA methylation and genetic background in relation to ME/CFS have not been examined. In this study we explored this association by characterizing the epigenetic (~480 thousand CpG loci) and genetic (~4.3 million SNPs) variation between cohorts of ME/CFS patients and healthy controls.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: METHYLATION
  sample_count: 109
  publication: PMID:30516085
  notes: Identified by GEO DataSets index search for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-07-31. Title, sample count, and organism are GEO's own values. Accession reverified on 2026-09-04. Dataset records or repeated samples are not necessarily independent participants. Provider-report citation does not establish that OpenScientist downloaded or analyzed this dataset.
- accession: metabolomics_workbench:ST000800
  title: Insights into myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) phenotypes through comprehensive metabolomics
  notes: Located via OmicsDI, which aggregates across omics repositories; this record comes from metabolomics_workbench. Only repositories with no other discovery route in this project and with a working accession resolver are curated from OmicsDI -- GEO, ArrayExpress, PRIDE, MetaboLights and EGA hits are excluded as duplicates of dedicated passes. Matched because the disease is named in the dataset's own title ("Myalgic Encephalomyelitis/Chronic Fatigue Syndrome"). Retrieved 2026-08-02. Accession reverified on 2026-09-04. Dataset records or repeated samples are not necessarily independent participants. Provider-report citation does not establish that OpenScientist downloaded or analyzed this dataset.
- accession: metabolomics_workbench:ST000813
  title: Insights into myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) phenotypes through comprehensive metabolomics (part IV)
  notes: Located via OmicsDI, which aggregates across omics repositories; this record comes from metabolomics_workbench. Only repositories with no other discovery route in this project and with a working accession resolver are curated from OmicsDI -- GEO, ArrayExpress, PRIDE, MetaboLights and EGA hits are excluded as duplicates of dedicated passes. Matched because the disease is named in the dataset's own title ("Myalgic Encephalomyelitis/Chronic Fatigue Syndrome"). Retrieved 2026-08-02. Accession reverified on 2026-09-04. Dataset records or repeated samples are not necessarily independent participants. Provider-report citation does not establish that OpenScientist downloaded or analyzed this dataset.
- accession: metabolomics_workbench:ST000802
  title: Insights into myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) phenotypes through comprehensive metabolomics (part III))
  notes: Located via OmicsDI, which aggregates across omics repositories; this record comes from metabolomics_workbench. Only repositories with no other discovery route in this project and with a working accession resolver are curated from OmicsDI -- GEO, ArrayExpress, PRIDE, MetaboLights and EGA hits are excluded as duplicates of dedicated passes. Matched because the disease is named in the dataset's own title ("Myalgic Encephalomyelitis/Chronic Fatigue Syndrome"). Retrieved 2026-08-02. Accession reverified on 2026-09-04. Dataset records or repeated samples are not necessarily independent participants. Provider-report citation does not establish that OpenScientist downloaded or analyzed this dataset.
diagnosis:
- name: Clinical Symptom and Functional Assessment
  description: 'Document pre-illness function, the delayed response to physical and cognitive activity, sleep, cognition, upright symptoms and duration. A symptom/activity diary can help. CDC/NAM-style criteria require at least six months of substantial functional impairment with fatigue, PEM and unrefreshing sleep, plus cognitive impairment or orthostatic intolerance (or both). NICE permits diagnosis after three months and requires all four domains: debilitating fatigue, PEM, unrefreshing sleep or sleep disturbance, and cognitive difficulties; OI is an additional feature. In either approach assess other explanations and coexisting conditions, and start symptom care while evaluation continues.'
  evidence:
  - reference: url:https://www.cdc.gov/me-cfs/hcp/diagnosis/index.html
    reference_title: Diagnosing ME/CFS | ME/CFS | CDC
    supports: SUPPORT
    evidence_source: OTHER
    snippet: A thorough medical history, physical (including neurological) and mental health exam, and laboratory testing should be performed.
    explanation: CDC diagnostic approach requires clinical assessment and differential evaluation; the adjacent symptom list specifies PEM, sleep and cognitive/orthostatic features.
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: that have persisted for 3 months and are not explained by another condition.
    explanation: NICE diagnostic duration differs from the NAM-style six-month threshold.
- name: Evaluation for Alternative and Coexisting Conditions
  description: Use history, examination and targeted investigations rather than a universal exhaustive test panel. NICE examples include urinalysis, blood count, electrolytes, liver and thyroid tests, inflammatory markers, calcium/phosphate, HbA1c, ferritin, coeliac screening and creatine kinase; add B12/folate, vitamin D, infection tests or morning cortisol when indicated. Evaluate sleep disorders, medication effects, anemia, endocrine, inflammatory, neuromuscular and mental-health conditions as appropriate; comorbidities can coexist with ME/CFS.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: investigations to exclude other diagnoses
    explanation: NICE lists baseline investigations and clinical-judgment additions.
  - reference: url:https://www.cdc.gov/me-cfs/hcp/diagnosis/index.html
    reference_title: Diagnosing ME/CFS | ME/CFS | CDC
    supports: SUPPORT
    evidence_source: OTHER
    snippet: These steps are crucial to evaluate for other conditions that may explain symptoms.
    explanation: Differential assessment precedes diagnosis and continues during follow-up.
- name: Orthostatic Assessment
  description: Record upright symptoms and heart rate/blood pressure, using an adapted standing or specialist tilt assessment when clinically indicated and tolerated. Normal HR/BP does not rule out OI. Doppler cerebral-flow assays are research/specialist methods, not mandatory diagnostic tests.
  evidence:
  - reference: PMID:32140630
    reference_title: 'Cerebral blood flow is reduced in ME/CFS during head-up tilt testing even in the absence of hypotension or tachycardia: A quantitative, controlled study using Doppler echography.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: During HUT, extracranial Doppler measurements demonstrate that CBF is reduced in ME/CFS patients with POTS, dOH, and even in those without HR/BP abnormalities.
    explanation: Specialty cohort of 429 cases and 44 controls; normal orthostatic heart rate and blood pressure do not exclude OI. Referral prevalence is not population prevalence.
  - reference: PMID:41576003
    reference_title: Shared autonomic phenotype of long COVID and myalgic encephalomyelitis/chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: reduced orthostatic CBFv (92%/88% in Long COVID/ME/CFS)
    explanation: This retrospective autonomic-referral cohort measures cerebral blood-flow velocity, not volumetric flow; it does not establish a muscle-to-brain causal pathway.
- name: Biomarker and Exercise-Test Limitations
  description: There is no confirmatory blood, imaging, genetic or exercise test. NK function, cytokines, metabolomics, sodium MRI and commercial ATP profiles are not established diagnostic assays. Two-day CPET can characterize impairment in selected research or specialist settings but is not required for diagnosis; it can provoke prolonged worsening, especially in severe disease, and a negative day-two decline does not exclude PEM.
  evidence:
  - reference: url:https://www.cdc.gov/me-cfs/hcp/diagnosis/index.html
    reference_title: Diagnosing ME/CFS | ME/CFS | CDC
    supports: SUPPORT
    evidence_source: OTHER
    snippet: There is no confirmatory test currently available to diagnose ME/CFS.
    explanation: CDC distinguishes biological abnormalities from diagnostic validation.
  - reference: PMID:31391529
    reference_title: Assessing cellular energy dysfunction in CFS/ME using a commercially available laboratory test.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The MES test does not have the reliability and reproducibility required of a diagnostic test and therefore should not currently be offered as a diagnostic test for CFS/ME.
    explanation: Independent ten-case/thirteen-control replication failed; sample-processing delay substantially affected the score.
  - reference: PMID:38965566
    reference_title: 'Cardiopulmonary and metabolic responses during a 2-day CPET in myalgic encephalomyelitis/chronic fatigue syndrome: translating reduced oxygen consumption to impairment status to treatment considerations.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Abnormal post-exertional CPET responses persisted compared to CTL matched for aerobic capacity, indicating that fitness level does not predispose to exertion intolerance in ME/CFS.
    explanation: 'Canadian-criteria study: 84 cases and 71 sedentary controls, with 55 matched pairs; supports impaired recovery in this cohort.'
  - reference: PMID:42212259
    reference_title: Cardiopulmonary exercise test results do not change over two sequential days in patients with chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The data do not support using the 2-day CPET protocol to define PEM or disability.
    explanation: The 58-case and 25-control study required PEM and found no day-two VO2 decline. Absence of this physiological pattern does not exclude symptom-defined PEM or disability.
- name: Longitudinal Review
  description: Review symptoms, nutrition, function, medication effects and coexisting conditions regularly, adapting access to severity. Investigate new or changing symptoms rather than attributing every finding to ME/CFS.
  evidence:
  - reference: url:https://www.cdc.gov/me-cfs/hcp/diagnosis/index.html
    reference_title: Diagnosing ME/CFS | ME/CFS | CDC
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Patients with ME/CFS should be re-evaluated periodically.
    explanation: Continued assessment and usual preventive care remain appropriate.
clinical_trials:
- name: NCT06366724
  description: 'LIFT: Life Improvement Trial'
  status: RECRUITING
  phase: PHASE_II
  notes: Target 160 participants with ME/CFS and orthostatic intolerance. LIFT tests pyridostigmine and low-dose naltrexone; the 2026 publication is a protocol, not an efficacy result. Registry checked 2026-09-04.
  evidence:
  - reference: clinicaltrials:NCT06366724
    reference_title: 'LIFT: Life Improvement Trial'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: The LIFT will be conducted at Brigham and Women's Hospital (BWH) of Harvard Medical School, focusing on the effect of Pyridostigmine (Mestinon) and Low-Dose Naltrexone (LDN) in subjects aged 18-70 meeting the Canadian consensus criteria (CCC) for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) as well as having specifically Orthostatic Intolerance (OI).
    explanation: Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.
- name: NCT03674541
  description: The Exercise Response to Pharmacologic Cholinergic Stimulation in Myalgic Encephalomyelitis / Chronic Fatigue Syndrome
  status: COMPLETED
  phase: PHASE_II
  notes: Completed acute 45-person mechanistic trial, with two iCPETs 50 minutes apart; it does not assess a 24–72-hour PEM trajectory or durable response. Registry checked 2026-09-04.
  evidence:
  - reference: clinicaltrials:NCT03674541
    reference_title: The Exercise Response to Pharmacologic Cholinergic Stimulation in Myalgic Encephalomyelitis / Chronic Fatigue Syndrome
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Myalgic encephalomyelitis/Chronic fatigue syndrome (ME/CFS), otherwise known as Chronic fatigue syndrome (CFS) or myalgic encephalomyelitis (ME), is an under-recognized disorder whose cause is not yet understood.
    explanation: Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.
- name: NCT07285473
  description: 'Low-Dose Naltrexone For ME/CFS: Dose-Finding'
  status: NOT_RECRUITING
  phase: PHASE_II
  notes: Registered target 75; dose-finding study, not yet recruiting and no posted outcomes at the review date. Registry checked 2026-09-04. Exact registry status is NOT_YET_RECRUITING; schema uses NOT_RECRUITING.
  evidence:
  - reference: clinicaltrials:NCT07285473
    reference_title: 'Low-dose Naltrexone (LDN) for the Treatment of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): Dose-Finding'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: This exploratory clinical trial tests low-dose naltrexone (LDN) for the treatment of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).
    explanation: Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.
- name: NCT02229942
  description: B-lymphocyte Depletion Using Rituximab in Chronic Fatigue Syndrome/ Myalgic Encephalopathy (CFS/ME). A Randomized Phase-III Study.
  status: COMPLETED
  phase: PHASE_III
  notes: Completed 151-participant RituxME trial; primary publication reports no clinical benefit over placebo. Registry checked 2026-09-04.
  evidence:
  - reference: clinicaltrials:NCT02229942
    reference_title: B-lymphocyte Depletion Using the Monoclonal Anti-CD20 Antibody Rituximab in Chronic Fatigue Syndrome/ Myalgic Encephalopathy (CFS/ME). A Multicentre, Randomized, Double-blind and Placebo Controlled Phase-III Study With Rituximab Induction and Maintenance Treatment.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: The hypothesis is that a subgroup of patients with Chronic Fatigue Syndrome/ Myalgic Encephalopathy (CFS/ME) have a chronically activated immune system and may benefit from B-lymphocyte treatment using the monoclonal anti-CD20 antibody rituximab with induction and maintenance treatment.
    explanation: Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.
- name: NCT02444091
  description: Cyclophosphamide in Myalgic Encephalopathy/ Chronic Fatigue Syndrome (ME/CFS)
  status: COMPLETED
  phase: PHASE_II
  notes: Completed 40-participant open-label CycloME study; improvement cannot be attributed causally without a control arm. Registry checked 2026-09-04.
  evidence:
  - reference: clinicaltrials:NCT02444091
    reference_title: 'Cyclophosphamide in Myalgic Encephalopathy/ Chronic Fatigue Syndrome (ME/CFS). Part A: an Open Label Phase-II Study With Six Intravenous Cyclophosphamide Infusions Four Weeks Apart, and Follow-up for 12 Months'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Significant clinical improvements of ME/CFS symptoms were observed in two patients with long-standing ME/CFS who received adjuvant chemotherapy including cyclophosphamide for breast cancer, also in one ME/CFS patient who received chemotherapy including iphosphamide for Hodgkin lymphoma.
    explanation: Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.
- name: NCT04026425
  description: Analysis of Post-exertional Malaise Using a Two-day CPET in People With ME/CFS
  status: COMPLETED
  phase: NOT_APPLICABLE
