Pathomechanisms and possible interventions in myalgic encephalomyelitis/ chronic fatigue syndrome (ME/CFS), by Øystein Fluge, Karl J. Tronstad, and Olav Mella in J Clin Invest. 2021;131(14):e150377 [doi.org/10.1172/JCI150377] July 15, 2021
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disease with unknown etiology, no validated specific and sensitive biomarker, and no standard approved effective treatment. ME/CFS has a profound impact on the quality of life of both patients and caregivers and entails high costs for society. The severity varies among patients who are able to participate to some extent in social life (mild), those who are mainly housebound (moderate) or bedridden (severe), and the very severely ill who are completely dependent on assistance for all daily living tasks, such as feeding or turning around in bed.
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) often starts in previously healthy individuals after an infection, the most common being infectious mononucleosis (EBV). It is more frequent in women and influenced by genetic predisposition. The main symptoms are postexertional malaise (PEM), fatigue, orthostatic intolerance, cognitive disturbances, sleep problems with inadequate restitution after rest, sensory hypersensitivity with pain, and symptoms related to autonomic and immune dysfunction. The prevalence is 0.1% to 0.8%, and ME/CFS must be distinguished from general fatigue, which is much more common in the population.
Historically, there has been limited scientific interest in ME/CFS.
Herein, we suggest a framework model for the initiation and maintenance of ME/CFS consisting of three principal steps:
(a) an initial aberrant immune response;
(b) an effector system for symptom generation and maintenance; and
(c) compensatory adaptations.
The model and possible therapeutic opportunities are summarized in Figure 1.
Our proposed pathomechanistic model is compatible with the lack of obvious histologic inflammation in tissue samples from ME/CFS, lack of overt organ damage, and the potential for recovery — sometimes spontaneous and without sequelae. Future research should focus on the natural course of ME/CFS over time to identify the mechanisms that induce and maintain disease, find targets for intervention, and specifically aim to elucidate immune dysregulation and patterns of autoantibodies with mechanisms for circulatory disturbances.
In our model, clinical symptoms of ME/CFS are related primarily to the inadequate autoregulation of blood flow yielding tissue hypoxia on exertion, but are also influenced by the compensatory adaptations from increased sympathetic output and from metabolic shifts.
We speculate that cognitive techniques, which are reported to help subgroups of patients, might act by modulating the sympathetic output. If so, one would expect a greater benefit for patients with less ongoing immune activation and less vascular dysregulation, but with main symptom contributions from the secondary autonomic adaptations. Conversely, patients with active immune disturbance and ongoing vascular dysregulation as the main symptom generators would have less impact from cognitive intervention, although psychosocial support and coping strategies may still have a beneficial impact on their quality of life.
In conclusion, we suggest that ME/CFS in a subgroup of patients is a variant of an autoimmune disease, with a role for B cells/plasma cells and a pattern of autoantibodies emerging after infection and persisting over time. Key symptoms may result from the consequent functional disturbance in blood flow autoregulation causing tissue hypoxia on exertion and associated autonomic and metabolic responses to maintain energy homeostasis.
Finally, there is growing concern for patients with “long COVID.” Research is needed to determine whether the symptoms, which may resemble those of ME/CFS, are caused by subtle organ damage from the viral infection or whether subgroups of “long haulers” actually have a postinfectious immune disturbance and pathomechanism similar to those in ME/CFS.
News-medical.net: Researchers unravel pathomechanisms involved in Chronic Fatigue Syndrome, by Emily Henderson 23 Aug 2021
Medical xpress: Myalgic encephalomyelitis associated with cellular energy strain Aug 23 2021
biochemical changes in the blood of ME patients support the hypothesis that the disease involves impaired cellular energy metabolism.
See also: Research: A map of metabolic phenotypes in patients with ME/CFS