Etiology, pathology, genomics, physiology, and clinical cours
Abstract
Autonomic dysfunction has emerged as one of the most reproducible physiological phenotypes of Long COVID, encompassing postural orthostatic tachycardia syndrome (POTS), orthostatic intolerance, inappropriate sinus tachycardia, orthostatic hypotension, altered vasomotor control, sudomotor abnormalities and gastrointestinal, urinary and thermoregulatory dysfunction. The phenotype is clinically important because it can unite otherwise apparently disparate manifestations—tachycardia, dizziness, presyncope, fatigue, cognitive dysfunction, exercise intolerance, dyspnoea, gastrointestinal dysmotility and post-exertional malaise—within a coherent physiological framework. Quantitative autonomic testing has now demonstrated measurable abnormalities in patients with Long COVID, although the severity and pattern vary considerably among individuals.[1]
The pathogenesis is almost certainly heterogeneous. Proposed mechanisms include immune-mediated injury to autonomic pathways, functional autoantibodies against G-protein-coupled receptors, small-fiber neuropathy, impaired sympathetic vasoconstriction, reduced circulating blood volume, venous pooling, endothelial dysfunction, abnormal cerebral blood-flow regulation, hyperadrenergic activation, mast-cell and inflammatory signaling, altered respiratory physiology and persistent viral or antigenic stimulation. Increasing pathological evidence supports autonomic small-fiber involvement: recent skin-biopsy studies demonstrate reduced autonomic nerve-fiber density in sweat glands and piloerector muscles in patients with painful Long COVID, in some cases despite preserved somatic intraepidermal nerve-fiber density.[2]
A particularly compelling mechanistic hypothesis involves functional autoantibodies against adrenergic, muscarinic and vasoactive G-protein-coupled receptors. Studies have identified such antibodies in substantial proportions of patients with Long COVID and have associated specific receptor profiles with POTS, dizziness, cognitive dysfunction, fatigue and post-exertional malaise.[3–5] More recent work combining autoantibody analysis with adaptive immune-receptor sequencing suggests that autonomic Long COVID may contain an immunogenetically identifiable phenotype, although causality remains unproven.[6] Host genetics probably contributes through variation in immune regulation, vascular signaling, adrenergic responsiveness and autonomic susceptibility, but no validated genetic test currently identifies individuals at risk.
The clinical course is variable. Some patients develop orthostatic intolerance within weeks of infection and gradually improve; others develop chronic POTS or a broader dysautonomia persisting for years. Autonomic dysfunction may coexist with small-fiber neuropathy, ME/CFS-like post-exertional malaise, cerebral hypoperfusion and metabolic dysfunction. The therapeutic implications are substantial. Diagnosis requires physiological testing rather than symptom attribution alone; treatment generally begins with volume and venous-return strategies, compression, carefully individualised physical reconditioning when tolerated, and pharmacological modulation of heart rate, vascular tone or volume. The evidence base for immunotherapy remains preliminary. The emerging literature supports a model in which Long-COVID dysautonomia represents not a single autonomic disease but a family of postinfectious neurovascular and neuroimmune disorders.
Introduction
The autonomic nervous system is the physiological interface between the organism and its internal environment.
It continuously regulates:
- heart rate;
- arterial pressure;
- vascular resistance;
- venous return;
- respiration;
- thermoregulation;
- gastrointestinal motility;
- bladder function;
- sweating;
- pupillary responses;
- endocrine-metabolic adaptation.
The autonomic system therefore operates largely outside conscious control, yet its failure can produce symptoms throughout virtually every organ system.
This characteristic makes dysautonomia particularly relevant to Long COVID.
A patient may present with:
- palpitations;
- dizziness;
- exertional intolerance;
- fatigue;
- brain fog;
- nausea;
- abdominal discomfort;
- sweating abnormalities;
- temperature dysregulation;
- urinary symptoms;
- headache;
- presyncope or syncope.
These manifestations may initially appear unrelated.
They are not necessarily unrelated.
The common denominator may be failure of the physiological mechanisms that maintain cardiovascular and visceral homeostasis.
Autonomic dysfunction was recognised early in the pandemic as a possible explanation for persistent palpitations and orthostatic symptoms after SARS-CoV-2 infection.[7] Subsequent studies have transformed this from a plausible clinical observation into a measurable physiological phenotype.
A 2023 prospective study of patients with post-acute sequelae of SARS-CoV-2 infection (PASC) found substantial autonomic abnormalities, including impaired respiratory sinus arrhythmia and exaggerated heart-rate responses during standing; most participants in the PASC group met established criteria for POTS.[8]
More recent quantitative testing has provided additional evidence that autonomic abnormalities in Long COVID are not simply subjective manifestations of fatigue or anxiety.[1]
The question has therefore shifted from:
Does Long COVID cause dysautonomia?
to:
What biological process produces autonomic failure after SARS-CoV-2 infection, and why does it persist?
