Small fiber neuropathy in children, adolescents, and young adults with chronic orthostatic intolerance and postural orthostatic tachycardia syndrome: A retrospective study.

PURPOSE: To determine in children, adolescent and young adult (CAYA) patients presenting with Orthostatic Intolerance (OI) or Postural Orthostatic Tachycardia Syndrome (POTS) associated with the additional symptoms of neuropathic discomfort (pain, paresthesia and/or allodynia): 1) the incidence of small fiber neuropathy, and 2) assess if there was serologic evidence for an underlying inflammatory or autoimmune state. METHODS: A cohort of 109 CAYA patients with the above symptoms underwent epidermal skin biopsy for nerve fiber density. Blood biomarkers for inflammation were tested (CRP, ESR, ANA, complement (C3), thyroid function testing with antibodies (thyroid peroxidase antibody and thyroglobulin antibody), and cytokine panel 13). Patients completed a Quality of Health questionnaire. Statistical analysis was performed using Wilcoxon rank sum tests. RESULTS: In CAYA patients with OI or POTS and neuropathic symptoms, skin biopsy for small fiber neuropathy was abnormal in 53 %. The sample population was predominantly female and Caucasian with moderately decreased perceived quality of health. OI /POTS patients with small fiber neuropathy had a 3-fold probability of having a positive ANA or anti-thyroid antibody, suggesting an underlying autoimmune or inflammatory process. CONCLUSION: Our data suggest a link between OI and POTS and small fiber neuropathy. Small fiber neuropathy was found by skin biopsy in over half of the patients tested. OI and Postural orthostatic tachycardia patients with small fiber neuropathy expressed multiple markers suggesting an underlying autoimmune or inflammatory process. Future research will be done to evaluate the symptomatic implication of SFN and whether immune or pharmacologic manipulation can alter patient symptoms.

An online survey of pelvic congestion support group members regarding comorbid symptoms and syndromes.

OBJECTIVES: Patients with pelvic congestion syndrome (PCS) often report overlapping somatic symptoms and syndromes. The objective of this study was to explore the prevalence of co-existing symptoms and self-reported syndrome diagnoses among women with PCS and to inform future research hypotheses. METHODS: A brief online survey was offered to members of a PCS support group website. Responses were assessed for self-reported co-existing symptoms and formal diagnoses, including: chronic fatigue syndrome, fibromyalgia, postural tachycardia syndrome, irritable bowel syndrome, migraines, interstitial cystitis, and temporomandibular joint dysfunction. RESULTS: Of a total of 6000 members, there were 398 respondents; 232 (59%) had not yet been treated for PCS. Among these, the most prevalent co-existing symptoms were as follows: severe fatigue (72%), dizziness (63%), IBS symptoms (61%), brain fog (33%), migraines (49%), polyuria or dysuria (41%), excessive sweating (31%), TMJ pain (31%), and loose skin or lax joints (18%). These are much higher than reported for the general female population. The most commonly self-reported comorbid syndrome diagnoses for the overall group of 398 were: irritable bowel syndrome (29%), fibromyalgia (13%), spinal nerve problems (18%), interstitial cystitis (10%), postural tachycardia syndrome (9%), hypertension (11%), chronic fatigue syndrome (10%), and Ehlers-Danlos syndrome (6%). Other than with hypertension, these rates are variably higher than in the general population. CONCLUSION: Several self-reported co-existing symptoms and syndromes are more prevalent in members of a PCS support group relative to the reported prevalence in the general population. More formal investigation is warranted to evaluate this finding and to investigate potential etiologic links. Ehlers-Danlos Syndrome appears to be common in self identifying PCS women.

Faintly tired: a systematic review of fatigue in patients with orthostatic syncope.

BACKGROUND: Orthostatic syncope (transient loss of conscious when standing-fainting) is common and negatively impacts quality of life. Many patients with syncope report experiencing fatigue, sometimes with "brain fog", which may further impact their quality of life, but the incidence and severity of fatigue in patients with syncope remain unclear. In this systematic review, we report evidence on the associations between fatigue and conditions of orthostatic syncope. METHODS: We performed a comprehensive literature search of four academic databases to identify articles that evaluated the association between orthostatic syncope [postural orthostatic tachycardia syndrome (POTS), vasovagal syncope (VVS), orthostatic hypotension (OH)] and fatigue. Studies were independently screened using a multi-stage approach by two researchers to maintain consistency and limit bias. RESULTS: Our initial search identified 2797 articles, of which 13 met our inclusion criteria (POTS n = 10; VVS n = 1; OH n = 1; VVS and POTS n = 1). Fatigue scores were significantly higher in patients with orthostatic syncope than healthy controls, and were particularly severe in those with POTS. Fatigue associated with orthostatic syncope disorders spanned multiple domains, with each dimension contributing equally to increased fatigue. "Brain fog" was an important symptom of POTS, negatively affecting productivity and cognition. Finally, fatigue was negatively associated with mental health in patients with POTS. CONCLUSION: In conditions of orthostatic syncope, fatigue is prevalent and debilitating, especially in patients with POTS. The consideration of fatigue in patients with orthostatic disorders is essential to improve diagnosis and management of symptoms, thus improving quality of life for affected individuals.