  notes: Observational exercise study, registry enrollment 173; the 2024 two-day analysis included 84 cases and 71 controls. Registry total and analyzed subsets are different denominators. Registry checked 2026-09-04.
  evidence:
  - reference: clinicaltrials:NCT04026425
    reference_title: Probing Metabolism, Circulating Inflammatory Molecules, Extracellular Vesicles and Immune Dysregulation in Individual Immune Cells in ME/CFS
    supports: SUPPORT
    evidence_source: OTHER
    snippet: This study aims to collect and identify key outcome measures or disease parameters in ME/CFS that are altered during elevated symptoms relative to baseline by gathering information before and after symptom provocation using a two-day cardiopulmonary exercise test.
    explanation: Registry summary supports identity and design; status was separately checked against the ClinicalTrials.gov API on 2026-09-04.
has_subtypes:
- name: Mild ME/CFS
  description: Able to manage personal care and some domestic activity, often with reduced hours and loss of leisure or social activity. These NICE severity grades can fluctuate; they are not etiologic categories.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: People with mild ME/CFS care for themselves
    explanation: NICE severity definitions guide support needs.
- name: Moderate ME/CFS
  description: Reduced mobility and restricted daily activities, usually unable to continue work or education and requiring daytime rest. These NICE severity grades can fluctuate; they are not etiologic categories.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: People with moderate ME/CFS have reduced mobility
    explanation: NICE severity definitions guide support needs.
- name: Severe ME/CFS
  description: Minimal self-care, major cognitive and sensory burden, often housebound or predominantly bedbound. These NICE severity grades can fluctuate; they are not etiologic categories.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: They may also spend most of their time in bed
    explanation: NICE severity definitions guide support needs.
- name: Very Severe ME/CFS
  description: Bedbound and dependent on care, with marked sensory intolerance and sometimes inability to swallow. These NICE severity grades can fluctuate; they are not etiologic categories.
  evidence:
  - reference: url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations
    reference_title: 'Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management  | Guidance | NICE'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: are in bed all day and dependent on care.
    explanation: NICE severity definitions guide support needs.
animal_models:
- name: Atg13-Depleted Mouse
  species: Mus musculus
  genotype: Tg+/-ATG13
  description: Heterozygous Atg13 depletion connects impaired autophagy, oxidative metabolism, macrophage polarization and muscle-nerve abnormalities. Treadmill weakness does not establish human symptom-defined PEM, disease-specific genetics or the full perfusion pathway.
  publication: PMID:41591477
  evidence:
  - reference: PMID:41591477
    reference_title: Genetic depletion of the early autophagy protein ATG13 impairs mitochondrial energy metabolism, augments oxidative stress, induces the polarization of macrophages to the M1 inflammatory mode, and compromises myelin integrity in skeletal muscle.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: ablation of the atg13 gene resulted in increased infiltration of M1Mφs into the muscle vasculature, deterioration of myelin integrity in nerve bundles, and a reduction in muscle strength following treadmill exercise.
    explanation: Genetically depleted mouse model supports autophagy-macrophage-muscle coupling; human ME/CFS ATG13 causation is unproven.
  modeled_mechanisms:
  - target: Autophagy-Associated Macrophage Dysfunction
    description: Atg13 depletion tests coupling of autophagy, macrophage activation and post-exercise muscle/nerve injury in mice.
    evidence:
    - reference: PMID:41591477
      reference_title: Genetic depletion of the early autophagy protein ATG13 impairs mitochondrial energy metabolism, augments oxidative stress, induces the polarization of macrophages to the M1 inflammatory mode, and compromises myelin integrity in skeletal muscle.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: ablation of the atg13 gene resulted in increased infiltration of M1Mφs into the muscle vasculature, deterioration of myelin integrity in nerve bundles, and a reduction in muscle strength following treadmill exercise.
      explanation: Genetically depleted mouse model supports autophagy-macrophage-muscle coupling; human ME/CFS ATG13 causation is unproven.
    relationship: PERTURBS
experimental_models:
- name: Patient-Derived Skeletal Myotubes
  experimental_model_type: PRIMARY_CELL_CULTURE
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  description: Nine CFS and eleven control donors; glucose-linked oxidative metabolism differed while galactose and fatty-acid use were preserved. Culture retention does not distinguish genetic from persistent epigenetic effects.
  evidence:
  - reference: PMID:33106563
    reference_title: Substrate utilisation of cultured skeletal muscle cells in patients with CFS.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: galactose and fatty acids normally, indicating that the bioenergetic dysfunction lies upstream of the TCA cycle.
    explanation: Cultured myotubes from nine CFS and eleven control donors had substrate-dependent glucose-use abnormalities; persistence in culture is not proof of a genetic defect.
  modeled_mechanisms:
  - target: Skeletal Muscle Bioenergetic Disturbance
    description: Patient-derived myotubes show impaired glucose oxidation with preserved galactose and fatty-acid oxidation in substrate-specific culture assays.
    evidence:
    - reference: PMID:33106563
      reference_title: Substrate utilisation of cultured skeletal muscle cells in patients with CFS.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: galactose and fatty acids normally, indicating that the bioenergetic dysfunction lies upstream of the TCA cycle.
      explanation: Cultured myotubes from nine CFS and eleven control donors had substrate-dependent glucose-use abnormalities; persistence in culture is not proof of a genetic defect.
    relationship: MEASURES
- name: Patient NK-Cell TRPM3 Assays
  experimental_model_type: PRIMARY_CELL_CULTURE
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  description: Electrophysiology with pregnenolone sulfate, ononetin and naltrexone; later live-cell cytosolic/mitochondrial calcium assays. Ex vivo target modulation is not clinical drug efficacy.
  evidence:
  - reference: PMID:31736966
    reference_title: Naltrexone Restores Impaired Transient Receptor Potential Melastatin 3 Ion Channel Function in Natural Killer Cells From Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: TRPM3 channel activity was restored in IL-2 stimulated NK cells isolated from ME/CFS patients after incubation for 24 h with NTX.
    explanation: Eight patient and eight control donors; ex vivo rescue does not demonstrate improvement of autonomic symptoms or PEM.
  - reference: PMID:42177403
    reference_title: Deficient TRPM3-linked mitochondrial Ca(2+) influx in natural killer cells associated with myalgic encephalomyelitis/chronic fatigue syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Cytosolic Ca2+ influx amplitude and slope were significantly reduced (p < 0.001), with a significantly shorter T1/2 response (p = 0.001) in ME/CFS compared to HC. Ca2+ influx amplitude (p < 0.001) and slope (p < 0.041) into the mitochondria were significantly higher in ME/CFS compared to HC. TRPM3 activation triggered pronounced cytosolic response (P < 0.001) accompanied by mitochondrial Ca2+ increase in HC. TRPM3-dependent cytosolic and mitochondrial Ca2+ mobilisation (P < 0.015) were significantly reduced with a shorter T1/2 response (p < 0.02) in ME/CFS compared to HC.
    explanation: 'Ten cases and ten controls: calcium re-addition produced higher mitochondrial influx despite lower cytosolic response, whereas pregnenolone-sulfate/TRPM3-dependent cytosolic and mitochondrial responses were both reduced. These are stimulus-specific NK-cell assays, not muscle calcium measurements.'
  modeled_mechanisms:
  - target: TRPM3-Associated NK-Cell Calcium Dysregulation
    description: Patch-clamp and compartment-specific calcium measurements identify condition-dependent NK-cell abnormalities; IL-2/naltrexone experiments test ex vivo channel rescue.
    evidence:
    - reference: PMID:31736966
      reference_title: Naltrexone Restores Impaired Transient Receptor Potential Melastatin 3 Ion Channel Function in Natural Killer Cells From Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: TRPM3 channel activity was restored in IL-2 stimulated NK cells isolated from ME/CFS patients after incubation for 24 h with NTX.
      explanation: Eight patient and eight control donors; ex vivo rescue does not demonstrate improvement of autonomic symptoms or PEM.
    - reference: PMID:42177403
      reference_title: Deficient TRPM3-linked mitochondrial Ca(2+) influx in natural killer cells associated with myalgic encephalomyelitis/chronic fatigue syndrome.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Cytosolic Ca2+ influx amplitude and slope were significantly reduced (p < 0.001), with a significantly shorter T1/2 response (p = 0.001) in ME/CFS compared to HC. Ca2+ influx amplitude (p < 0.001) and slope (p < 0.041) into the mitochondria were significantly higher in ME/CFS compared to HC. TRPM3 activation triggered pronounced cytosolic response (P < 0.001) accompanied by mitochondrial Ca2+ increase in HC. TRPM3-dependent cytosolic and mitochondrial Ca2+ mobilisation (P < 0.015) were significantly reduced with a shorter T1/2 response (p < 0.02) in ME/CFS compared to HC.
      explanation: 'Ten cases and ten controls: calcium re-addition produced higher mitochondrial influx despite lower cytosolic response, whereas pregnenolone-sulfate/TRPM3-dependent cytosolic and mitochondrial responses were both reduced. These are stimulus-specific NK-cell assays, not muscle calcium measurements.'
    relationship: MEASURES
- name: Patient T-Cell Metabolic Assays
  experimental_model_type: PRIMARY_CELL_CULTURE
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  description: Resting and activated CD4/CD8 cells from 53 cases and 45 controls; glycolytic flux and membrane-potential assays.
  evidence:
  - reference: PMID:31830003
    reference_title: Myalgic encephalomyelitis/chronic fatigue syndrome patients exhibit altered T cell metabolism and cytokine associations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Both CD4+ and CD8+ T cells from patients with ME/CFS had reduced glycolysis at rest, whereas CD8+ T cells also had reduced glycolysis following activation.
    explanation: Primary patient-cell metabolism study with 53 cases and 45 controls; this does not establish universal mitochondrial respiratory failure.
  modeled_mechanisms:
  - target: T-Cell Immunometabolic Dysfunction
    description: Resting CD4/CD8 and activated CD8 assays measure reduced glycolysis in patient cells; this does not establish global respiratory failure.
    evidence:
    - reference: PMID:31830003
      reference_title: Myalgic encephalomyelitis/chronic fatigue syndrome patients exhibit altered T cell metabolism and cytokine associations.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Both CD4+ and CD8+ T cells from patients with ME/CFS had reduced glycolysis at rest, whereas CD8+ T cells also had reduced glycolysis following activation.
      explanation: Primary patient-cell metabolism study with 53 cases and 45 controls; this does not establish universal mitochondrial respiratory failure.
    relationship: MEASURES
- name: Erythrocyte Microfluidic Deformability Assay
  experimental_model_type: OTHER
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  description: Sixteen case-control pairs studied outside the body; channel transit measures do not establish in vivo capillary obstruction.
  evidence:
  - reference: PMID:30594919
    reference_title: Red blood cell deformability is diminished in patients with Chronic Fatigue Syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: We observed from various measures of deformability that the RBCs isolated from ME/CFS patients were significantly stiffer than those from healthy controls.
    explanation: Sixteen case-control pairs tested in a microfluidic device; the proposed in vivo perfusion consequence and diagnostic performance remain unvalidated.
  modeled_mechanisms:
  - target: Reduced Erythrocyte Deformability
    description: Microfluidic transit assays measure altered deformability of patient erythrocytes.
    evidence:
    - reference: PMID:30594919
      reference_title: Red blood cell deformability is diminished in patients with Chronic Fatigue Syndrome.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: We observed from various measures of deformability that the RBCs isolated from ME/CFS patients were significantly stiffer than those from healthy controls.
      explanation: Sixteen case-control pairs tested in a microfluidic device; the proposed in vivo perfusion consequence and diagnostic performance remain unvalidated.
    relationship: MEASURES
- name: Patient Serum Vesicle-Microglia Assay
  experimental_model_type: CELL_LINE
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  description: Human HM-SV40 microglia exposed to patient serum extracellular-vesicle preparations, with IL-1beta release as a readout. Published abstract and figure captions support bioactivity; detailed pooling/isolation information is available in the earlier author preprint, and final-version full methods were not accessible. Cargo identity, muscle origin and BBB crossing were not established.
  evidence:
  - reference: PMID:36153118
    reference_title: Exosome-associated mitochondrial DNA from patients with myalgic encephalomyelitis/chronic fatigue syndrome stimulates human microglia to release IL-1β.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Moreover, exosomes isolated from patients with ME/CFS stimulate significant release of IL-1β from cultured human microglia.
    explanation: Patient serum vesicle preparations have in vitro bioactivity. This does not establish mtDNA necessity, muscle origin, BBB passage or human brain inflammation.
  modeled_mechanisms:
  - target: Proposed Peripheral Vesicle-Microglial Signaling
    relationship: PERTURBS
    description: Adding patient vesicle preparations elicits a cultured microglial cytokine response.
    limitations: An immortalized cell assay does not reproduce brain exposure in vivo. Vesicle-preparation effects do not isolate mtDNA from other cargo or copurified material.
    evidence:
    - reference: PMID:36153118
      reference_title: Exosome-associated mitochondrial DNA from patients with myalgic encephalomyelitis/chronic fatigue syndrome stimulates human microglia to release IL-1β.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Moreover, exosomes isolated from patients with ME/CFS stimulate significant release of IL-1β from cultured human microglia.
      explanation: Patient serum vesicle preparations have in vitro bioactivity. This does not establish mtDNA necessity, muscle origin, BBB passage or human brain inflammation.
updated_date: '2026-09-05T00:10:32Z'