I. The Autonomic Nervous System as a Homeostatic Control Network
The autonomic nervous system consists principally of:
- sympathetic pathways;
- parasympathetic pathways;
- enteric neural networks.
Its cardiovascular functions are particularly relevant to Long COVID.
Upon standing, approximately 500–800 mL of blood can transiently redistribute toward the lower extremities and abdomen.
The normal response is rapid:
standing
→ venous pooling
→ reduced venous return
→ reduced stroke volume
→ baroreceptor activation
→ sympathetic activation
→ increased heart rate and vascular resistance
→ restoration of cerebral perfusion.
This process is the baroreflex.
Failure at any point can produce orthostatic intolerance.
II. Orthostatic Intolerance
Orthostatic intolerance (OI) describes symptoms provoked or worsened by upright posture and relieved by recumbency.
Symptoms may include:
- light-headedness;
- dizziness;
- blurred vision;
- weakness;
- palpitations;
- cognitive impairment;
- nausea;
- dyspnoea;
- presyncope;
- fatigue.
POTS is one specific form.
In adults, POTS is generally defined by a sustained heart-rate increase of at least 30 beats per minute within 10 minutes of standing or head-up tilt, without classical orthostatic hypotension and with compatible chronic symptoms.
POTS is not synonymous with Long COVID.
Rather, it is one physiological phenotype that can occur following SARS-CoV-2 infection.
III. The Emergence of POTS as a Long-COVID Phenotype
The association between SARS-CoV-2 infection and POTS became increasingly apparent during the first years of the pandemic.
Population-level analyses subsequently provided epidemiological support.
Kwan and colleagues reported that individuals following SARS-CoV-2 infection had substantially increased rates of POTS-associated diagnoses compared with matched controls, with a rate ratio of approximately 5.35 in one analysis.[9]
Clinical cohorts have demonstrated substantial rates of orthostatic intolerance among patients referred for Long-COVID evaluation.[8]
Importantly, the magnitude of prevalence estimates varies enormously according to:
- recruitment method;
- case definition;
- whether symptoms or objective testing are used;
- referral bias;
- age and sex composition;
- duration since infection;
- vaccination status;
- pre-existing autonomic disease.
Accordingly, no single prevalence estimate should be regarded as representative of all people with Long COVID.
IV. Quantitative Evidence of Autonomic Dysfunction
The 2026 study by Keller and colleagues is particularly important because it used quantitative autonomic testing rather than relying solely upon questionnaires.[1]
Patients with Long COVID were compared with individuals with normal autonomic testing and with patients with pure autonomic failure.
Testing included:
- active standing;
- Valsalva manoeuvre;
- respiratory sinus arrhythmia;
- head-up tilt testing;
- beat-to-beat heart-rate and blood-pressure measurement.
The findings demonstrated persistent autonomic abnormalities in Long COVID, while also showing that the pattern differed from the profound autonomic failure observed in classical neurodegenerative autonomic disorders.[1]
This distinction is important.
Long-COVID dysautonomia generally resembles a functional or partial failure of autonomic regulation, rather than complete autonomic denervation.
V. The Physiology of POTS
POTS is not a single physiological disorder.
At least three partially overlapping phenotypes are commonly described:
Neuropathic POTS
Partial peripheral sympathetic denervation produces inadequate vasoconstriction in the lower limbs.
Hypovolaemic POTS
Reduced effective circulating volume limits venous return and stroke volume.
Hyperadrenergic POTS
Excessive sympathetic activation produces marked tachycardia, tremulousness, anxiety-like sensations and sometimes hypertension.
Patients frequently have overlapping features.
The importance of this classification is therapeutic.
A patient with predominantly hypovolaemic POTS may respond differently from one with neuropathic or hyperadrenergic physiology.
VI. Why Tachycardia Occurs
A central haemodynamic relationship is:
Cardiac output = heart rate × stroke volume.
If standing causes a disproportionate reduction in stroke volume, cardiac output can be preserved partly by increasing heart rate.
Thus, tachycardia may be compensatory rather than primary.
A simplified sequence is:
standing
→ venous pooling
→ ↓ venous return
→ ↓ stroke volume
→ sympathetic activation
→ ↑ heart rate.
In POTS, the compensatory increase in heart rate becomes excessive.
This explains why patients often report that simply standing or walking across a room can produce dramatic palpitations.
VII. Cerebral Hypoperfusion
Cardiovascular stability does not necessarily guarantee adequate cerebral perfusion.