Proposed subtypes of post-COVID-19 syndrome (or long-COVID) and their respective potential therapies.

The effects of coronavirus disease 2019 (COVID-19), a highly transmissible infectious respiratory disease that has initiated an ongoing pandemic since early 2020, do not always end in the acute phase. Depending on the study referred, about 10%-30% (or more) of COVID-19 survivors may develop long-COVID or post-COVID-19 syndrome (PCS), characterised by persistent symptoms (most commonly fatigue, dyspnoea, and cognitive impairments) lasting for 3 months or more after acute COVID-19. While the pathophysiological mechanisms of PCS have been extensively described elsewhere, the subtypes of PCS have not. Owing to its highly multifaceted nature, this review proposes and characterises six subtypes of PCS based on the existing literature. The subtypes are non-severe COVID-19 multi-organ sequelae (NSC-MOS), pulmonary fibrosis sequelae (PFS), myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS), postural orthostatic tachycardia syndrome (POTS), post-intensive care syndrome (PICS) and medical or clinical sequelae (MCS). Original studies supporting each of these subtypes are documented in this review, as well as their respective symptoms and potential interventions. Ultimately, the subtyping proposed herein aims to provide better clarity on the current understanding of PCS.

Association between quadrivalent human papillomavirus vaccination and selected syndromes with autonomic dysfunction in Danish females: population based, self-controlled, case series analysis.

OBJECTIVE: To evaluate the association between quadrivalent human papillomavirus vaccination and syndromes with autonomic dysfunction, such as chronic fatigue syndrome, complex regional pain syndrome, and postural orthostatic tachycardia syndrome. DESIGN: Population-based self-controlled case series. SETTING: Information on human papillomavirus vaccinations and selected syndromes with autonomic dysfunction (chronic fatigue syndrome, complex regional pain syndrome, and postural orthostatic tachycardia syndrome) identified using ICD-10 (international classification of diseases, revision 10) diagnostic codes from Danish nationwide registers. PARTICIPANTS: 869 patients with autonomic dysfunction syndromes from a cohort of 1 375 737 Danish born female participants aged 10 to 44 years during 2007-16. MAIN OUTCOME MEASURES: Self-controlled case series rate ratios (95% confidence intervals) of the composite outcome of chronic fatigue syndrome, complex regional pain syndrome, and postural orthostatic tachycardia syndrome, adjusted for age and season, comparing female participants vaccinated and unvaccinated with the quadrivalent human papillomavirus vaccine. Chronic fatigue syndrome, complex regional pain syndrome, and postural orthostatic tachycardia syndrome were also considered separately in secondary analyses. RESULTS: During 10 581 902 person years of follow-up, 869 female participants with syndromes of autonomic dysfunction (136 with chronic fatigue syndrome, 535 with complex regional pain syndrome, and 198 with postural orthostatic tachycardia syndrome) were identified. Quadrivalent human papillomavirus vaccination did not statistically significantly increase the rate of a composite outcome of all syndromes with autonomic dysfunction in a 365 day risk period following vaccination (rate ratio 0.99, 95% confidence interval 0.74 to 1.32) or the rate of any individual syndrome in the risk period (chronic fatigue syndrome (0.38, 0.13 to 1.09), complex regional pain syndrome (1.31, 0.91 to 1.90), or postural orthostatic tachycardia syndrome (0.86, 0.48 to 1.54)). CONCLUSIONS: When vaccination is introduced, adverse events could occur in close temporal relation to the vaccine purely by chance. These results do not support a causal association between quadrivalent human papillomavirus vaccination and chronic fatigue syndrome, complex regional pain syndrome, or postural orthostatic tachycardia syndrome, either individually or as a composite outcome. An increased risk of up to 32% cannot be formally excluded, but the statistical power of the study suggests that a larger increase in the rate of any syndrome associated with vaccination is unlikely.

