Lumping or splitting? "Ophthalmoplegia-plus" or Kearns-Sayre syndrome?

Overlap between ophthalmology and psychiatry - A narrative review focused on congenital and inherited conditions

A number of congenital and inherited diseases present with both ocular and psychiatric features. The genetic inheritance and phenotypic variants play a key role in disease severity. Early recognition of the signs and symptoms of those disorders is critical to earlier intervention and improved prognosis. Typically, the associations between these two medical subspecialties of ophthalmology and psychiatry are poorly understood by most practitioners so we hope to provide a narrative review to improve the identification and management of these disorders. We conducted a comprehensive review of the literature detailing the diseases with ophthalmic and psychiatric overlap that were more widely represented in the literature. Herein, we describe the clinical features, pathophysiology, molecular biology, diagnostic tests, and the most recent approaches for the treatment of these diseases. Recent studies have combined technologies for ocular and brain imaging such as optical coherence tomography (OCT) and functional imaging with genetic testing to identify the genetic basis for eye-brain connections. Additional work is needed to further explore these potential biomarkers. Overall, accurate, efficient, widely distributed and non-invasive tests that can help with early recognition of these diseases will improve the management of these patients using a multidisciplinary approach.

Progressive external ophthalmoplegia

Progressive external ophthalmoplegia (PEO), characterized by ptosis and impaired eye movements, is a clinical syndrome with an expanding number of etiologically distinct subtypes. Advances in molecular genetics have revealed numerous pathogenic causes of PEO, originally heralded in 1988 by the detection of single large-scale deletions of mitochondrial DNA (mtDNA) in skeletal muscle of people with PEO and Kearns-Sayre syndrome. Since then, multiple point variants of mtDNA and nuclear genes have been identified to cause mitochondrial PEO and PEO-plus syndromes, including mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) and sensory ataxic neuropathy dysarthria ophthalmoplegia (SANDO). Intriguingly, many of those nuclear DNA pathogenic variants impair maintenance of the mitochondrial genome causing downstream mtDNA multiple deletions and depletion. In addition, numerous genetic causes of nonmitochondrial PEO have been identified.

[Chronic progressive external ophthalmoplegia that could not be diagnosed by biceps muscle biopsy, but was genetically diagnosed by extraocular muscle biopsy]

A 48-year-old Japanese male experienced slowly progressive diplopia. He had no family history and was negative for the edrophonium chloride test. Blood analysis showed elevated lactic acid and pyruvic acid levels, suggesting mitochondrial disease. A muscle biopsy from the biceps brachii was performed, but no pathological or genetical mitochondrial abnormalities were detected. Subsequently, he underwent muscle plication for diplopia in which the right inferior rectus muscle was biopsied. Genetic examination of genomic DNA extracted from the extraocular muscle tissue revealed multiple mitochondrial gene deletions, with a heteroplasmy rate of approximately 35%, resulting in the diagnosis of chronic progressive external ophthalmoplegia. In mitochondrial diseases, the tissue distribution of mitochondria with disease-associated variants in mtDNA should be noted, and it is important to select the affected muscle when performing a biopsy for an accurate diagnosis.

Cardiomyopathies in Children and Systemic Disorders When Is It Useful to Look beyond the Heart?

Cardiomyopathy (CMP) is a rare disease in the pediatric population, with a high risk of morbidity and mortality. The genetic etiology of CMPs in children is extremely heterogenous. These two factors play a major role in the difficulties of establishing standard diagnostic and therapeutic protocols. Isolated CMP in children is a frequent finding, mainly caused by sarcomeric gene variants with a detection rate that can reach up to 50% of analyzed cohorts. Complex multisystemic forms of pediatric CMP are even more heterogenous. Few studies in literature take into consideration this topic as the main core since it represents a rarity (systemic CMP) within a rarity (pediatric population CMP). Identifying etiology in this cohort is essential for understanding prognosis, risk stratification, eligibility to heart transplantation and/or mechanical-assisted procedures, preventing multiorgan complications, and relatives' recurrence risk calculation. The previous points represent a cornerstone in patients' empowerment and personalized medical care approach. The aim of this work is to propose a new approach for an algorithm in the setting of the diagnostic framework of systemic pediatric CMP. On the other hand, during the literature review, we noticed a relatively common etiologic pattern in some forms of complex/multisystem CMP. In other words, certain syndromes such as Danon, Vici, Alström, Barth, and Myhre syndrome share a common pathway of directly or indirectly defective "autophagy" process, which appears to be a possible initiating/triggering factor for CMPs. This conjoint aspect could be important for possible prognostic/therapeutic implications in this category of patients. However, multicentric studies detailed functional and experimental models are needed prior to deriving conclusions.