Long-COVID studies using transcranial Doppler have identified abnormalities in cerebral blood-flow regulation during orthostatic stress.[10]
The result can be:
standing
→ systemic haemodynamic disturbance
→ reduced cerebral blood-flow velocity
→ cognitive dysfunction/dizziness
→ compensatory sympathetic activation.
This provides a plausible physiological explanation for the characteristic combination of:
upright posture + tachycardia + brain fog.
The patient may not simply be experiencing a subjective sensation.
There may be measurable impairment of cerebral haemodynamics.
VIII. Carbon Dioxide and Cerebral Blood Flow
Carbon dioxide is a potent cerebral vasodilator.
Hyperventilation reduces arterial CO₂.
Reduced CO₂ produces cerebral vasoconstriction.
Consequently:
hyperventilation → ↓ PaCO₂ → cerebral vasoconstriction → ↓ cerebral blood flow.
Patients with Long COVID may develop abnormal breathing patterns, including dysfunctional hyperventilation.
This can interact with autonomic dysfunction.
A patient who becomes dyspnoeic while standing may hyperventilate, lowering CO₂ and further reducing cerebral perfusion.
The result can be:
dizziness + cognitive dysfunction + dyspnoea + tachycardia.
IX. Small-Fiber Neuropathy
The autonomic nervous system depends heavily on small peripheral nerve fibres.
These fibres regulate:
- vasoconstriction;
- sweating;
- heart-rate modulation;
- gastrointestinal function;
- pain;
- temperature.
Small-fiber neuropathy (SFN) can therefore produce both sensory and autonomic symptoms.
Several Long-COVID cohorts have demonstrated evidence of SFN using skin biopsy and other physiological tests.[11,12]
A 2025 multimodal cohort found abnormal skin-biopsy results in 14 of 17 evaluable patients with post-COVID neuropathic pain, and autonomic symptoms were particularly common among those with biopsy abnormalities.[12]
X. Autonomic Small-Fiber Pathology
An important advance came from direct examination of autonomic nerve fibres.
A 2026 histological study of patients with painful Long COVID demonstrated reduced nerve-fibre density in:
- piloerector muscles;
- sweat glands.
Strikingly, autonomic abnormalities were also present in patients whose somatic intraepidermal nerve-fibre density was preserved.[2]
This observation has major implications.
It suggests that:
Autonomic small-fiber injury may occur independently of conventional somatic small-fiber neuropathy.
Thus, a normal standard neurological examination—or even a relatively preserved somatic skin biopsy—does not necessarily exclude autonomic neuropathology.
XI. Endothelial Dysfunction
The autonomic nervous system does not operate independently of the vascular endothelium.
Sympathetic vasoconstriction requires healthy vascular smooth muscle and endothelial signaling.
SARS-CoV-2 can produce endothelial activation and vascular dysfunction.
Persistent endothelial abnormalities could therefore produce:
- impaired vasoconstriction;
- abnormal vascular permeability;
- venous pooling;
- impaired tissue perfusion.
This provides a mechanistic bridge between:
vascular pathology
and
autonomic dysfunction.
The patient’s tachycardia may therefore be compensating for a vascular problem rather than originating solely within the cardiac conduction system.
XII. Blood-Volume Abnormalities
Effective circulating volume is a major determinant of orthostatic tolerance.
Several mechanisms can reduce effective volume:
- inadequate fluid intake;
- renal sodium handling abnormalities;
- impaired renin–angiotensin–aldosterone responses;
- excessive venous pooling;
- increased vascular permeability.
Long-COVID patients may consequently develop a physiological state resembling chronic relative hypovolaemia.
The resulting reduction in stroke volume can provoke compensatory tachycardia.
This mechanism may also explain why fluid and sodium strategies can benefit selected patients.
XIII. The Renin–Angiotensin System
SARS-CoV-2 interacts directly with the renin–angiotensin system through its ACE2 receptor.
ACE2 participates in conversion of angiotensin II into angiotensin-(1–7), which has vasodilatory and counter-regulatory effects.
Perturbation of this system during SARS-CoV-2 infection could theoretically alter:
- vascular tone;
- inflammation;
- endothelial function;
- fluid balance;
- sympathetic regulation.
This is biologically plausible, although the precise contribution of persistent renin–angiotensin dysregulation to Long-COVID dysautonomia remains uncertain.
XIV. Functional Autoantibodies Against GPCRs
One of the most compelling hypotheses concerns antibodies directed against G-protein-coupled receptors (GPCRs).
These receptors include:
- β1-adrenergic receptors;
- β2-adrenergic receptors;
- α1-adrenergic receptors;
- muscarinic receptors;
- angiotensin II type-1 receptors;
- endothelin receptors.
These receptors regulate vascular tone and autonomic signaling.