Functional gastrointestinal disorders are increased in joint hypermobility-related disorders with concomitant postural orthostatic tachycardia syndrome.

BACKGROUND: Individuals with hypermobility spectrum disorders/hypermobile Ehlers-Danlos syndrome (HSD/hEDS) frequently fulfill criteria for Rome IV functional gastrointestinal disorders (FGIDs). Postural orthostatic tachycardia syndrome (POTS) is also commonly reported in HSD/hEDS and may impact on co-morbidity with and severity of FGIDs, although this remains to be studied. We determined the impact of concomitant POTS and HSD/hEDS on their association with Rome IV FGIDs. METHODS: With the help of the charity organization Ehlers-Danlos Support UK, an online cross-sectional health survey was completed by individuals with HSD/hEDS. The survey enquired for (a) self-reported doctor diagnosis of POTS, chronic fatigue syndrome, and fibromyalgia, (b) the presence and symptom frequency of Rome IV FGIDs, and (c) anxiety and depression scores. KEY RESULTS: Of 616 subjects with HSD/hEDS, 37.5% reported a doctor diagnosis of POTS. POTS-positive individuals were significantly younger than POTS-negative subjects (37 vs 40 years, P = 0.002), more likely to report chronic fatigue syndrome (44% vs 31%, P < 0.0001), and showed a trend toward increased prevalence of fibromyalgia (44% vs 37%, P = 0.06) and higher depression score (P = 0.07). POTS-positive subjects were also more likely to fulfill criteria for Rome IV FGIDs across various organ domains and experienced both upper and lower gastrointestinal symptoms significantly more frequently. The increased associations for FGIDs and GI symptom frequency remained unchanged in HSD/hEDS subjects with POTS following adjustments for age, chronic fatigue syndrome, fibromyalgia, and depression scores. CONCLUSIONS AND INFERENCES: The high FGID burden in HSD/hEDS is further amplified in the presence of POTS. Future studies should elucidate the mechanism by which POTS arises in HSD/hEDS and is associated with increased GI symptoms.

Nutcracker syndrome mimicking new daily persistent headache: A case report.

INTRODUCTION: Compression of the duodenum and left renal vein between the aorta and superior mesenteric artery usually leads to symptoms of proximal bowel obstruction or hematuria and, more rarely, nonspecific mild headaches. CASE: A young woman presented with new daily persistent headache refractory to numerous pharmacological treatments, onabotulinumtoxinA, nerve blocks, and occipital nerve stimulation. Following several years of daily severe headache, worsening abdominal pain and intolerance for food intake led to the discovery of aortomesenteric compression. Surgical treatment gave prompt improvement in gastric symptoms but also essentially resolved the headache. CONCLUSION: This is the first description of new daily persistent headache in association with aortomesenteric compression as well as marked improvement of headache following aortomesenteric decompression. In patients with new daily persistent headache and orthostatic symptoms one may consider a differential diagnosis of Nutcracker syndrome, especially in patients with comorbid hypermobility syndromes, hematuria or gastric symptoms.

Human papillomavirus (HPV) vaccine and autonomic disorders: a position statement from the American Autonomic Society.

INTRODUCTION: Human papillomavirus (HPV) vaccination has been anecdotally connected to the development of dysautonomia, chronic fatigue, complex regional pain syndrome and postural tachycardia syndrome. OBJECTIVES: To critically evaluate a potential connection between HPV vaccination and the above-noted conditions. METHODS: We reviewed the literature containing the biology of the virus, pathophysiology of infection, epidemiology of associated cancers, indications of HPV vaccination, safety surveillance data and published reports linking HPV vaccination to autonomic disorders. RESULTS: At this time, the American Autonomic Society finds that there are no data to support a causal relationship between HPV vaccination and CRPS, chronic fatigue, and postural tachycardia syndrome to other forms of dysautonomia. CONCLUSION: Certain conditions are prevalent in the same populations that are vaccinated with the HPV vaccine (peri-pubertal males and females). This association, however, is an insufficient proof of causality.

Postural Tachycardia Syndrome (POTS) and the GI Tract: A Primer for the Gastroenterologist.