Myocardial and Arrhythmic Spectrum of Neuromuscular Disorders in Children

Neuromuscular disorders (NMDs) are highly heterogenous from both an etiological and clinical point of view. Their signs and symptoms are often multisystemic, with frequent cardiac involvement. In fact, childhood onset forms can predispose a person to various progressive cardiac abnormalities including cardiomyopathies (CMPs), valvulopathies, atrioventricular conduction defects (AVCD), supraventricular tachycardia (SVT) and ventricular arrhythmias (VA). In this review, we selected and described five specific NMDs: Friedreich's Ataxia (FRDA), congenital and childhood forms of Myotonic Dystrophy type 1 (DM1), Kearns Sayre Syndrome (KSS), Ryanodine receptor type 1-related myopathies (RYR1-RM) and Laminopathies. These changes are widely investigated in adults but less researched in children. We focused on these specific topics due their relative frequency and their potential unexpected cardiac manifestations in children. Moreover these conditions present different inheritance patterns and mechanisms of action. We decided not to discuss Duchenne and Becker muscular dystrophies due to extensive work regarding the cardiac aspects in children. For each described NMD, we focused on the possible cardiac manifestations such as different types of CMPs (dilated-DCM, hypertrophic-HCM, restrictive-RCM or left ventricular non compaction-LVNC), structural heart abnormalities (including valvulopathies), and progressive heart rhythm changes (AVCD, SVT, VA). We describe the current management strategies for these conditions. We underline the importance, especially for children, of a serial multidisciplinary personalized approach and the need for periodic surveillance by a dedicated heart team. This is largely due to the fact that in children, the diagnosis of certain NMDs might be overlooked and the cardiac aspect can provide signs of their presence even prior to overt neurological diagnosis.

Progressive involvement of cardiac conduction system in paediatric patients with Kearns-Sayre syndrome: how to predict occurrence of complete heart block and sudden cardiac death?

AIMS

The aims of this study are to evaluate the progressive involvement of the cardiac conduction system in the Kearn-Sayre syndrome (KSS) and to establish criteria for the prevention of episodes of syncope or sudden cardiac death.

METHODS AND RESULTS

This is a prospective monocentric study including KSS patients, with diagnosis based on clinical manifestations, muscle biopsy, and genetic tests, before the age of 18. All patients underwent cardiac screening examination with 12-lead electrocardiogram (ECG), 24-h Holter monitoring, and pacemaker (PM) interrogation twice a year. Fifteen patients (nine males, mean age 16.6 ± 3.9 years) with a sporadic KSS were recruited. All subjects manifested at least one of the intraventricular conduction defects (IVDs): 1 right bundle branch block (RBBB), 2 left anterior fascicular block (LAFB), 11 a bi-fascicular block (RBBB + LAFB), and 1 left posterior fascicular block. Most children with bi-fascicular block developed LAFB before the RBBB (P = 0.0049). In six patients, IVD degenerated into atrioventricular block (AVB). Endocavitary PM was implanted in 11 patients (6 with AVB and 5 with a bi-fascicular block), while an implantable cardioverter-defibrillator only in one patient with a non-sustained ventricular tachycardia. Four died at mean age of 14.7 ± 2.6 years, but none of them suddenly.

CONCLUSION

Even a 'simple' ECG can predict the arrhythmic risk and the occurrence of catastrophic events in young patients with KSS. Left anterior fascicular block precedes RBBB in determining the bi-fascicular block and this can predict an inexorable progression of the conduction defects even in a short time. Pacemaker implantation may be indicated in these patients since the first bi-fascicular block manifestation.

Retinoschisis associated with Kearns-Sayre syndrome

Background:

Kearns-Sayre Syndrome (KSS) is characterized by pigmentary retinopathy, external ophthalmoplegia and heart block. We report on a now 24-year-old male with clinical retinoschisis and molecularly confirmed KSS.

Materials and Methods:

Physical and complete ophthalmic examination, molecular diagnosis.

Results:

Over nine years of follow-up, the subject manifested progressive signs and symptoms of KSS, including external ophthalmoplegia/strabismus, ptosis, pigmentary retinopathy, corneal edema, Type I diabetes mellitus, gut dysmotility, sensorineural deafness and heart block. At age 21 he was incidentally found to have retinoschisis on optical coherence tomography that remained stable over three years follow-up. Sequencing of the RS1 gene revealed no pathogenic variants, effectively ruling out co-existing X-linked retinoschisis.

Conclusions:

These findings suggest retinoschisis may be a rare manifestation of KSS. A trial of a carbonic anhydrase inhibitor was frustrated by coexisting corneal edema associated with the condition.