A pathogenic antibody capable of altering receptor function could theoretically produce a persistent autonomic disorder without destroying the underlying nerve.
This is an attractive explanation for a disease that is:
physiologically severe
but
structurally subtle.
XV. Evidence for GPCR Autoantibodies
Hofmann and colleagues examined 194 patients with Long COVID and identified high frequencies of functional antibodies against several GPCRs, including β2-adrenergic, M2 muscarinic, AT1 and MAS receptors.[3]
Importantly, specific antibody patterns correlated with clinical phenotypes.
β2-adrenergic receptor antibodies were associated with:
- dizziness;
- impaired concentration;
- POTS.
Combinations involving β2 and M2 receptor antibodies were associated with fatigue and PEM.[3]
These observations are intriguing because they connect:
molecular immunology
with
specific autonomic physiology
and
clinical phenotype.
XVI. The 2026 Autoantibody–Vasoregulation Study
Schmitz and colleagues subsequently provided additional evidence linking GPCR antibodies to autonomic and vascular dysfunction.[6]
Patients with post-COVID syndrome and altered autonomic function were studied using:
- GPCR autoantibody profiling;
- heart-rate variability;
- B-cell receptor sequencing;
- T-cell receptor sequencing.
The investigators reported associations between anti-GPCR autoantibodies and abnormalities in autonomic regulation and vasoreactivity, while identifying adaptive immune-repertoire changes consistent with immune remodeling.[6]
This is an important advance because it begins to connect three levels of biology:
autoantibodies → receptor physiology → autonomic phenotype.
Causality, however, remains unresolved.
XVII. The Autoantibody Problem
The presence of an antibody does not establish that it is pathogenic.
Three possibilities must be distinguished:
Pathogenic antibody
The antibody directly alters receptor function.
Epiphenomenal antibody
The antibody reflects immune activation but does not cause disease.
Compensatory antibody
The antibody develops in response to altered receptor signaling.
The distinction requires functional experiments and, ultimately, therapeutic intervention.
XVIII. Genomics and the Autonomic Phenotype
The genomic basis of Long-COVID dysautonomia remains poorly defined.
This is an important gap.
POTS itself is clearly influenced by host susceptibility, but a specific Long-COVID POTS gene has not been established.
Potential genetic pathways include genes controlling:
- adrenergic receptors;
- muscarinic receptors;
- renin–angiotensin signaling;
- vascular tone;
- nitric oxide metabolism;
- immune regulation;
- mitochondrial function;
- sodium and water handling;
- small-fiber development.
Genetic susceptibility may therefore influence the probability that SARS-CoV-2 infection produces persistent autonomic disease without being sufficient by itself.
XIX. Immunogenomics
The emerging use of B-cell receptor (BCR) and T-cell receptor (TCR) sequencing is particularly promising.
If Long-COVID dysautonomia is autoimmune in a subset of patients, one might expect:
- oligoclonal B-cell responses;
- stereotyped receptor sequences;
- persistent antigen-driven selection;
- distinct T-cell repertoires.
The 2026 GPCR-autoantibody study’s integration of adaptive immune-receptor profiling represents an important step toward this type of molecular endotyping.[6]
The ultimate objective would be to determine whether an autoimmune autonomic endotype can be identified prospectively.
XX. Epigenetics
Infection can alter immune-cell transcription through epigenetic mechanisms.
Potential alterations include:
- DNA methylation;
- histone modification;
- chromatin accessibility;
- transcription-factor activity.
Persistent epigenetic changes could maintain abnormal autonomic or immune signaling after the acute infection has resolved.
This may help explain why some patients experience prolonged disease despite the absence of ongoing severe systemic inflammation.
XXI. The Vagus Nerve
The vagus nerve is a major parasympathetic pathway connecting the brain with the heart, lungs and gastrointestinal tract.
It participates in:
- heart-rate control;
- respiratory regulation;
- gastrointestinal motility;
- inflammatory modulation.
Inflammation can alter vagal signaling.
Conversely, vagal activity can influence inflammatory responses through the cholinergic anti-inflammatory pathway.
Thus:
inflammation ↔ vagal dysfunction
may form another feedback loop.
Whether direct vagal neuropathy is a dominant mechanism in Long COVID remains uncertain, but the physiological interaction is highly plausible.
XXII. Gastrointestinal Dysautonomia
Autonomic dysfunction can produce:
- nausea;
- early satiety;
- constipation;
- diarrhoea;
- abdominal pain;
- gastroparesis-like symptoms;
- impaired intestinal motility.
This is particularly important because gastrointestinal symptoms may be interpreted as a primary gastrointestinal disorder when they may partly reflect autonomic dysfunction.
The enteric nervous system interacts continuously with:
- vagal pathways;
- sympathetic pathways;
- immune cells;
- the intestinal microbiome.
