Autonomic dysfunction presenting as orthostatic intolerance in patients suffering from mitochondrial cytopathy

Cardiovascular autonomic reflex tests and serum FGF21 levels in overweight and normal-weight men and women

OBJECTIVE

We evaluated cardiovascular autonomic reflexes and serum fibroblast growth factor 21 (FGF21), a surrogate marker of mitochondrial function, in a cohort of overweight and normal-weight adults (n = 42).

METHODS

Indices of autonomic function were monitored during supine rest, autonomic reflex tests and submaximal clinical exercise test, with heart rate variables and blood pressure measured with an automatic system.

RESULTS

Markers of sympathetic dominance were accentuated in overweight adults, including elevated resting low-frequency to the high-frequency ratio for heart rate variability (203 ± 227 vs. 96 ± 42; p = .01), and handgrip diastolic blood pressure (36 ± 15 mmHg vs. 25 ± 12 mmHg; p = .01). A weak non-significant trend has been found for a negative correlation between blood pressure responses to isometric handgrip test and FGF21 in the overweight group (r = -0.37; p = .09).

CONCLUSIONS

Excess body weight appears to trigger sympathetic overactivity in overweight adults, yet autonomic dysregulation might not be associated with notable changes in serum FGF21.

When POTS is the tip of the iceberg: Rare cases of dysautonomia as a possible manifestation of another disorder

BACKGROUND

Postural tachycardia syndrome (POTS) is a heterogenous disorder of the autonomic nervous system that is commonly associated with small fiber neuropathy, Ehlers-Danlos Syndrome and autoimmune disorders, but association with rare conditions may also occur.

METHODS

Reported here are clinical features, diagnostic tests and treatment outcomes of 6 unique patients who presented with POTS and were subsequently diagnosed with Fabry disease, McArdle disease, Complex V mitochondrial disease, carcinoid tumor, Hodgkin's lymphoma and chemotherapy-induced neuropathy.

RESULTS

All patients (age range 15-57 years, 3 females, 3 males) presented with orthostatic intolerance of at least 6 months duration, and all patients had co-morbid small fiber neuropathy. Five patients presented with symptoms of POTS months to years before the underlying or associated medical condition was discovered, and three out of six patients experienced either complete resolution or significant improvement of POTS after treatment of the underlying or associated medical condition.

CONCLUSION

In rare cases, POTS can present as a possible manifestation of genetic, neoplastic or neurotoxic disorders. Unusual clinical features that fall outside of the typical spectrum of dysautonomia can point toward the presence of another disorder and help guide further diagnostic investigation.

Myalgic encephalomyelitis/chronic fatigue syndrome: From pathophysiological insights to novel therapeutic opportunities

Myalgic encephalomyelitis (ME) or chronic fatigue syndrome (CFS) is a common and disabling condition with a paucity of effective and evidence-based therapies, reflecting a major unmet need. Cognitive behavioural therapy and graded exercise are of modest benefit for only some ME/CFS patients, and many sufferers report aggravation of symptoms of fatigue with exercise. The presence of a multiplicity of pathophysiological abnormalities in at least the subgroup of people with ME/CFS diagnosed with the current international consensus "Fukuda" criteria, points to numerous potential therapeutic targets. Such abnormalities include extensive data showing that at least a subgroup has a pro-inflammatory state, increased oxidative and nitrosative stress, disruption of gut mucosal barriers and mitochondrial dysfunction together with dysregulated bioenergetics. In this paper, these pathways are summarised, and data regarding promising therapeutic options that target these pathways are highlighted; they include coenzyme Q₁₀, melatonin, curcumin, molecular hydrogen and N-acetylcysteine. These data are promising yet preliminary, suggesting hopeful avenues to address this major unmet burden of illness.

Myalgic encephalomyelitis or chronic fatigue syndrome: how could the illness develop?