Mitochondrial disease in children

Mitochondrial disease presenting in childhood is characterized by clinical, biochemical and genetic complexity. Some children are affected by canonical syndromes, but the majority have nonclassical multisystemic disease presentations involving virtually any organ in the body. Each child has a unique constellation of clinical features and disease trajectory, leading to enormous challenges in diagnosis and management of these heterogeneous disorders. This review discusses the classical mitochondrial syndromes presenting most frequently in childhood and then presents an organ-based perspective including systems less frequently linked to mitochondrial disease, such as skin and hair abnormalities and immune dysfunction. An approach to diagnosis is then presented, encompassing clinical evaluation and biochemical, neuroimaging and genetic investigations, and emphasizing the problem of phenocopies. The impact of next-generation sequencing is discussed, together with the importance of functional validation of novel genetic variants never previously linked to mitochondrial disease. The review concludes with a brief discussion of currently available and emerging therapies. The field of mitochondrial medicine has made enormous strides in the last 30 years, with approaching 400 different genes across two genomes now linked to primary mitochondrial disease. However, many important questions remain unanswered, including the reasons for tissue specificity and variability of clinical presentation of individuals sharing identical gene defects, and a lack of disease-modifying therapies and biomarkers to monitor disease progression and/or response to treatment.

Mitochondrial disorders and the eye

Mitochondria are cellular organelles that play a key role in energy metabolism and oxidative phosphorylation. Malfunctioning of mitochondria has been implicated as the cause of many disorders with variable inheritance, heterogeneity of systems involved, and varied phenotype. Metabolically active tissues are more likely to be affected, causing an anatomic and physiologic disconnect in the treating physicians' mind between presentation and underlying pathophysiology. We shall focus on disorders of mitochondrial metabolism relevant to an ophthalmologist. These disorders can affect all parts of the visual pathway (crystalline lens, extraocular muscles, retina, optic nerve, and retrochiasm). After the introduction reviewing mitochondrial structure and function, each disorder is reviewed in detail, including approaches to its diagnosis and most current management guidelines.

Combination of microdissection and single cell quantitative real-time PCR revealed intercellular mitochondrial DNA heterogeneities in fibroblasts of Kearns-Sayre syndrome patients

Kearns-Sayre syndrome (KSS) is a multisystemic disorder marked by aerobic cell metabolism dysfunction. Fibroblasts derived from KSS patient skin biopsy exhibit heterogeneous occurrence of mitochondrial genomes as those circular DNA molecules partially carry the common deletion. In our approach, we aim to evaluate the intercellular alterations in respect to mitochondrial DNA integrity by laser capture microdissection and multiplex quantitative real-time PCR in single cells. The obtained results give new insights into the understanding of mitochondrial genetics, e.g. postulated sorting of damaged mitochondria, and heterogeneity of cells. Further, we discuss the relevance of intercellular heterogeneities for human mitochondrial disorders in general.

Clinical syndromes associated with mtDNA mutations: where we stand after 30 years

The landmark year 1988 can be considered as the birthdate of mitochondrial medicine, when the first pathogenic mutations affecting mtDNA were associated with human diseases. Three decades later, the field still expands and we are not ‘scraping the bottom of the barrel’ yet. Despite the tremendous progress in terms of molecular characterization and genotype/phenotype correlations, for the vast majority of cases we still lack a deep understanding of the pathogenesis, good models to study, and effective therapeutic options. However, recent technological advances including somatic cell reprogramming to induced pluripotent stem cells (iPSCs), organoid technology, and tailored endonucleases provide unprecedented opportunities to fill these gaps, casting hope to soon cure the major primary mitochondrial phenotypes reviewed here. This group of rare diseases represents a key model for tackling the pathogenic mechanisms involving mitochondrial biology relevant to much more common disorders that affect our currently ageing population, such as diabetes and metabolic syndrome, neurodegenerative and inflammatory disorders, and cancer.

Kearns-Sayre Syndrome: A Case Report and Review

In 1958, Kearns and Sayre described a multisystem entity, now known as Kearns-Sayre syndrome (KSS). The syndrome is defined as exhibiting a triad of thus far unexplained degenerative conditions: progressive external ophthalmoplegia, retinal pigmentary degeneration, and heart block. Commonly accompanying findings include cerebellar dysfunction and CSF protein levels above 100 mg/dl. Symptoms usually appear in early childhood, but the onset has been seen occasionally in young adults. KSS is a mitochondrial disorder that occurs rarely; the actual incidence is unknown. Ocular findings consist of bilateral ptosis, chronic progressive external ophthalmoplegia, and pigmentary retinopathy. Corneal clouding and optic neuritis are infrequent.

We herein report a classic case of Kearns Sayre syndrome and discuss the findings.

Nerve excitability changes related to muscle weakness in chronic progressive external ophthalmoplegia

OBJECTIVE

To explore potential spreading to peripheral nerves of the mitochondrial dysfunction in chronic progressive external ophthalmoplegia (CPEO) by assessing axonal excitability.