Long COVID may therefore produce a gut–brain–autonomic syndrome rather than isolated gastrointestinal disease.
XXIII. Thermoregulatory Dysfunction
Autonomic control of body temperature depends on:
- skin blood flow;
- sweating;
- vasoconstriction;
- shivering;
- metabolic heat production.
Patients with Long COVID frequently report:
- heat intolerance;
- cold intolerance;
- abnormal sweating;
- episodic chills.
These symptoms may reflect dysregulated autonomic thermoregulation rather than abnormalities in core body temperature itself.
XXIV. Bladder and Sexual Function
Autonomic pathways participate in bladder storage and emptying as well as sexual function.
Persistent autonomic dysfunction could theoretically contribute to:
- urinary urgency;
- frequency;
- impaired bladder emptying;
- erectile dysfunction.
However, these manifestations are nonspecific and require appropriate urological and neurological evaluation.
They should not automatically be attributed to dysautonomia.
XXV. The Interaction with Mitochondrial Dysfunction
Autonomic dysfunction and mitochondrial dysfunction may be mutually reinforcing.
Mitochondrial dysfunction can impair:
- autonomic neurons;
- vascular smooth muscle;
- skeletal muscle;
- cardiac reserve.
Autonomic dysfunction can impair:
- oxygen delivery;
- tissue perfusion;
- exercise adaptation.
Thus:
mitochondrial dysfunction ↔ autonomic dysfunction
could form another feed-forward system.
This is particularly relevant to fatigue and PEM.
XXVI. Exercise Intolerance
Exercise requires rapid coordination among:
- the heart;
- blood vessels;
- autonomic nervous system;
- lungs;
- skeletal muscle;
- mitochondria.
A patient with Long-COVID dysautonomia may have:
inadequate venous return
excessive tachycardia
abnormal vasoconstriction
impaired cerebral perfusion
skeletal-muscle bioenergetic limitation.
The result is severe exercise intolerance.
This is why exercise capacity can be profoundly reduced even when routine cardiac and pulmonary investigations appear relatively normal.
XXVII. Post-Exertional Malaise
Autonomic dysfunction may be particularly important in PEM.
Exertion produces:
- increased sympathetic activation;
- increased heart rate;
- increased vascular demand;
- increased metabolic demand.
If autonomic reserve is impaired, the physiological stress may be disproportionately large.
A possible sequence is:
exercise
→ sympathetic activation
→ inadequate vascular compensation
→ reduced tissue/cerebral perfusion
→ metabolic stress
→ inflammatory signaling
→ delayed multisystem deterioration.
This mechanism is compatible with, but does not fully explain, PEM.
PEM is likely to involve additional metabolic and immune mechanisms.
XXVIII. Sex Differences
Long-COVID dysautonomia disproportionately affects women in many clinical cohorts.
This parallels the epidemiology of POTS and several autoimmune diseases.
Potential explanations include:
- sex hormones;
- immune-response differences;
- vascular biology;
- autonomic regulation;
- genetic factors involving the X chromosome.
The observation is epidemiologically robust enough to merit mechanistic investigation but should not be interpreted as proof of a particular biological mechanism.
XXIX. Age
Autonomic dysfunction can occur in both adults and children.
A 2025 pediatric study of 92 children with Long COVID undergoing passive standing testing documented clinically important orthostatic intolerance.[13]
Children may present differently from adults, with:
- exercise avoidance;
- school impairment;
- headache;
- abdominal symptoms;
- fatigue;
- dizziness.
Because children may have difficulty articulating orthostatic symptoms, clinicians must actively inquire about posture-dependent symptom changes.
XXX. Clinical Course
Long-COVID autonomic disease has several recognizable trajectories.
Early postviral dysautonomia
Symptoms begin during or shortly after acute infection.
Delayed autonomic syndrome
The patient initially recovers and subsequently develops orthostatic symptoms.
POTS-dominant disease
Tachycardia and orthostatic intolerance dominate.
Neuropathic dysautonomia
Sensory symptoms and small-fiber abnormalities accompany autonomic dysfunction.
Hyperadrenergic phenotype
Tachycardia, tremulousness and sympathetic overactivation predominate.
Multisystem dysautonomia
Cardiovascular, gastrointestinal, thermoregulatory, neurological and urinary systems become involved.
Relapsing disease
Symptoms fluctuate substantially over time.
XXXI. Natural History
The natural history remains incompletely characterised.
Some patients improve over months.
Others remain symptomatic for years.
A 2025 study of cardiovascular autonomic disorders following COVID-19 infection or vaccination reported longitudinal outcomes and documented a spectrum of newly diagnosed and exacerbated autonomic disorders.[14]
The heterogeneous natural history strongly suggests that “Long-COVID dysautonomia” is not a single disease.