A model of the development and progression of chronic fatigue syndrome (myalgic encephalomyelitis), the aetiology of which is currently unknown, is put forward, starting with a consideration of the post-infection role of damage-associated molecular patterns and the development of chronic inflammatory, oxidative and nitrosative stress in genetically predisposed individuals. The consequences are detailed, including the role of increased intestinal permeability and the translocation of commensal antigens into the circulation, and the development of dysautonomia, neuroinflammation, and neurocognitive and neuroimaging abnormalities. Increasing levels of such stress and the switch to immune and metabolic downregulation are detailed next in relation to the advent of hypernitrosylation, impaired mitochondrial performance, immune suppression, cellular hibernation, endotoxin tolerance and sirtuin 1 activation. The role of chronic stress and the development of endotoxin tolerance via indoleamine 2,3-dioxygenase upregulation and the characteristics of neutrophils, monocytes, macrophages and T cells, including regulatory T cells, in endotoxin tolerance are detailed next. Finally, it is shown how the immune and metabolic abnormalities of chronic fatigue syndrome can be explained by endotoxin tolerance, thus completing the model.

The patient perspective: What postural orthostatic tachycardia syndrome patients want physicians to know

Diagnosing and treating postural orthostatic tachycardia syndrome (POTS) can be a frustrating experience for patients and physicians alike. Experienced patient leaders solicited input from the large online POTS community to identify patient suggestions and concerns, with the goal of improving the patient-physician relationship and outcomes in POTS. This review article offers practical tips to improve POTS patient care and links to credible resources for your patients. The authors emphasize the urgent need for improved physician education, a tailored treatment approach, and expanded research efforts.

Recognizing postural orthostatic tachycardia syndrome

This article describes the pathophysiology, clinical presentation, differential diagnosis, diagnosis, and management of postural orthostatic tachycardia syndrome (POTS), a potentially debilitating autonomic disorder that can have many causes and presentations. POTS can be mistaken for panic disorder, inappropriate sinus tachycardia, and chronic fatigue syndrome. Clinician suspicion for the syndrome is key to prompt patient diagnosis and treatment.

A critical analysis of the proposal of the Institute of Medicine to replace myalgic encephalomyelitis and chronic fatigue syndrome by a new diagnostic entity called systemic exertion intolerance disease

The Institute of Medicine (IOM) recently published their report in response to an assignment "to define diagnostic criteria for Myalgic Encephalomyelitis (ME)/chronic fatigue syndrome (CFS), to propose a process for reevaluation of these criteria in the future, and to consider whether a new name for this disease is warranted". The basic pre-assumption of the IOM committee for the development of evidence-based diagnostic criteria for ME/CFS was that ME and CFS denote conditions with similar symptoms, hence ME/CFS. The IOM committee recommends: (1) that ME/CFS will be renamed 'systemic exertion intolerance disease' (SEID); and that a new code should be assigned to SEID in the International Classification of Diseases (ICD), replacing the existing codes for ME (a neurological disease: G93.3) and CFS ('signs, symptoms, and abnormal clinical and laboratory findings, not elsewhere classified': R53.82); (2) that a diagnosis of SEID should be made if the new diagnostic criteria are met; (3) that the Department of Health and Human Services develops a toolkit appropriate for screening and diagnosing patients; and (4) that a multidisciplinary group re-examines the new diagnostic criteria when necessary. This editorial reviews the working procedure of the IOM and two of the outcomes: the recommendation to introduce a new clinical entity (SEID) and new diagnostic criteria. Based upon the contents of the report, and the arguments of the IOM, a search of PubMed and the archive of the Journal of Chronic Fatigue Syndrome using the search terms ME (and old synonyms) and CFS, and a search of PubMed related to the five core symptoms of SEID was conducted. Reviewing the working method and the recommendations, it is concluded that the new diagnostic criteria for SEID are based upon important methodological shortcomings and that the introduction of SEID to replace both ME and CFS has several profound negative consequences outweighing the advantages.

Cardiac manifestations of primary mitochondrial disorders

OBJECTIVES

One of the most frequently affected organs in mitochondrial disorders (MIDs), defined as hereditary diseases due to affection of the mitochondrial energy metabolism, is the heart. Cardiac involvement (CI) in MIDs has therapeutic and prognostic implications. This review aims at summarizing and discussing the various cardiac manifestations in MIDs.

METHODS

Data for this review were identified by searches of MEDLINE, Current Contents, and PubMed using appropriate search terms.