Postural tachycardia syndrome (POTS) is one of the most common causes of orthostatic intolerance and is being increasingly recognized in clinical practice. Gastrointestinal (GI) symptoms are reported commonly in patients with POTS and pose a considerable management challenge, making it imperative that gastroenterologists be aware of this condition and its GI comorbidities. Although the evidence presented herein does not prove causation, it does support an association between GI symptoms, GI dysmotility, and POTS. At present, the evaluation and treatment of GI symptoms in patients with POTS remains largely empirical. General measures to treat POTS may lead to improvement in both GI and non-GI symptoms. GI symptoms refractory to these measures should prompt further diagnostic evaluation of gastrointestinal dysmotility and appropriate dietary and pharmacologic management. This review focuses its attention on the involvement of the GI tract in POTS including a discussion of GI symptoms and conditions associated with POTS, followed by an analysis of abnormalities in gut physiology described in POTS, and concluding with an overview of management and suggestions for research directions.

Association of Postural Tachycardia Syndrome and Ehlers-Danlos Syndrome with Mast Cell Activation Disorders.

Mast cell activation disorders (MCADs) consist of episodic systemic symptoms due to mast cell mediator release. Diagnosis is based on clinical presentation and determination of high levels of tryptase or histamine. Ehlers-Danlos syndrome (EDS) and postural tachycardia syndrome (POTS) frequently coexist. It has been described that individuals with these syndromes can even present symptoms compatible to MCADs, which could represent a new specific phenotype. Preliminary genetic data suggest a role for tryptase in the pathogenesis of MCADs, EDS, and POTS association. Studies with larger samples evaluating clinics, genetics, and histopathology are required to define the real correlation between these 3 clinical entities.

Postural orthostatic tachycardia syndrome and the potential role of mast cell activation.

Though a sizeable amount of data connects mast cell activity to the neurologic system, less is known about the true clinical implications of this relationship. Even less is understood about treatment strategies in those with both allergic and neurologic complaints. This is particularly true in postural orthostatic tachycardia syndrome (POTS), a common type of dysautonomia, where patients are burdened by symptoms of orthostatic cerebral hypoperfusion and several other comorbidities that are likely influenced by autonomic tone. Some patients describe characteristic allergic symptoms, in the absence of typical IgE mediated triggers, and also improvement with traditional mast cell directed medications. Further work is necessary to determine whether these anecdotal observations are valid. The answer to this question will likely be addressed as the mechanisms of POTS are better characterized, which may include a phenotype with distinct mast cell involvement.

Postural Orthostatic Tachycardia Syndrome: Prevalence, Pathophysiology, and Management.

Postural orthostatic tachycardia syndrome (POTS) is a debilitating disease that predominantly affects young women. It is a multifactorial disorder that is characterized by severe tachycardia and orthostatic intolerance. Patients with POTS experience a variety of cardiac, neurological, and immunological symptoms that significantly reduce quality of life. In this review, a comprehensive framework is provided to aid in helping identify and treat patients with POTS. Given its heterogenous nature, it is crucial to understand each component of POTS in relation to one another instead of distinct parts. The framework highlights the overlap among the five main subtypes of POTS based on its pathophysiology (neuropathic, hypovolemic, primary hyperadrenergic, joint-hypermobility-related, and immune-related). Emphasis is placed on incorporating a multidisciplinary approach when treating patients with POTS, especially with a new focus towards immunotherapy. Although research has advanced our knowledge of POTS, there is still a critically unmet need to further our understanding and provide patients with the relief they need.

Postural tachycardia syndrome and other forms of orthostatic intolerance in Ehlers-Danlos syndrome.

OBJECTIVE: To review the association between orthostatic intolerance syndromes and both joint hypermobility and Ehlers-Danlos syndrome, and to propose reasons for identifying hereditary connective tissue disorders in those with orthostatic intolerance in the context of both clinical care and research. METHODS: We searched the published peer-reviewed medical literature for papers reporting an association between joint hypermobility or Ehlers-Danlos syndrome and orthostatic intolerance. RESULTS: We identified 10 relevant papers. Although methodological variability between studies introduces some limitations, the published literature consistently identifies a significantly higher prevalence of orthostatic intolerance symptoms in patients with joint hypermobility or Ehlers-Danlos syndrome than in healthy controls, and a significantly higher prevalence of cardiovascular and autonomic abnormalities both at rest and during orthostatic challenge. Postural tachycardia syndrome is the most commonly recognized circulatory disorder. The severity of orthostatic symptoms in those with EDS correlates with impairments in quality of life. CONCLUSION: There is a strong association between several forms of cardiovascular dysfunction, most notably postural tachycardia syndrome, and joint hypermobility or Ehlers-Danlos syndrome. We propose that recognition of joint hypermobility and Ehlers-Danlos syndrome among those with orthostatic intolerance syndromes has the potential to improve clinical care and the validity of research findings.