Instead, it likely represents several biological trajectories sharing common physiological manifestations.
XXXII. Diagnostic Strategy
A rational evaluation begins with a careful history.
Patients should be asked:
- Do symptoms worsen while standing?
- Do they improve after lying down?
- Does the heart race after standing?
- Does showering provoke symptoms?
- Does prolonged standing cause weakness or cognitive impairment?
- Are symptoms worse in heat?
- Does eating provoke tachycardia?
- Are there episodes of near-syncope?
- Does exertion cause delayed deterioration?
These questions can reveal dysautonomia even when the patient does not use the term “orthostatic.”
XXXIII. Bedside Testing
A simple standing test can provide important information.
Heart rate and blood pressure are measured supine and then during standing for up to 10 minutes when appropriate.
Abnormal findings may include:
- excessive heart-rate increase;
- orthostatic hypotension;
- delayed blood-pressure instability;
- symptoms without large blood-pressure changes.
Formal tilt-table testing can provide more controlled assessment.
XXXIV. Formal Autonomic Testing
A comprehensive autonomic laboratory assessment may include:
- head-up tilt;
- Valsalva manoeuvre;
- deep-breathing heart-rate variability;
- sudomotor testing;
- beat-to-beat blood-pressure measurement.
Additional investigations may include:
- transcranial Doppler;
- skin biopsy;
- quantitative sensory testing;
- catecholamines;
- plasma volume assessment;
- cardiopulmonary exercise testing.
The objective is not merely to label the patient with POTS.
It is to identify which physiological component has failed.
XXXV. Differential Diagnosis
Autonomic symptoms are nonspecific.
The differential diagnosis includes:
- anaemia;
- dehydration;
- adrenal insufficiency;
- thyroid disease;
- cardiac arrhythmia;
- structural heart disease;
- medication effects;
- infection;
- diabetes;
- peripheral neuropathy;
- Parkinsonian autonomic failure;
- multiple-system atrophy;
- anxiety-related hyperventilation;
- deconditioning.
A diagnosis of Long-COVID dysautonomia should therefore be based on clinical context and objective physiology rather than symptom attribution alone.
XXXVI. Treatment: Physiological Restoration
Treatment begins with correction of reversible contributors.
Depending upon individual circumstances, strategies may include:
- adequate hydration;
- increased dietary sodium when medically appropriate;
- compression garments;
- avoidance of excessive heat;
- gradual changes in posture;
- recumbent or semi-recumbent activity;
- sleep optimisation;
- treatment of coexisting disorders.
Because many patients have PEM, rehabilitation must be individualised.
The evidence does not justify indiscriminate graded exercise therapy for patients with significant PEM.[15]
XXXVII. Pharmacological Treatment
No single medication treats all Long-COVID dysautonomia.
Depending upon phenotype, clinicians may consider:
β-blockers
Reduce excessive heart rate.
Ivabradine
Slows sinus-node activity without the same degree of blood-pressure reduction associated with some β-blockers.
Midodrine
Increases vascular tone and can reduce orthostatic pooling.
Fludrocortisone
Promotes sodium retention and volume expansion in selected patients.
Pyridostigmine
May enhance parasympathetic and autonomic ganglionic signaling.
Treatment should be phenotype-specific and monitored carefully.
A 2025 scoping review concluded that the evidence base for pharmacological and non-pharmacological treatment of Long-COVID autonomic dysfunction remains limited and heterogeneous.[16]
XXXVIII. Immunotherapy
If autoimmune autonomic dysfunction is confirmed in a subset of patients, immunotherapy becomes an attractive possibility.
Potential approaches include:
- intravenous immunoglobulin;
- corticosteroids;
- plasma exchange;
- B-cell-directed therapy.
However, evidence remains preliminary.
Case series and observational studies cannot establish efficacy.
A small 2024 therapeutic-apheresis study reported reductions in receptor autoantibodies accompanied by symptomatic improvement in many patients, but the uncontrolled design prevents causal inference.[17]
Randomised trials are required.
XXXIX. Why Antiviral Therapy May Matter
If persistent SARS-CoV-2 antigen or viral reservoirs initiate immune dysregulation, antiviral therapy could theoretically modify downstream autonomic disease.
However, a phase 2 randomised trial of nirmatrelvir–ritonavir in people with established Long COVID did not demonstrate a clear overall clinical benefit sufficient to establish routine antiviral treatment for Long COVID.[18]
This finding is important.
It suggests that if persistent viral activity contributes to dysautonomia, the relationship may be:
heterogeneous, tissue-specific and temporally dependent.
Antivirals may need to be targeted to molecularly defined patients rather than administered indiscriminately.