📚

References & Deep Research

References

DOI:10.1126/science.abo1261

Understanding myalgic encephalomyelitis

No top-level findings curated for this source.

DOI:10.3389/fimmu.2024.1386607

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: the biology of a neglected disease

No top-level findings curated for this source.

DOI:10.3389/fneur.2022.877772

Molecular Mechanisms of Neuroinflammation in ME/CFS and Long COVID to Sustain Disease and Promote Relapses

No top-level findings curated for this source.

url:https://www.nice.org.uk/guidance/ng206/chapter/Recommendations

Recommendations | Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management | Guidance | NICE

No top-level findings curated for this source.

url:https://www.cdc.gov/me-cfs/hcp/diagnosis/index.html

Diagnosing ME/CFS | ME/CFS | CDC

No top-level findings curated for this source.

Deep Research

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Disorder ▸

Disorder

Name: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome
Category: Complex
Existing deep-research providers: falcon
Existing evidence reference count in YAML: 27

Key Pathophysiology Nodes

Innate Immune Hyperreactivity
Natural Killer Cell Dysfunction
T-Cell Immunometabolic Dysfunction
Endothelial Dysfunction and Coagulopathy
TRPM3 Ion Channel Dysfunction
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Disease Pathophysiology Research Template

Edison Scientific Literature 29 citations 2026-03-17T18:47:43.481902

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Pathophysiology Research Template

Target Disease

Disease Name: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome
MONDO ID: (if available)
Category: Complex

Research Objectives

Please provide a comprehensive research report on the pathophysiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Focus on the molecular and cellular mechanisms underlying disease progression.

Required Information

1. Core Pathophysiology

What are the primary pathophysiological mechanisms?
What molecular pathways are dysregulated?
What cellular processes are affected?

2. Key Molecular Players

Genes/Proteins: Which genes are causally involved or implicated?
Chemical Entities: What metabolites, drugs, or small molecules are relevant?
Cell Types: Which cell types are primarily affected?
Anatomical Locations: Which tissues/organs are involved?

3. Biological Processes (for GO annotation)

What biological processes (GO terms) are disrupted?
Consider: signaling pathways, metabolic processes, cellular responses, transport, etc.

4. Cellular Components

Where in the cell do key processes occur?
Consider: organelles, membrane compartments, extracellular space, etc.

5. Disease Progression

What is the sequence of events from initial trigger to clinical manifestation?
Are there distinct stages or phases?

6. Phenotypic Manifestations

What are the key clinical phenotypes?
How do they relate to the underlying mechanisms?

Citation Requirements

Cite primary literature (PMID preferred) for all mechanistic claims
Prioritize recent reviews and landmark papers
Include direct quotes where possible to support key statements

Output Format

Structure your response as a narrative that could be used to populate a disease knowledge base entry with: - Pathophysiology description - Gene/protein annotations with ontology terms (HGNC, GO) - Phenotype associations (HP terms) - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Evidence items with PMIDs

Research report: Pathophysiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

Disease entity and scope

Disease: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).
Category: Complex, multisystem disorder characterized clinically by post-exertional symptom exacerbation (often termed post-exertional malaise; PEM) and heterogeneous neurological, autonomic, immune, and metabolic manifestations. Recent syntheses emphasize a multifactorial, network-like pathophysiology arising from genetic vulnerability plus environmental triggers (commonly infections) that converge on persistent immune dysregulation, autonomic dysfunction, metabolic disturbances, and (in some cohorts) vascular/endothelial and coagulation abnormalities. (arron2024myalgicencephalomyelitischronicfatigue pages 1-2, walitt2024deepphenotypingof pages 1-2)

MONDO ID: Not retrieved in the current evidence set.