Demographics of a large paediatric Postural Orthostatic Tachycardia Syndrome Program.

OBJECTIVE: The aim of this study was to identify and evaluate demographic and clinical features of paediatric patients with postural orthostatic tachycardia syndrome in a tertiary hospital speciality clinic. METHOD: This is a retrospective review of clinical data obtained during initial outpatient evaluation. RESULTS: A total of 708 patients met the evaluation criteria. Female patients outnumbered males, 3.45:1. Caucasians were over-represented at 94.1% of patients. Median age at diagnosis was 15.7 years. Joint hypermobility occurred in 57.3% of patients; 22.4% had hypermobile Ehlers-Danlos syndrome; and 34.9% had hypermobility spectrum disorder. Median age of onset of symptoms was 12.6 years in patients with hypermobility versus 13.7 years in those without (p=0.0001). Median duration of symptoms was 3.3 years with hypermobility versus 1.5 years without (p<0.00001). Putative triggers included infection in 23.6% of patients, concussion in 11.4%, and surgery/trauma in 2.8%. Concurrent inflammatory disorders were noted in 5.2% of patients. Six symptoms comprised 80% of initial patient complaints. Overall, 66% of patients subsequently had at least 10 symptoms, 50% had at least 14 symptoms, and 30% reported at least 26 symptoms. Symptoms were largely cardiovascular, gastrointestinal, and neurological. Paediatric patients with postural orthostatic tachycardia syndrome seen in a large speciality clinic are predominantly female, are mostly Caucasian, have onset of symptoms in early adolescence, and have symptoms for over two years before diagnosis. Over half of patients have joint hypermobility. More than one-third of patients have a possible autoimmune or inflammatory trigger, including infection, concussion, or surgery/trauma. Patients experience symptoms that are highly variable and multi-system in origin over the course of illness.

Pediatric Disorders of Orthostatic Intolerance.

Orthostatic intolerance (OI), having difficulty tolerating an upright posture because of symptoms or signs that abate when returned to supine, is common in pediatrics. For example, ∼40% of people faint during their lives, half of whom faint during adolescence, and the peak age for first faint is 15 years. Because of this, we describe the most common forms of OI in pediatrics and distinguish between chronic and acute OI. These common forms of OI include initial orthostatic hypotension (which is a frequently seen benign condition in youngsters), true orthostatic hypotension (both neurogenic and nonneurogenic), vasovagal syncope, and postural tachycardia syndrome. We also describe the influences of chronic bed rest and rapid weight loss as aggravating factors and causes of OI. Presenting signs and symptoms are discussed as well as patient evaluation and testing modalities. Putative causes of OI, such as gravitational and exercise deconditioning, immune-mediated disease, mast cell activation, and central hypovolemia, are described as well as frequent comorbidities, such as joint hypermobility, anxiety, and gastrointestinal issues. The medical management of OI is considered, which includes both nonpharmacologic and pharmacologic approaches. Finally, we discuss the prognosis and long-term implications of OI and indicate future directions for research and patient management.

Syncope in Young Women: Broadening the Differential Diagnosis.

Syncope is defined as a sudden transient loss of consciousness (TLOC) with concomitant loss of postural tone followed by spontaneous recovery. It is a subset of a broader class of medical conditions, including postural orthostatic tachycardia syndrome (POTS), orthostatic hypotension, and neurally mediated syncope (NMS), that may result in TLOC. The overlap of these clinical conditions leads to confusion regarding syncope classification that can hinder evaluation strategies, and pose challenges for diagnosis and treatment, particularly in young women. In this article, we review POTS, orthostatic hypotension, and NMS with an emphasis on NMS. These diverse orthostatic clinical entities may be associated with syncope and are frequently observed in young, healthy women. The importance of considering NMS as a diagnosis of exclusion cannot be overstated. We report a series of three young, otherwise healthy women, initially diagnosed with NMS, whose clinical course evolved over time into more sinister diagnoses that were overlooked and associated with devastating clinical outcomes. These cases highlight the importance of maintaining a broad differential diagnosis when considering the diagnosis of NMS. Each case synopsis provides key clinical features that must be considered to avoid overlooking more serious clinical conditions.

Human Papillomavirus Vaccine and Postural Orthostatic Tachycardia Syndrome: A Review of Current Literature.