RESULTS

CI in MIDs may be classified according to various different criteria. In the present review cardiac abnormalities in MIDs are discussed according to their frequency with which they occur. CI in MIDs includes cardiomyopathy, arrhythmias, heart failure, pulmonary hypertension, dilation of the aortic root, pericardial effusion, coronary heart disease, autonomous nervous system dysfunction, congenital heart defects, or sudden cardiac death. The most frequent among the cardiomyopathies is hypertrophic cardiomyopathy, followed by dilated cardiomyopathy, and noncompaction.

CONCLUSIONS

CI in MID is more variable and prevalent than previously thought. All tissues of the heart may be variably affected. The most frequently affected tissue is the myocardium. MIDs should be included in the differential diagnoses of cardiac disease.

Presumed mitochondrial disease manifesting with recurrent syncopes

OBJECTIVES

Loss of consciousness may be due to neurological or cardiac involvement in mitochondrial disease, and is often difficult to attribute to either cause, as in the following case.

CASE REPORT

A 67-year-old man with hypertension, diabetes, elevated serum creatine kinase, glaucoma, optic atrophy, and vertigo had experienced recurrent losses of consciousness since 63 years of age. Diagnostic work-up revealed paroxysmal supraventricular arrhythmias, hyperlipidemia, steatosis hepatis, renal insufficiency, polyneuropathy, first-degree atrio-ventricular block, orthostasis, and cataract. From the age of 66 years, he developed tonic-clonic seizures. Electrocardiography loop recording showed some losses of consciousness as associated with supraventricular tachycardias and others with epileptic activity or arterial hypotension. Neurological investigations and muscle biopsy were indicative of mitochondrial disease with multisystem involvement. Losses of consciousness disappeared after catheter ablation and treatment with levetiracetam.

CONCLUSION

Recurrent loss of consciousness in mitochondrial disease may not only be due to arrhythmias but also seizure activity, or autonomic neuropathy. Arrhythmias, seizures, and polyneuropathy may have a common underlying cause affecting various tissues.

Intranuclear rods myopathy with autonomic dysfunction

Intranuclear rods myopathy (IRM), a variant of nemaline myopathy (NM), is characterized by rod structure in the myonuclei. Patients with IRM present with similar symptoms to those of severe infantile-type NM but have worse outcome. Several extramuscular manifestations have been reported in NM but no dysautonomia. We herein report a 2-year-old girl with IRM and a heterozygous mutation, c.430C>T (p.L144F) in ACTA1. During the infancy, the patient showed severe diaphoresis and facial flushing. Arrhythmia and hypertension with the precipitating factors of feeding, defecation, and urination were observed. Sympathetic antagonist was prescribed and showed some effectiveness. Our report may widen the clinical spectrum of IRM. It also reminds clinicians that autonomic dysfunction may occur in patients with IRM or other actinopathies and appropriate treatment may be necessary.

Mitochondrial disease in childhood: nuclear encoded

Primary mitochondrial disorders are clinically and genetically heterogeneous, caused by an alteration(s) in either mitochondrial DNA or nuclear DNA, and affect the respiratory chain's ability to undergo oxidative phosphorylation, leading to decreased production of adenosine triphosphophate and subsequent energy failure. These disorders may present at any age, but children tend to have an acute onset of disease compared with subacute or slowly progressive presentation in adults. Varying organ involvement also contributes to the phenotypic spectrum seen in these disorders. The childhood presentation of primary mitochondrial disease is mainly due to nuclear DNA mutations, with mitochondrial DNA mutations being less frequent in childhood and more prominent in adulthood disease. The clinician should be aware of the pediatric presentation of mitochondrial disease and have an understanding of the myriad of nuclear genes responsible for these disorders. The nuclear genes can be best understood by utilizing a classification system of location and function within the mitochondria.

Autonomic dysfunction in epilepsy and mitochondrial diseases

The autonomic nervous system is involved and influenced in patients with epilepsy and mitochondrial diseases in a variety of complex, often multifaceted, mechanisms. Autonomic dysfunction often remains unrecognized due to a lack of attention and awareness under the prominence of other disease symptoms. Recognition of the diverse autonomic manifestations of epilepsy and mitochondrial disease would enhance early diagnosis and appropriate management, ultimately improving quality the of life and reducing morbidity and mortality in the affected patients. In this chapter, we discuss autonomic nervous system dysfunction in children with epilepsy (Part I) and mitochondrial diseases (Part II).