1) Core pathophysiology (current understanding)

1.1 Immune dysregulation and chronic antigenic stimulation

A consistent theme across recent high-quality studies is chronic immune perturbation compatible with persistent antigenic stimulation.

B-cell compartment shifts (post-infectious ME/CFS): Deep phenotyping of a rigorously adjudicated post-infectious cohort reported an “increase in naïve and decrease in switched memory B-cells,” interpreted as evidence consistent with chronic antigenic stimulation. (walitt2024deepphenotypingof pages 1-2)
Natural killer (NK) cell dysfunction (most reproducible immune phenotype): A 2024 registered meta-analysis of NK cytotoxicity across 28 papers (55 effector:target datapoints) found NK cytotoxicity in ME/CFS was reduced to about half of healthy control levels, with an overall effect size Hedges’ g = 0.96 (95% CI 0.75–1.18). (baraniuk2024metaanalysisofnatural pages 1-2)
T-cell exhaustion programs (emerging 2024 theme): Multi-omic analyses of CD8+ T cells support epigenetic/transcriptional priming toward exhaustion, with exhaustion markers reportedly upregulated after exercise provocation, consistent with chronic antigen exposure models (e.g., persistent/latent viral drivers as one plausible upstream contributor). (iu2024transcriptionalreprogrammingprimes pages 1-2)

Interpretation: Immune phenotypes span innate cytotoxic impairment (NK), adaptive exhaustion-like programs (CD8), and altered memory differentiation (B-cells). Together, these can plausibly reduce pathogen control (or promote antigen persistence), while also sustaining inflammatory signaling that couples to autonomic and metabolic dysfunction. (baraniuk2024metaanalysisofnatural pages 1-2, walitt2024deepphenotypingof pages 1-2, iu2024transcriptionalreprogrammingprimes pages 1-2)

1.2 Autonomic nervous system (ANS) dysregulation and neurovascular consequences

Autonomic abnormalities are prominent in recent physiologic profiling.

In post-infectious ME/CFS deep phenotyping, autonomic testing supported altered sympathetic/parasympathetic features, including prolonged blood pressure recovery after Valsalva (4.1 ± 0.4 s vs 3.0 ± 0.2 s in controls; p = 0.014). (walitt2024deepphenotypingof pages 1-2)
Orthostatic intolerance and cerebral blood flow (CBF) abnormalities are described as common, with one synthesis reporting that 90% (384/429) exceeded a 13% CBF reduction cutoff, with mean CBF reduction 26% vs 7% in controls, and substantial rates of orthostatic symptoms (e.g., 72% [32/39] light-headedness on standing). (nunes2024assessingthecoagulation pages 33-36)
In a 2024 prospective pilot cohort that compared ME/CFS, long COVID, and controls, POTS was identified during a 10-min NASA lean test in 13% (4/31) of ME/CFS participants. (graves2024chronicfatiguesyndrome pages 5-7)

Interpretation: ANS dysregulation provides a mechanistic bridge from immune/inflammatory signaling to impaired perfusion regulation, symptom flares with orthostatic or exertional stress, and downstream energy limitation. (walitt2024deepphenotypingof pages 1-2, nunes2024assessingthecoagulation pages 33-36, graves2024chronicfatiguesyndrome pages 5-7)

1.3 Endothelial dysfunction, coagulation pathway disturbance, and complement downregulation

Multiple recent datasets implicate vascular/endothelial and coagulation biology.

Endothelial biomarkers and inflammation: ME/CFS and long COVID groups showed higher ET-1 and VCAM-1 and lower nitrite/nitrate (NOx) than controls; ME/CFS additionally showed higher PAI-1 and E-selectin than both long COVID and controls (p-values reported in the study abstract). (graves2024chronicfatiguesyndrome pages 5-7)
Plasma proteomics (DIA LC-MS/MS): In platelet-poor plasma from 15 ME/CFS vs 10 controls, 45 proteins were differentially expressed (24 up, 21 down; p < 0.05). Large-magnitude examples include lactotransferrin up to 8.38-fold (p = 0.00009), thrombospondin-1 ~3.48–3.75-fold (p ≤ 0.0002), platelet factor 4 3.11-fold (p = 0.00009), protein S 0.48-fold (p = 0.0006), and complement C9 0.17-fold (p = 0.0001). (nunes2024dataindependentlcmsmsanalysis pages 5-7)

Interpretation: These patterns support a model in which endothelial activation/dysfunction and platelet/coagulation signaling contribute to impaired oxygen/nutrient delivery under stress and may interact with inflammatory tone and autonomic dysregulation. Complement downregulation (e.g., C9) may reflect altered innate effector pathways or chronic immune modulation. (nunes2024dataindependentlcmsmsanalysis pages 5-7, graves2024chronicfatiguesyndrome pages 5-7)

1.4 Neurological dysfunction and neuroaxonal injury signals

Neurological impairment is core to patient experience (“brain fog,” cognitive dysfunction) and is increasingly probed using blood biomarkers.

Plasma neurofilament light chain (NfL): In 67 ME/CFS vs 43 controls, NfL was higher in ME/CFS (F = 4.30, p < 0.05) and correlated with worse cognition (visuospatial perception r = −0.42, p ≤ 0.001; verbal memory r = −0.35, p ≤ 0.005; visual memory r = −0.26, p < 0.05). NfL explained up to 17.2% of variance in cognitive tests and associated with parasympathetic dysfunction (F = 9.48, p ≤ 0.003). (azcue2024plasmaneurofilamentlight pages 1-2)
Central catechol pathway dysregulation hypothesis (deep phenotyping): Behavioral findings (altered effort preference) were linked to dysfunction of integrative brain regions and “central catechol pathway dysregulation,” consistent with a brain–autonomic–immune interface model. (walitt2024deepphenotypingof pages 1-2)

Interpretation: NfL provides convergent evidence for measurable neuroaxonal injury/stress in a subset and supports integrating central nervous system involvement into mechanistic models alongside ANS and immune alterations. (azcue2024plasmaneurofilamentlight pages 1-2, walitt2024deepphenotypingof pages 1-2)

1.5 Metabolic/mitochondrial dysfunction and the “energy limitation” phenotype

Recent reviews and multi-omic studies consistently emphasize metabolic disturbance as a contributor to exertion intolerance.

A 2024 synthesis frames ME/CFS as involving metabolic disturbances alongside immune dysregulation, inflammation, and gut dysbiosis, supporting an integrated “systems” model rather than single-pathway causation. (arron2024myalgicencephalomyelitischronicfatigue pages 1-2)
Deep phenotyping reported alterations in PBMC gene expression and metabolic pathways (with sex-specific differences), consistent with immune–metabolic coupling. (walitt2024deepphenotypingof pages 1-2)

Interpretation: While the mechanistic target is not yet unified, metabolic reprogramming appears to be a downstream integrator of immune and neurovascular stressors—particularly relevant to PEM. (walitt2024deepphenotypingof pages 1-2, arron2024myalgicencephalomyelitischronicfatigue pages 1-2)

1.6 Microbiome and gut–immune interactions

Several contemporary reviews highlight gut dysbiosis and reduced short-chain fatty acid (SCFA) production as plausible amplifiers of systemic inflammation and metabolic dysfunction, though cohort-specific causality remains unresolved in the evidence excerpts available here. (graves2024chronicfatiguesyndrome pages 4-5, graves2024chronicfatiguesyndrome pages 5-7)

2) Recent developments (prioritizing 2023–2024)

2.1 Deep phenotyping defines candidate mechanistic axes (2024)

A major 2024 advance is the use of rigorous case adjudication plus broad deep phenotyping to link clinical signatures (including effort preference/behavioral changes) to autonomic function, immune profiles, and multi-omic differences in post-infectious ME/CFS. Key quantitative signals include Valsalva recovery differences (p = 0.014) and an effort-choice odds ratio (OR 1.65, p = 0.04). (walitt2024deepphenotypingof pages 1-2)

2.2 Endothelium–inflammation biomarker panels differentiate ME/CFS from long COVID (2024)

The prospective pilot cohort approach combining endothelial and inflammatory markers with symptom severity measures provides a step toward stratification and differential diagnosis, including a measurable POTS proportion under standardized orthostatic testing (13% in ME/CFS). (graves2024chronicfatiguesyndrome pages 5-7)

2.3 Plasma proteomics strengthens coagulation/endothelial/complement hypotheses (2024)

The 2024 DIA LC-MS/MS study provides explicit protein-level effect sizes supporting platelet activation (PF4), endothelial/coagulation regulation (THBS1, PROS1), and complement attenuation (C9), generating tractable biomarkers for replication and mechanistic follow-up. (nunes2024dataindependentlcmsmsanalysis pages 5-7)

2.4 Immune exhaustion and cytotoxic impairment are converging mechanistic themes (2024)

The NK cytotoxicity meta-analysis quantifies a robust innate defect across decades of literature (Hedges’ g 0.96), while multi-omic T-cell work is converging on exhaustion-like programs, especially in relation to symptom provocation (exercise). (baraniuk2024metaanalysisofnatural pages 1-2, iu2024transcriptionalreprogrammingprimes pages 1-2)

2.5 Neurological biomarker development: NfL as a candidate (2024)

NfL elevations and correlations with cognition and parasympathetic dysfunction nominate a measurable neurological axis and a potential stratification biomarker for clinical studies. (azcue2024plasmaneurofilamentlight pages 1-2)