The human papillomavirus (HPV) vaccine is efficacious in preventing complications of human papillomavirus infection including cervical cancer. However, there have been case reports of adverse events occurring after vaccination, one being postural orthostatic tachycardia syndrome (POTS). This article reviews published data and other available information regarding the relationship between the human papillomavirus vaccine and POTS. Background information is provided regarding the human papillomavirus vaccine and the proposed post-vaccination adverse event POTS. Peer-reviewed literature, statements by government and medical advisory committees, and publicly available information published on this topic are examined. At this time, there is no conclusive evidence supporting a causal relationship between the human papillomavirus vaccine and POTS. Though a causal relationship has been postulated, it is of utmost importance to recognize that while temporal associations may be observed, conclusions of causality cannot be drawn from case reports and case series due to the small sample size and lack of control population.

Possible adverse effects of the quadrivalent human papillomavirus vaccine in the Region of Southern Denmark: a retrospective, descriptive cohort study.

INTRODUCTION: Since the introduction of the quadrivalent human papillomavirus vaccine, young girls and women have reported a broad range of symptoms. These have been described as possible adverse effects of the vaccine. In this study, we describe demographic characteristics, symptomatology, clinical and laboratory test results in patients referred with suspected adverse effects in the Region of Southern Denmark. METHODS: We conducted a retrospective, descriptive study. The patients filled out a questionnaire, were interviewed by a doctor and received a standard physical examination and laboratory tests. RESULTS: The study comprised 200 patients. The median age at referral was 22 (interquartile range (IQR): 19.5-26) years, and age at first vaccination was 14 (IQR: 12-21) years. The most common symptoms were headache (93%), fatigue/tiredness (93%) and dizziness when standing up (90%). The median number of symptoms in each patient was 15. Five patients (2.5%) were diagnosed with postural orthostatic tachycardia syndrome (POTS). Of all patients, 183 (91.5%) were terminated without a somatic diagnosis, one patient (0.5%) was terminated with a functional disorder and 11 patients (5.5%) were still in diagnostic workup when the present study concluded. CONCLUSIONS: The patients reported a wide range of symptoms. We found an overall low prevalence of POTS. It should be further investigated whether these patients might suffer from a functional disorder rather than from adverse effects associated with the vaccine. FUNDING: none. TRIAL REGISTRATION: not relevant.

Postural orthostatic tachycardia is not a useful diagnostic marker for chronic fatigue syndrome.

BACKGROUND: Postural orthostatic tachycardia syndrome (POTS) is considered a diagnostic marker for chronic fatigue syndrome (CFS). OBJECTIVES: The aims of this study were to (i) compare POTS prevalence in a CFS cohort with fatigued patients not meeting CFS criteria, and (ii) assess activity, impairment and response to cognitive behavioural therapy (CBT) in CFS patients with POTS (POTS-CFS) and without POTS (non-POTS-CFS). METHODS: Prospective cohort study at the Radboud University Medical Centre in the Netherlands. Between June 2013 and December 2014, 863 consecutive patients with persistent fatigue were screened. Patients underwent an active standing test, filled out questionnaires and wore an activity-sensing device for a period of 12 days. RESULTS: A total of 419 patients with CFS and 341 non-CFS fatigued patients were included in the study. POTS prevalence in adult patients with CFS was 5.7% vs. 6.9% in non-CFS adults (P = 0.54). In adolescents, prevalence rates were 18.2% and 17.4%, respectively (P = 0.93). Adult patients with POTS-CFS were younger (30 ± 12 vs. 40 ± 13 years, P = 0.001) and had a higher supine heart rate (71 ± 11 vs. 65 ± 9 beats per min, P = 0.009) compared with non-POTS-CFS patients. Severity and activity patterns did not differ between groups. In patients with CFS, criteria for Systemic Exertion Intolerance Disease (SEID) were met in 76% of adults and 67% of adolescents. In these patients with CFS fulfilling the SEID criteria, the prevalence of POTS was not different from that in the overall CFS population. POTS-CFS adolescents had less clinically significant improvement after CBT than non-POTS-CFS adolescents (58% vs. 88%, P = 0.017). CONCLUSION: In adults with CFS, the prevalence of POTS was low, was not different from the rate in non-CFS fatigued patients and was not related to disease severity or treatment outcome. In POTS-CFS adolescents, CBT was less successful than in non-POTS-CFS patients. The evaluation of POTS appears to be of limited value for the diagnosis of CFS.