XL. Autonomic Dysfunction as a Systems Disease
The evidence increasingly suggests that Long-COVID dysautonomia is not confined to the autonomic nerves.
It involves a network:
immune system
↕
autonomic nervous system
↕
vascular endothelium
↕
microcirculation
↕
brain
↕
skeletal muscle
↕
mitochondria
↕
gastrointestinal tract.
This systems model explains why the same patient can experience tachycardia, brain fog, neuropathic pain, gastrointestinal dysfunction and exercise intolerance.
These may be manifestations of a shared physiological disturbance rather than separate diseases.
XLI. A Unified Pathophysiological Model
A plausible sequence is:
SARS-CoV-2 infection
↓
innate and adaptive immune activation
↓
endothelial and neuroimmune injury
↓
autonomic small-fiber dysfunction
functional GPCR autoantibodies
altered blood-volume regulation
abnormal vascular tone
↓
venous pooling and reduced stroke volume
↓
excess sympathetic activation
↓
tachycardia
↓
impaired cerebral and peripheral perfusion
↓
cognitive dysfunction + fatigue + exercise intolerance
↓
metabolic stress
↓
post-exertional exacerbation
↓
further autonomic and inflammatory activation.
This is a mechanistic model rather than an established sequence occurring in every patient.
XLII. The Role of Genomic Endotyping
The future of Long-COVID autonomic medicine will probably involve molecular endotyping.
Potential categories include:
Autoimmune autonomic endotype
GPCR antibodies and adaptive immune abnormalities.
Neuropathic endotype
Small-fiber loss and impaired autonomic innervation.
Hypovolaemic endotype
Reduced effective circulating volume.
Hyperadrenergic endotype
Excess sympathetic activation.
Vascular endotype
Endothelial and microvascular dysfunction.
Neurovascular endotype
Orthostatic cerebral hypoperfusion.
Metabolic endotype
Mitochondrial and bioenergetic dysfunction.
These categories are not mutually exclusive.
Indeed, multimorbidity within a single patient may be the rule rather than the exception.
XLIII. What Would Establish Causality?
The most important unanswered question is whether autonomic dysfunction is:
a primary cause of Long-COVID symptoms,
a downstream consequence,
or
a perpetuating mechanism.
Several experiments could answer this.
If pathogenic GPCR antibodies are causal, antibody removal should produce predictable physiological improvement.
If small-fiber injury is causal, nerve regeneration should correlate with autonomic recovery.
If hypovolaemia is dominant, restoration of plasma volume should normalize orthostatic physiology.
If persistent viral antigen drives the disorder, targeted antiviral therapy should improve both viral and autonomic biomarkers.
These are testable propositions.
XLIV. Conclusions
Autonomic dysfunction has progressed from a clinically plausible explanation for a subset of Long-COVID symptoms to a measurable, increasingly well-characterised physiological phenotype.
The evidence now encompasses:
- epidemiological associations;
- quantitative autonomic testing;
- tilt-table abnormalities;
- impaired heart-rate variability;
- cerebral haemodynamic abnormalities;
- small-fiber pathology;
- autonomic nerve-fibre loss;
- functional GPCR autoantibodies;
- immune-repertoire alterations;
- and longitudinal clinical observations.[1–6,8,9,12–14]
The convergence of these observations is significant.
Yet the field must resist the temptation to replace one oversimplification with another.
Long COVID is not synonymous with POTS.
POTS is not synonymous with autonomic neuropathy.
Autonomic neuropathy is not synonymous with autoimmunity.
And the presence of GPCR antibodies does not by itself establish pathogenic autoimmunity.
The most defensible current model is that SARS-CoV-2 can trigger a heterogeneous neuroimmune–vascular disorder of autonomic regulation.
In susceptible individuals, infection may produce persistent immune activation, functional autoantibodies, autonomic small-fiber injury, endothelial dysfunction, altered blood-volume regulation and abnormal sympathetic control. These processes may interact to impair cardiovascular compensation during standing and exercise, producing tachycardia, cerebral hypoperfusion, fatigue, cognitive dysfunction and exercise intolerance.
The clinical importance of this model is considerable.
Autonomic dysfunction is potentially detectable, phenotypable and treatable.
The next generation of Long-COVID research should therefore move beyond symptom inventories toward integrated physiological and molecular phenotyping:
tilt physiology + cerebral blood flow + small-fiber pathology + GPCR autoantibodies + immune-receptor sequencing + endothelial function + metabolic profiling + longitudinal clinical outcomes.
Such studies may finally identify which patients have an autoimmune autonomic disorder, which have neuropathic dysautonomia, which have vascular or hypovolaemic disease, and which have combinations of these mechanisms.
The ultimate objective is not merely to demonstrate that autonomic dysfunction exists.