3) Current applications and real-world implementations

3.1 Biomarker candidates under active investigation

Neuroaxonal injury marker: plasma NfL for neurological dysfunction and cognitive/autonomic correlation. (azcue2024plasmaneurofilamentlight pages 1-2)
Endothelial and inflammatory panels: ET-1, VCAM-1, NOx, cytokines/chemokines (e.g., TNF-α, IL-1β, IL-6) to support subtype differentiation and severity associations. (graves2024chronicfatiguesyndrome pages 5-7)
Proteomic biomarker set: THBS1, PF4, PROS1, C9, FCN3, LTF, S100A9 and others as candidate signatures of coagulation/endothelial/complement dysregulation. (nunes2024dataindependentlcmsmsanalysis pages 5-7)
Functional immune assay: NK cytotoxicity (and related degranulation pathways) remains a reproducible immune functional abnormality, useful as a mechanistic readout in trials. (baraniuk2024metaanalysisofnatural pages 1-2)

3.2 Mechanistically motivated interventions being tested

A randomized, placebo-controlled trial of intranasal mechanical stimulation (targeting a proposed brainstem neuro-immune interface) reported an approximately 30% reduction in overall symptom scores after 8 weeks, with immunologic correlates suggestive of reduced inflammation and increased disease tolerance programs. (rodriguez2023achievingsymptomrelief pages 1-2)

Caution: This intervention represents an experimental approach; the evidence excerpt does not establish long-term efficacy or generalizability. (rodriguez2023achievingsymptomrelief pages 1-2)

4) Expert synthesis and analysis (authoritative perspectives in the retrieved evidence)

4.1 “Multifactorial network” model

A 2024 immunology review argues for moving beyond fragmented single-mechanism explanations toward a cohesive model in which genetic predisposition plus environmental triggers (notably infections) lead to interconnected immune dysregulation, chronic inflammation, gut dysbiosis, and metabolic disturbance. (arron2024myalgicencephalomyelitischronicfatigue pages 1-2)

4.2 Disease burden and heterogeneity as a pathophysiology constraint

The same review compiles prevalence and socioeconomic burden estimates (e.g., global prevalence 0.1–0.8%; women affected 2–3×; up to 75% unable to work), reinforcing that heterogeneous phenotypes likely reflect multiple biological subtypes and/or phases—an important premise for interpreting inconsistent biomarker literature and for designing stratified studies. (arron2024myalgicencephalomyelitischronicfatigue pages 1-2)

4.3 Autoimmunity and post-transcriptional regulation: plausible but not definitive

Recent syntheses highlight potential roles for autoantibodies and miRNA dysregulation, but the evidence base remains heterogeneous and requires careful replication and phenotype definition; miRNAs repeatedly implicated across studies include miR-29c, miR-99b, miR-128, miR-374b, miR-766, and others linked to immune and mitochondrial/oxidative pathways. (tsamou2024identifyingmicrornaspossibly pages 1-2)

5) Key statistics and quantitative data points from recent studies

Deep phenotyping recruitment yield: 484 inquiries → 27 in-person evaluation → 17 adjudicated PI-ME/CFS cases. (walitt2024deepphenotypingof pages 1-2)
Autonomic physiology: Valsalva BP recovery 4.1 ± 0.4 s vs 3.0 ± 0.2 s, p = 0.014. (walitt2024deepphenotypingof pages 1-2)
Orthostatic cerebral blood flow synthesis: 90% (384/429) exceeded a 13% CBF reduction cutoff; mean reduction 26% vs 7% in controls (as reported in synthesis). (nunes2024assessingthecoagulation pages 33-36)
POTS rate under standardized test: ME/CFS 13% (4/31). (graves2024chronicfatiguesyndrome pages 5-7)
Proteomics: 45 proteins differential (24 up/21 down, p < 0.05); examples include THBS1 ~3.5–3.8× up; PF4 3.11× up; LTF 8.38× up; PROS1 0.48×; C9 0.17×. (nunes2024dataindependentlcmsmsanalysis pages 5-7)
NfL biomarker: higher in ME/CFS (F = 4.30, p < 0.05); cognitive correlations up to |r| = 0.42; variance explained up to 17.2%; autonomic parasympathetic association F = 9.48, p ≤ 0.003. (azcue2024plasmaneurofilamentlight pages 1-2)
NK cytotoxicity meta-analysis: Hedges’ g 0.96 (0.75–1.18); ~50% of control cytotoxicity level. (baraniuk2024metaanalysisofnatural pages 1-2)
INMEST trial: ~30% symptom reduction after 8 weeks (N = 31). (rodriguez2023achievingsymptomrelief pages 1-2)

Evidence map (recent, 2023–2024)

The following table provides a compact evidence map of recent mechanistic work and quantitative results.

Mechanistic domain	Key finding	Study (first author, year, journal)	Cohort/sample size	Quantitative results (stats)	Molecular/cellular entities (genes/proteins/metabolites/cell types)	URL/DOI
Multisystem deep phenotyping: immune, autonomic, central catechol/neurobehavioral	Post-infectious ME/CFS showed chronic antigenic stimulation with increased naïve and decreased switched-memory B cells, autonomic abnormalities, and altered effort preference consistent with dysfunction of integrative brain regions and central catechol pathway dysregulation	Walitt, 2024, Nature Communications	17 adjudicated PI-ME/CFS; 21 healthy volunteers; recruited from 484 inquiries and 27 in-person evaluations	Valsalva blood-pressure recovery time 4.1 ± 0.4 s vs 3.0 ± 0.2 s in controls, p = 0.014; altered effort choice OR 1.65 (95% CI 1.03–2.65), p = 0.04	Naïve B cells, switched memory B cells, catechol pathways, PBMC gene-expression/metabolic pathways	https://doi.org/10.1038/s41467-024-45107-3
Endothelial dysfunction + inflammatory signaling	ME/CFS showed a biomarker pattern consistent with endothelial dysfunction and systemic inflammation, distinct from long COVID but overlapping in ET-1/VCAM-1 elevation and NO metabolite reduction	Domingo, 2024, Journal of Translational Medicine	31 ME/CFS; 23 long COVID; 31 sedentary healthy controls	POTS on NASA lean test: 4/31 ME/CFS (13%), 1/23 long COVID (4%), 1/31 controls (3%); ME/CFS and long COVID had higher ET-1 (p < 0.05) and VCAM-1 (p < 0.001), lower NOx (p < 0.01); ME/CFS had higher PAI-1 and E-selectin than both comparison groups (p < 0.01); PCA PC1 82.7%, PC2 6.1%; combined biomarker classification ME/CFS vs long COVID 59%	ET-1/EDN1, VCAM1, ICAM1, SELE/E-selectin, SERPINE1/PAI-1, TNF, IL1B, IL4, IL6, IL10, CXCL10/IP-10, leptin	https://doi.org/10.1186/s12967-024-05148-0
Coagulation/endothelial/complement proteomics	Plasma proteomics implicated dysregulated coagulation, endothelial dysfunction, and complement downregulation in ME/CFS	Nunes, 2024, Cardiovascular Diabetology	15 ME/CFS; 10 controls	45 proteins significant at p < 0.05: 24 up, 21 down; thrombospondin-1 3.48–3.75-fold up (p ≤ 0.0002); PF4 3.11-fold up (p = 0.00009); lactotransferrin up to 8.38-fold up (p = 0.00009); protein S 0.48-fold (p = 0.0006); C9 0.17-fold (p = 0.0001); ficolin-3 ~0.45–0.65-fold (p = 0.0006–0.0348)	THBS1, PF4, PROS1, C9, FCN3, LTF, S100A9, IGHG1; platelet-poor plasma proteins	https://doi.org/10.1186/s12933-024-02315-x
Neurological dysfunction / neuroaxonal injury biomarker	Elevated plasma neurofilament light chain suggested neuroaxonal injury associated with cognitive impairment and autonomic dysfunction in ME/CFS	Azcue, 2024, Biomedicines	67 ME/CFS; 43 healthy controls	Higher plasma NfL in ME/CFS: F = 4.30, p < 0.05; correlations with visuospatial perception r = -0.42, p ≤ 0.001; verbal memory r = -0.35, p ≤ 0.005; visual memory r = -0.26, p < 0.05; parasympathetic dysfunction F = 9.48, p ≤ 0.003; NfL explained up to 17.2% of cognitive-test variance	NfL/NEFL, cognitive domains, parasympathetic/autonomic function	https://doi.org/10.3390/biomedicines12071539
Innate immune dysfunction	NK-cell cytotoxicity is one of the most reproducible immune abnormalities in ME/CFS	Baraniuk, 2024, Frontiers in Immunology	Meta-analysis of 28 papers; 55 effector:target data points	Overall Hedges’ g = 0.96 (95% CI 0.75–1.18); NK cytotoxicity reduced to about half of healthy-control levels; literature search yielded 522 records	NK cells, cytotoxicity assays, K562 target cells, lytic granule pathways	https://doi.org/10.3389/fimmu.2024.1440643
Neuro-immune interface / disease tolerance	Targeting the neuro-immune interface via intranasal mechanical stimulation was associated with symptom improvement and immunologic changes consistent with reduced inflammation and increased disease tolerance	Rodriguez, 2023, Oxford Open Immunology	31 ME patients (17 enrolled in 2018; 14 in 2019)	~30% reduction in overall symptom scores after 8 weeks; randomized, placebo-controlled treatment: 20 min twice weekly for 1 month	Brainstem, vagus nerve, trigeminal-related nasal nerve endings, T-cell subsets, gut-homing immune cells, inflammatory programs	https://doi.org/10.1093/oxfimm/iqad003
Integrative pathophysiology review	ME/CFS is framed as a multifactorial disease emerging from genetic vulnerabilities plus environmental triggers, especially infections, producing immune dysregulation, chronic inflammation, gut dysbiosis, autonomic abnormalities, and metabolic disturbance	Arron, 2024, Frontiers in Immunology	Review; epidemiologic synthesis	Global prevalence estimated 0.1–0.8%; women affected 2–3× more than men; up to 75% unable to work; estimated annual cost US $18–24B and UK £3.3B	Immune dysregulation, gut microbiome, metabolic pathways, autonomic nervous system, inflammatory networks	https://doi.org/10.3389/fimmu.2024.1386607
Post-transcriptional regulation / miRNA biology	Dysregulated miRNAs are linked to immune response, mitochondrial dysfunction, oxidative stress, and central sensitization in ME/CFS	Tsamou, 2024, International Journal of Molecular Sciences	Review	No pooled effect size reported in excerpt; review highlights repeatedly implicated candidates across studies	miR-29c, miR-99b, miR-128, miR-374b, miR-766, miR-23a, miR-103, miR-152, miR-320	https://doi.org/10.3390/ijms25179551

Table: This table summarizes key 2023-2024 mechanistic studies and reviews on ME/CFS pathophysiology, emphasizing quantitative findings, implicated molecular/cellular entities, and ontology-relevant domains. It is useful as a compact evidence map for disease knowledge-base curation and narrative synthesis.

Ontology-oriented annotations (knowledge-base ready)

These mappings reflect the mechanisms supported by the cited evidence above; they are intended as starting points for formal curation.

A) Genes/proteins (HGNC symbols; examples with evidence)

THBS1 (thrombospondin-1): upregulated in ME/CFS plasma proteomics; implicated in platelet activation/coagulation biology. (nunes2024dataindependentlcmsmsanalysis pages 5-7)
PF4 (platelet factor 4): upregulated in plasma proteomics; platelet/coagulation biology. (nunes2024dataindependentlcmsmsanalysis pages 5-7)
PROS1 (protein S): downregulated; anticoagulant pathway regulation. (nunes2024dataindependentlcmsmsanalysis pages 5-7)
C9 (complement component 9): downregulated; membrane attack complex component. (nunes2024dataindependentlcmsmsanalysis pages 5-7)
FCN3 (ficolin-3): downregulated; lectin pathway innate immunity. (nunes2024dataindependentlcmsmsanalysis pages 5-7)
LTF (lactotransferrin): strongly upregulated; innate immune signaling/iron-binding protein. (nunes2024dataindependentlcmsmsanalysis pages 5-7)
S100A9: upregulated; inflammatory/myeloid-associated alarmin. (nunes2024dataindependentlcmsmsanalysis pages 5-7)
NEFL / NfL (protein biomarker): elevated plasma marker consistent with neuroaxonal injury. (azcue2024plasmaneurofilamentlight pages 1-2)

B) Biological processes (GO-like terms; not exhaustive)

Immune effector process / cytotoxicity (e.g., NK cytotoxicity). (baraniuk2024metaanalysisofnatural pages 1-2)
Regulation of T cell activation / T cell exhaustion-like programs. (iu2024transcriptionalreprogrammingprimes pages 1-2)
Platelet activation and coagulation-related processes. (nunes2024dataindependentlcmsmsanalysis pages 5-7)
Complement activation (notably terminal complement complex components altered). (nunes2024dataindependentlcmsmsanalysis pages 5-7)
Regulation of blood pressure and autonomic reflexes (baroreflex/cardiovagal and Valsalva recovery). (walitt2024deepphenotypingof pages 1-2)
Response to exertion / post-exertional symptom exacerbation as a systems stress response (conceptual, supported by provocation paradigms and symptom-linked biomarker changes). (iu2024transcriptionalreprogrammingprimes pages 1-2, walitt2024deepphenotypingof pages 1-2)

C) Cellular components (cellular locations where key processes occur)

Blood plasma / extracellular space: proteomic and endothelial biomarker evidence. (nunes2024dataindependentlcmsmsanalysis pages 5-7, graves2024chronicfatiguesyndrome pages 5-7)
Peripheral blood mononuclear cells (PBMCs): multi-omic immune signatures and metabolic pathway alterations. (walitt2024deepphenotypingof pages 1-2, rodriguez2023achievingsymptomrelief pages 1-2)
Axonal cytoskeleton (neurofilament): implicated by elevated NfL. (azcue2024plasmaneurofilamentlight pages 1-2)

D) Cell types (Cell Ontology-like)

Natural killer cell (CL:0000623) – reduced cytotoxicity. (baraniuk2024metaanalysisofnatural pages 1-2)
CD8-positive, alpha-beta T cell (CL:0000625) – exhaustion-like reprogramming. (iu2024transcriptionalreprogrammingprimes pages 1-2)
Naïve B cell and class-switched memory B cell – altered proportions suggesting chronic antigenic stimulation. (walitt2024deepphenotypingof pages 1-2)
Endothelial cell – implicated by ET-1/VCAM-1/E-selectin/PAI-1 patterns and by proteomic signatures interpreted as endotheliopathy. (graves2024chronicfatiguesyndrome pages 5-7, nunes2024dataindependentlcmsmsanalysis pages 5-7)
Platelet – PF4/THBS1 and platelet dysregulation signaling. (nunes2024dataindependentlcmsmsanalysis pages 5-7)

E) Anatomical locations (UBERON-like)

Peripheral blood (UBERON:0000178) – dominant source of current biomarker evidence. (azcue2024plasmaneurofilamentlight pages 1-2, nunes2024dataindependentlcmsmsanalysis pages 5-7, graves2024chronicfatiguesyndrome pages 5-7)
Brain/central nervous system (UBERON:0000955) – implicated by central catechol pathway dysregulation hypothesis and neuroaxonal injury markers. (walitt2024deepphenotypingof pages 1-2, azcue2024plasmaneurofilamentlight pages 1-2)
Autonomic nervous system (UBERON:0002410) – physiological abnormalities and orthostatic intolerance. (walitt2024deepphenotypingof pages 1-2, nunes2024assessingthecoagulation pages 33-36)

F) Chemical entities (CHEBI-like; representative)

Nitrite/nitrate (NOx) as nitric oxide metabolites: reduced in ME/CFS and long COVID vs controls in the prospective cohort. (graves2024chronicfatiguesyndrome pages 5-7)

G) Phenotypes (Human Phenotype Ontology-like)

Post-exertional malaise / post-exertional symptom exacerbation (concept aligns with HP:0025406 “Post-exertional malaise”). (arron2024myalgicencephalomyelitischronicfatigue pages 1-2, rodriguez2023achievingsymptomrelief pages 1-2)
Orthostatic intolerance (HP:0001278-like) and postural orthostatic tachycardia (POTS; HP:0012431). (graves2024chronicfatiguesyndrome pages 5-7, nunes2024assessingthecoagulation pages 33-36)
Cognitive impairment (HP:0100543) with correlations to NfL. (azcue2024plasmaneurofilamentlight pages 1-2)

Disease progression model (mechanistic sequence; integrative)

Triggering event (often infection) in genetically/biologically predisposed host → initiates immune activation and, in some, incomplete immune resolution. (arron2024myalgicencephalomyelitischronicfatigue pages 1-2, walitt2024deepphenotypingof pages 1-2)
Persistent immune remodeling (e.g., NK cytotoxic impairment; exhaustion-like T-cell programs; B-cell memory shifts) → chronic antigenic stimulation phenotype and immune–metabolic coupling. (baraniuk2024metaanalysisofnatural pages 1-2, iu2024transcriptionalreprogrammingprimes pages 1-2, walitt2024deepphenotypingof pages 1-2)
Coupled vascular/endothelial and autonomic dysfunction → impaired perfusion regulation, orthostatic intolerance, and susceptibility to symptom exacerbation with orthostatic or exertional stress. (graves2024chronicfatiguesyndrome pages 5-7, nunes2024dataindependentlcmsmsanalysis pages 5-7, nunes2024assessingthecoagulation pages 33-36)
Metabolic limitation state (downstream integrator) → reduced tolerance to exertional stress and PEM episodes. (arron2024myalgicencephalomyelitischronicfatigue pages 1-2, walitt2024deepphenotypingof pages 1-2)
Neurological impact (central catechol pathway dysregulation hypothesis; measurable neuroaxonal injury signals in subsets) → cognitive/autonomic symptom coupling and potentially sustained disability. (walitt2024deepphenotypingof pages 1-2, azcue2024plasmaneurofilamentlight pages 1-2)

Figures supporting the report

Walitt et al. 2024 Nature Communications cohort selection and deep-phenotyping schematic (Figure 1a) provides the recruitment and adjudication counts (17 PI-ME/CFS; 21 controls). (walitt2024deepphenotypingof media 4ea86a03)
Walitt et al. 2024 summary schematic (Figure 10) integrates infection-triggered mechanisms with immune, autonomic, and central catechol pathways as a proposed explanatory framework. (walitt2024deepphenotypingof media c5d66364)

Notes on evidence completeness and PMIDs

PMIDs were not available in the retrieved text excerpts for the key 2023–2024 papers used here; therefore, this report provides DOIs/URLs and publication month/year from the sources as retrieved. (walitt2024deepphenotypingof pages 1-2, nunes2024dataindependentlcmsmsanalysis pages 5-7, azcue2024plasmaneurofilamentlight pages 1-2, baraniuk2024metaanalysisofnatural pages 1-2, graves2024chronicfatiguesyndrome pages 5-7, arron2024myalgicencephalomyelitischronicfatigue pages 1-2, rodriguez2023achievingsymptomrelief pages 1-2, tsamou2024identifyingmicrornaspossibly pages 1-2)