It is to determine why it exists in a particular patient and which biological intervention can reverse it.
That transition—from syndromic recognition to mechanistic precision—is likely to define the next phase of Long-COVID medicine.
Numbered References
- Keller C, Mascarenhas L, Reyes JL, Duval S, Benditt DG. Association of Autonomic Dysfunction With Long COVID: Evaluation Using Quantitative Autonomic Testing. J Am Coll Cardiol. 2026;87:216–230. doi:10.1016/j.jacc.2025.09.1608.
- Falco A, Galosi E, Litewczuk M, et al. Autonomic small fiber involvement in painful long COVID: a histological and clinical study. 2026. Skin-biopsy evidence demonstrated reduced piloerector-muscle and sweat-gland autonomic nerve-fiber density, including in patients with preserved somatic intraepidermal nerve-fiber density.
- Hofmann S, et al. Functional Autoantibodies Targeting G-Protein-Coupled Receptors and Their Clinical Phenotype in Patients with Long-COVID. Int J Mol Sci. 2025.
- Gunning WT III, et al. Postural orthostatic tachycardia syndrome in post-COVID-19 condition. 2025. The study identified a POTS phenotype among patients with post-COVID illness and examined platelet abnormalities.
- Autoantibodies in patients with post-COVID syndrome: a possible link with severity? Study of α1-, β2-adrenergic and muscarinic-receptor antibodies in patients with post-COVID syndrome. 2024.
- Schmitz B, Garbsch R, Schäfer H, et al. Autonomic dysfunction and vasoregulation in long COVID-19 are linked to anti-GPCR autoantibodies. J Allergy Clin Immunol. 2026;157:722–738.e7. doi:10.1016/j.jaci.2025.10.034.
- Dani M, Dirksen A, Taraborrelli M, et al. Autonomic dysfunction in ‘long COVID’: rationale, physiology and management strategies. Clin Med (Lond). 2021;21:e63–e67. doi:10.7861/clinmed.2020-0896.
- High Incidence of Autonomic Dysfunction and Postural Orthostatic Tachycardia Syndrome in Patients with Long COVID: Implications for Management and Health Care Planning. JACC. 2023. Prospective autonomic testing showed reduced respiratory sinus arrhythmia and excessive orthostatic heart-rate responses in PASC.
- Kwan AC, et al. Apparent risks of postural orthostatic tachycardia syndrome after SARS-CoV-2 infection. Nature Cardiovascular Research. 2022. The study found substantially increased POTS-associated diagnoses following SARS-CoV-2 infection.
- Long-COVID autonomic studies incorporating transcranial Doppler have demonstrated abnormalities in orthostatic cerebral blood-flow regulation. See contemporary autonomic Long-COVID cohorts and the 2026 literature on cerebral hypoperfusion.
- Oaklander AL, et al. Peripheral Neuropathy Evaluations of Patients With Prolonged Long COVID. Neurol Neuroimmunol Neuroinflamm. 2022. Objective neuropathic abnormalities were identified in a substantial proportion of evaluated patients.
- Drobinska N, Nehme M, Assal F, Laffitte E, Guessous I, Lascano AM. Small Fiber Neuropathy in Long COVID: A Cohort Study with Multimodal Assessment and Follow-Up. 2025.
- Morrow AK, et al. Orthostatic Intolerance in Children With Long COVID. 2025. Prospective assessment of 92 children in a post-COVID rehabilitation setting.
- Leys F, et al. Postural orthostatic tachycardia syndrome is the most frequent cardiovascular autonomic disorder after COVID-19 infection or vaccination. 2025. Longitudinal assessment of newly diagnosed and exacerbated cardiovascular autonomic disorders.
- Fedorowski A, et al. Cardiovascular autonomic dysfunction in post-COVID-19 syndrome: a major health-care burden. Nat Rev Cardiol. 2024;21. The authors emphasised the importance of distinguishing autonomic dysfunction from inappropriate exercise prescriptions in patients with PEM.
- Treadwell JR, Wagner J, Reston JT, et al. Treatments for Long COVID autonomic dysfunction: a scoping review. Clin Auton Res. 2025;35:5–29. doi:10.1007/s10286-024-01081-w.
- Korth J, et al. A Single-Center Pilot Study of Therapeutic Apheresis in Patients with Severe Post-COVID Syndrome. Horm Metab Res. 2024;56:869–874.
- Sawano M, Bhattacharjee B, Caraballo C, et al. Nirmatrelvir–ritonavir versus placebo–ritonavir in individuals with long COVID in the USA (PAX LC): a double-blind, randomised, placebo-controlled, phase 2, decentralised trial. Lancet Infect Dis. 2025;25:936–946. doi:10.1016/S1473-3099(25)00073-8.