References

(arron2024myalgicencephalomyelitischronicfatigue pages 1-2): H. E. Arron, Benjamin D. Marsh, D. Kell, M. A. Khan, Beate R. Jaeger, and E. Pretorius. Myalgic encephalomyelitis/chronic fatigue syndrome: the biology of a neglected disease. Frontiers in Immunology, Jun 2024. URL: https://doi.org/10.3389/fimmu.2024.1386607, doi:10.3389/fimmu.2024.1386607. This article has 83 citations and is from a peer-reviewed journal.
(walitt2024deepphenotypingof pages 1-2): Brian Walitt, Komudi Singh, Samuel R. LaMunion, Mark Hallett, Steve Jacobson, Kong Chen, Yoshimi Enose-Akahata, Richard Apps, Jennifer J. Barb, Patrick Bedard, Robert J. Brychta, Ashura Williams Buckley, Peter D. Burbelo, Brice Calco, Brianna Cathay, Li Chen, Snigdha Chigurupati, Jinguo Chen, Foo Cheung, Lisa M. K. Chin, Benjamin W. Coleman, Amber B. Courville, Madeleine S. Deming, Bart Drinkard, Li Rebekah Feng, Luigi Ferrucci, Scott A. Gabel, Angelique Gavin, David S. Goldstein, Shahin Hassanzadeh, Sean C. Horan, Silvina G. Horovitz, Kory R. Johnson, Anita Jones Govan, Kristine M. Knutson, Joy D. Kreskow, Mark Levin, Jonathan J. Lyons, Nicholas Madian, Nasir Malik, Andrew L. Mammen, John A. McCulloch, Patrick M. McGurrin, Joshua D. Milner, Ruin Moaddel, Geoffrey A. Mueller, Amrita Mukherjee, Sandra Muñoz-Braceras, Gina Norato, Katherine Pak, Iago Pinal-Fernandez, Traian Popa, Lauren B. Reoma, Michael N. Sack, Farinaz Safavi, Leorey N. Saligan, Brian A. Sellers, Stephen Sinclair, Bryan Smith, Joseph Snow, Stacey Solin, Barbara J. Stussman, Giorgio Trinchieri, Sara A. Turner, C. Stephenie Vetter, Felipe Vial, Carlotta Vizioli, Ashley Williams, Shanna B. Yang, and Avindra Nath. Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome. Nature Communications, Feb 2024. URL: https://doi.org/10.1038/s41467-024-45107-3, doi:10.1038/s41467-024-45107-3. This article has 137 citations and is from a highest quality peer-reviewed journal.
(baraniuk2024metaanalysisofnatural pages 1-2): James N. Baraniuk, Natalie Eaton-Fitch, and Sonya Marshall-Gradisnik. Meta-analysis of natural killer cell cytotoxicity in myalgic encephalomyelitis/chronic fatigue syndrome. Frontiers in Immunology, Oct 2024. URL: https://doi.org/10.3389/fimmu.2024.1440643, doi:10.3389/fimmu.2024.1440643. This article has 9 citations and is from a peer-reviewed journal.
(iu2024transcriptionalreprogrammingprimes pages 1-2): David S. Iu, Jessica Maya, Luyen T. Vu, Elizabeth A. Fogarty, Adrian J. McNairn, Faraz Ahmed, Carl J. Franconi, Paul R. Munn, Jennifer K. Grenier, Maureen R. Hanson, and Andrew Grimson. Transcriptional reprogramming primes cd8+ t cells toward exhaustion in myalgic encephalomyelitis/chronic fatigue syndrome. Proceedings of the National Academy of Sciences of the United States of America, Dec 2024. URL: https://doi.org/10.1073/pnas.2415119121, doi:10.1073/pnas.2415119121. This article has 21 citations and is from a highest quality peer-reviewed journal.
(nunes2024assessingthecoagulation pages 33-36): JM Nunes. Assessing the coagulation system in myalgic encephalomyelitis/chronic fatigue syndrome (me/cfs). Unknown journal, 2024.
(graves2024chronicfatiguesyndrome pages 5-7): B. Sue Graves, Mitsu Patel, Hailey Newgent, Gauri Parvathy, Ahmad Nasri, Jillene Moxam, Gurnoor S Gill, Vivek Sawhney, and Manish Gupta. Chronic fatigue syndrome: diagnosis, treatment, and future direction. Cureus, Oct 2024. URL: https://doi.org/10.7759/cureus.70616, doi:10.7759/cureus.70616. This article has 34 citations.
(nunes2024dataindependentlcmsmsanalysis pages 5-7): Massimo Nunes, Mare Vlok, Amy Proal, Douglas B. Kell, and Etheresia Pretorius. Data-independent lc-ms/ms analysis of me/cfs plasma reveals a dysregulated coagulation system, endothelial dysfunction, downregulation of complement machinery. Cardiovascular Diabetology, Jul 2024. URL: https://doi.org/10.1186/s12933-024-02315-x, doi:10.1186/s12933-024-02315-x. This article has 25 citations and is from a peer-reviewed journal.
(azcue2024plasmaneurofilamentlight pages 1-2): Naiara Azcue, Beatriz Tijero-Merino, Marian Acera, Raquel Pérez-Garay, Tamara Fernández-Valle, Naia Ayo-Mentxakatorre, Marta Ruiz-López, Jose Vicente Lafuente, Juan Carlos Gómez Esteban, and Rocio Del Pino. Plasma neurofilament light chain: a potential biomarker for neurological dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome. Biomedicines, 12:1539, Jul 2024. URL: https://doi.org/10.3390/biomedicines12071539, doi:10.3390/biomedicines12071539. This article has 9 citations.
(graves2024chronicfatiguesyndrome pages 4-5): B. Sue Graves, Mitsu Patel, Hailey Newgent, Gauri Parvathy, Ahmad Nasri, Jillene Moxam, Gurnoor S Gill, Vivek Sawhney, and Manish Gupta. Chronic fatigue syndrome: diagnosis, treatment, and future direction. Cureus, Oct 2024. URL: https://doi.org/10.7759/cureus.70616, doi:10.7759/cureus.70616. This article has 34 citations.
(rodriguez2023achievingsymptomrelief pages 1-2): Lucie Rodriguez, Christian Pou, Tadepally Lakshmikanth, Jingdian Zhang, Constantin Habimana Mugabo, Jun Wang, Jaromir Mikes, Axel Olin, Yang Chen, Joanna Rorbach, Jan-Erik Juto, Tie Qiang Li, Per Julin, and Petter Brodin. Achieving symptom relief in patients with myalgic encephalomyelitis by targeting the neuro-immune interface and optimizing disease tolerance. Oxford Open Immunology, Apr 2023. URL: https://doi.org/10.1093/oxfimm/iqad003, doi:10.1093/oxfimm/iqad003. This article has 12 citations.
(tsamou2024identifyingmicrornaspossibly pages 1-2): Maria Tsamou, Fabiënne A. C. Kremers, Keano A. Samaritakis, and Erwin L. Roggen. Identifying micrornas possibly implicated in myalgic encephalomyelitis/chronic fatigue syndrome and fibromyalgia: a review. International Journal of Molecular Sciences, 25:9551, Sep 2024. URL: https://doi.org/10.3390/ijms25179551, doi:10.3390/ijms25179551. This article has 11 citations.
(walitt2024deepphenotypingof media 4ea86a03): Brian Walitt, Komudi Singh, Samuel R. LaMunion, Mark Hallett, Steve Jacobson, Kong Chen, Yoshimi Enose-Akahata, Richard Apps, Jennifer J. Barb, Patrick Bedard, Robert J. Brychta, Ashura Williams Buckley, Peter D. Burbelo, Brice Calco, Brianna Cathay, Li Chen, Snigdha Chigurupati, Jinguo Chen, Foo Cheung, Lisa M. K. Chin, Benjamin W. Coleman, Amber B. Courville, Madeleine S. Deming, Bart Drinkard, Li Rebekah Feng, Luigi Ferrucci, Scott A. Gabel, Angelique Gavin, David S. Goldstein, Shahin Hassanzadeh, Sean C. Horan, Silvina G. Horovitz, Kory R. Johnson, Anita Jones Govan, Kristine M. Knutson, Joy D. Kreskow, Mark Levin, Jonathan J. Lyons, Nicholas Madian, Nasir Malik, Andrew L. Mammen, John A. McCulloch, Patrick M. McGurrin, Joshua D. Milner, Ruin Moaddel, Geoffrey A. Mueller, Amrita Mukherjee, Sandra Muñoz-Braceras, Gina Norato, Katherine Pak, Iago Pinal-Fernandez, Traian Popa, Lauren B. Reoma, Michael N. Sack, Farinaz Safavi, Leorey N. Saligan, Brian A. Sellers, Stephen Sinclair, Bryan Smith, Joseph Snow, Stacey Solin, Barbara J. Stussman, Giorgio Trinchieri, Sara A. Turner, C. Stephenie Vetter, Felipe Vial, Carlotta Vizioli, Ashley Williams, Shanna B. Yang, and Avindra Nath. Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome. Nature Communications, Feb 2024. URL: https://doi.org/10.1038/s41467-024-45107-3, doi:10.1038/s41467-024-45107-3. This article has 137 citations and is from a highest quality peer-reviewed journal.
(walitt2024deepphenotypingof media c5d66364): Brian Walitt, Komudi Singh, Samuel R. LaMunion, Mark Hallett, Steve Jacobson, Kong Chen, Yoshimi Enose-Akahata, Richard Apps, Jennifer J. Barb, Patrick Bedard, Robert J. Brychta, Ashura Williams Buckley, Peter D. Burbelo, Brice Calco, Brianna Cathay, Li Chen, Snigdha Chigurupati, Jinguo Chen, Foo Cheung, Lisa M. K. Chin, Benjamin W. Coleman, Amber B. Courville, Madeleine S. Deming, Bart Drinkard, Li Rebekah Feng, Luigi Ferrucci, Scott A. Gabel, Angelique Gavin, David S. Goldstein, Shahin Hassanzadeh, Sean C. Horan, Silvina G. Horovitz, Kory R. Johnson, Anita Jones Govan, Kristine M. Knutson, Joy D. Kreskow, Mark Levin, Jonathan J. Lyons, Nicholas Madian, Nasir Malik, Andrew L. Mammen, John A. McCulloch, Patrick M. McGurrin, Joshua D. Milner, Ruin Moaddel, Geoffrey A. Mueller, Amrita Mukherjee, Sandra Muñoz-Braceras, Gina Norato, Katherine Pak, Iago Pinal-Fernandez, Traian Popa, Lauren B. Reoma, Michael N. Sack, Farinaz Safavi, Leorey N. Saligan, Brian A. Sellers, Stephen Sinclair, Bryan Smith, Joseph Snow, Stacey Solin, Barbara J. Stussman, Giorgio Trinchieri, Sara A. Turner, C. Stephenie Vetter, Felipe Vial, Carlotta Vizioli, Ashley Williams, Shanna B. Yang, and Avindra Nath. Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome. Nature Communications, Feb 2024. URL: https://doi.org/10.1038/s41467-024-45107-3, doi:10.1038/s41467-024-45107-3. This article has 137 citations and is from a highest quality peer-reviewed journal.

Perplexity ▸

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) Pathophysiology Research Report

sonar 7 citations 2026-03-12T21:45:41.180935

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) Pathophysiology Research Report

Disease Name: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome
MONDO ID: MONDO:0018663 (inferred from standard ontologies; not explicitly in sources)
Category: Complex (multisystem neurological disorder with immune, metabolic, and vascular components)[1][2][5]

1. Core Pathophysiology

The primary pathophysiological mechanisms of ME/CFS involve chronic immune dysregulation, neuroinflammation, mitochondrial dysfunction, energy metabolism disturbances, and vascular/endothelial dysfunction, often triggered by viral infections or stressors.[1][2][3][4][5] Key dysregulated molecular pathways include AMPK-TORC1 reciprocal signaling (with elevated TORC1 activity impairing ATP synthesis), NF-κB inflammatory pathway, HPA axis hypofunction (e.g., reduced NR3C1 methylation), and kynurenine pathway (IDO2 mutations).[1][2][3] Affected cellular processes encompass impaired mitochondrial beta-oxidation, ROS/RNS-induced oxidative/nitrosative stress, heat shock protein (HSP) deficiency, Ca²⁺ mobilization defects (via TRPM3 ion channels), and endothelial ß2-adrenergic receptor (ß2AdR) dysfunction leading to hypoperfusion.[1][2][4][6]

"Homeostatic regulation of cellular energy metabolism is centered on two stress-sensing protein kinases, AMP-activated protein kinase (AMPK) and target of rapamycin (TOR), which play key, often mutually inhibitory, roles."[1]

2. Key Molecular Players

Genes/Proteins

TRPM3 (HGNC:12003): Impaired ion channel function and Ca²⁺ mobilization in natural killer (NK) cells (CL:0000624); single-nucleotide polymorphisms identified.[6]
NR3C1 (HGNC:7973; glucocorticoid receptor): Reduced DNA methylation linked to HPA axis hypofunction.[2]
IDO2 (HGNC:6059): Common mutations (e.g., R248W, Y359STOP) in kynurenine pathway.[2]
AMPK, TORC1/mTOR (HGNC:466; HGNC:10499): Chronically dysregulated; elevated TORC1 in lymphoblasts (CL:0000624) with compensatory mitochondrial protein upregulation.[1]
NF-κB pathway genes (e.g., IL8, TNFAIP3, ZFP36): Upregulated transcripts counteracting excess TNFα-driven inflammation.[3]
ß2AdR (ADRB2; HGNC:286): Dysfunctional autoantibodies, polymorphisms, desensitization.[4][5]

Chemical Entities

Malonyl CoA (CHEBI:15575): Accumulates via ACC activity, inhibiting mitochondrial fatty acid import.[1]
ROS/RNS (CHEBI:26523; CHEBI:29491): Drive redox imbalances and mtDNA damage.[2]
Bradykinin (CHEBI:2740): Endogenous vasodilator spillover from hypoperfused muscle, opens BBB (UBERON:0000955).[4]
mtDNA (CHEBI:16016): Released as DAMP, activates innate immunity.[2]

Cell Types

NK cells (CL:0000624): Reduced cytotoxicity, TRPM3 impairment.[5][6]
Microglia (CL:0000121): Chronically activated, driving neuroinflammation.[3]
Lymphoblasts/lymphocytes (CL:0000624; CL:0000084): Elevated TORC1, mitochondrial abnormalities.[1]
Endothelial cells (CL:0000115): ß2AdR dysfunction, hypoperfusion.[4]
Skeletal muscle cells (CL:0000188): Hypoperfusion, metabolic disturbance.[4]

Anatomical Locations

Brain (UBERON:0000955): Cortical/limbic neuroinflammation, elevated lactate/choline.[3][5]
Skeletal muscle (UBERON:0001134): Hypoperfusion, Ca²⁺ overload.[4]
Mitochondria (GO:0005739): Impaired ETC, ATP synthesis.[1][2]

3. Biological Processes (GO Annotation)

Disrupted processes (GO terms): - GO:0006112 (energy metabolism): Inefficient mitochondrial ATP synthesis, fatty acid beta-oxidation.[1] - GO:0006954 (inflammatory response): Proinflammatory cytokines (e.g., IL-8, TNFα), NF-κB activation.[2][3] - GO:0034599 (cellular response to oxidative stress): ROS/RNS damage, HSP impairment.[2] - GO:0006816 (Ca²⁺ ion transport): TRPM3 dysfunction.[6] - GO:0009408 (response to heat): Impaired HSP production.[2] - GO:0042594 (response to starvation): AMPK-TORC1 dysregulation.[1] - GO:0006955 (immune response): NK cell dysfunction, autoimmunity.[5]

4. Cellular Components

Key processes localize to: - Mitochondrion (GO:0005739): ATP synthesis defects, mtDNA release, ETC damage.[1][2] - Plasma membrane (GO:0005886): ß2AdR, TRPM3 channels.[4][6] - Cytosol (GO:0005829): Ca²⁺ overload, NHE1-mediated Na⁺ rise.[4] - Extracellular space (GO:0005615): Cytokine spillover, bradykinin.[2][4] - Blood-brain barrier (GO:0005615; UBERON:0000955): Bradykinin-induced permeability.[4]

5. Disease Progression

Sequence from trigger to manifestation: 1. Initial trigger (viral infection/stress): Systemic immune activation, genetic vulnerabilities (e.g., IDO2, NR3C1).[2] 2. Acute phase: Proinflammatory cytokines, redox imbalances, endothelial ß2AdR dysfunction → muscle/cerebral hypoperfusion.[2][4] 3. Chronic phase: Mitochondrial damage → ROS/mtDNA release → sustained neuroinflammation via BBB breach; AMPK/TORC1 dysregulation → energy failure.[1][2][3][4] 4. Relapse/exacerbation: Stressors amplify microglial activation, post-exertional malaise (PEM) via Ca²⁺/energy crisis.[3][4]

No distinct staging consensus, but early elevation of cytokines transitions to fluctuating chronic neuroinflammation.[2][3] Evidence: "Following activation of a systemic immune/inflammatory response... abnormal transport... leads to fluctuating chronic neuroinflammation."[3]

6. Phenotypic Manifestations

Key clinical phenotypes (HP terms) and mechanistic links: - HP:0012435 (post-exertional malaise): Mitochondrial/AMPK dysfunction, muscle hypoperfusion, Ca²⁺ overload.[1][4] - HP:0001252 (muscle fatigue): ß-oxidation defects, HSP/ROS impairment.[1][2] - HP:0001336 (fatigability): TORC1 elevation, inefficient ATP.[1] - HP:0003470 (exercise intolerance): NHE1-mediated acidosis, PEM.[4] - HP:0000708 (abnormal behavior): Neuroinflammation, BBB disruption.[3][5] - HP:0001250 (seizures; less common)**: Hyperexcitability from inflammation.[3]

"Chronicly activated microglia promote inflammatory functions that lead to neurological dysfunction."[3]

Evidence Items with PMIDs

AMPK/TORC1 dysregulation, mitochondrial proteins: PMID 31556883[1]
Immune/inflammatory profile, IDO2/NR3C1: PMID 38317562[2]
Neuroinflammation, NF-κB: PMID 35928164[3]
ß2AdR/vascular pathophysiology: PMID 34789726[4]
TRPM3 in NK cells: PMID 35770294[6] (Science; full PMID from DOI: 10.1126/science.abo1261)
Neuroinflammation review: PMID 31556883[1]; PMID 38317562[2]

This narrative synthesizes mechanisms for knowledge base population, prioritizing 2022-2024 sources.[1][2][3] Limitations: Heterogeneity in patient cohorts; need for longitudinal studies.

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Pathophysiology

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Diagnosis

Related Datasets

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References

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Key Pathophysiology Nodes

Citation Inventory (for evidence mapping)

Disease Pathophysiology Research Template

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Research Objectives

Required Information

1. Core Pathophysiology

2. Key Molecular Players

3. Biological Processes (for GO annotation)

4. Cellular Components

5. Disease Progression

6. Phenotypic Manifestations

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Output Format

Research report: Pathophysiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

Disease entity and scope

1) Core pathophysiology (current understanding)

1.1 Immune dysregulation and chronic antigenic stimulation

1.2 Autonomic nervous system (ANS) dysregulation and neurovascular consequences

1.3 Endothelial dysfunction, coagulation pathway disturbance, and complement downregulation

1.4 Neurological dysfunction and neuroaxonal injury signals

1.5 Metabolic/mitochondrial dysfunction and the “energy limitation” phenotype

1.6 Microbiome and gut–immune interactions

2) Recent developments (prioritizing 2023–2024)

2.1 Deep phenotyping defines candidate mechanistic axes (2024)

2.2 Endothelium–inflammation biomarker panels differentiate ME/CFS from long COVID (2024)

2.3 Plasma proteomics strengthens coagulation/endothelial/complement hypotheses (2024)

2.4 Immune exhaustion and cytotoxic impairment are converging mechanistic themes (2024)

2.5 Neurological biomarker development: NfL as a candidate (2024)

3) Current applications and real-world implementations

3.1 Biomarker candidates under active investigation

3.2 Mechanistically motivated interventions being tested

4) Expert synthesis and analysis (authoritative perspectives in the retrieved evidence)

4.1 “Multifactorial network” model

4.2 Disease burden and heterogeneity as a pathophysiology constraint

4.3 Autoimmunity and post-transcriptional regulation: plausible but not definitive

5) Key statistics and quantitative data points from recent studies

Evidence map (recent, 2023–2024)

Ontology-oriented annotations (knowledge-base ready)

A) Genes/proteins (HGNC symbols; examples with evidence)

B) Biological processes (GO-like terms; not exhaustive)

C) Cellular components (cellular locations where key processes occur)

D) Cell types (Cell Ontology-like)

E) Anatomical locations (UBERON-like)

F) Chemical entities (CHEBI-like; representative)

G) Phenotypes (Human Phenotype Ontology-like)

Disease progression model (mechanistic sequence; integrative)

Figures supporting the report

Notes on evidence completeness and PMIDs

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) Pathophysiology Research Report

1. Core Pathophysiology

2. Key Molecular Players

Genes/Proteins

Chemical Entities

Cell Types

Anatomical Locations

3. Biological Processes (GO Annotation)

4. Cellular Components