METHODS

CPEO patients (n=13) with large size deletion of mitochondrial DNA and matching healthy controls (n=22) were included in a case-control study. Muscle strength was quantified using MRC sum-score and used to define two groups of patients: CPEO-weak and CPEO-normal (normal strength). Nerve excitability properties of median motor axons were assessed with the TROND protocol and changes interpreted with the aid of a model.

RESULTS

Alterations of nerve excitability strongly correlated with scores of muscle strength. CPEO-weak displayed abnormal nerve excitability compared to CPEO-normal and healthy controls, with increased superexcitability and responses to hyperpolarizing current. Modeling indicated that the CPEO-weak recordings were best explained by an increase in the 'Barrett-Barrett' conductance across the myelin sheath.

CONCLUSION

CPEO patients with skeletal weakness presented sub-clinical nerve excitability changes, which were not consistent with axonal membrane depolarization, but suggested Schwann cell involvement.

SIGNIFICANCE

This study provides new insights into the spreading of large size deletion of mitochondrial DNA to Schwann cells in CPEO patients.

Coenzyme Q10 in the Treatment of Corneal Edema in Kearns-Sayre: Is There an Application in Fuchs Endothelial Corneal Dystrophy?

PURPOSE

Corneal involvement in mitochondrial disease is seldom described. Kearns-Sayre syndrome (KSS) is a mitochondrial disorder characterized by retinitis pigmentosa, external ophthalmoplegia, and heart block. We report 2 patients with KSS with corneal lesions involving the endothelium, which improved with Coenzyme Q10 (CoQ10). Based on recent research regarding the role of dysfunctional oxidative metabolism in Fuchs Endothelial Corneal Dystrophy (FECD), we propose that mitochondrial diseases and FECD share a final pathway.

METHODS

A chart review was performed and a review of the literature was completed with a PubMed search using the terms "Kearns-Sayre Syndrome", "mitochondria", "endothelium", "Fuchs endothelial corneal dystrophy", and "cornea".

RESULTS

There are 19 reports of corneal involvement in clinical phenotypes of mitochondrial disease. Nine of these 19 cases had findings consistent with KSS. Our patients with KSS had microcystic changes throughout the cornea and excrescences on the endothelial surface seen with ultrasound biomicroscopy, similar to the clinical findings in FECD. CoQ10 improved corneal disease in both children. CoQ10 deficiency has been reported in a variety of mitochondrial diseases, and efficacy of supplementation has been demonstrated. It may be beneficial in these patients because of its antioxidant properties and role in oxidative phosphorylation.

CONCLUSIONS

The common deletion found in patients with KSS has recently been implicated in FECD, which has recently been shown to be a disease related to dysfunctional oxidative metabolism. Future research should explore the use of antioxidants, such as CoQ10 in patients with FECD.

Mitochondrial disease and endocrine dysfunction

Mitochondria are critical organelles for endocrine health; steroid hormone biosynthesis occurs in these organelles and they provide energy in the form of ATP for hormone production and trafficking. Mitochondrial diseases are multisystem disorders that feature defective oxidative phosphorylation, and are characterized by enormous clinical, biochemical and genetic heterogeneity. To date, mitochondrial diseases have been found to result from >250 monogenic defects encoded across two genomes: the nuclear genome and the ancient circular mitochondrial genome located within mitochondria themselves. Endocrine dysfunction is often observed in genetic mitochondrial diseases and reflects decreased intracellular production or extracellular secretion of hormones. Diabetes mellitus is the most frequently described endocrine disturbance in patients with inherited mitochondrial diseases, but other endocrine manifestations in these patients can include growth hormone deficiency, hypogonadism, adrenal dysfunction, hypoparathyroidism and thyroid disease. Although mitochondrial endocrine dysfunction frequently occurs in the context of multisystem disease, some mitochondrial disorders are characterized by isolated endocrine involvement. Furthermore, additional monogenic mitochondrial endocrine diseases are anticipated to be revealed by the application of genome-wide next-generation sequencing approaches in the future. Understanding the mitochondrial basis of endocrine disturbance is key to developing innovative therapies for patients with mitochondrial diseases.

Dilated cardiomyopathy with cardiogenic shock in a child with Kearns-Sayre syndrome

Kearns-Sayre syndrome (KSS) is a mitochondrial myopathy resulting from mitochondrial DNA deletion. This syndrome primarily involves the central nervous system, eyes, skeletal muscles and the heart. The most well-known cardiac complications involve the conduction system; however, there have been case reports describing cardiomyopathy. We describe a case of a child with KSS who presented with decompensated cardiac failure from dilated cardiomyopathy representing cardiomyocyte involvement of KSS. Our patient had a rapidly progressing course, despite maximal medical management, requiring emergent institution of extracorporeal membrane oxygenation and transition to a ventricular assist device. To the best of our knowledge, this is the youngest patient in the literature to have dilated cardiomyopathy in KSS.

Causes of Death in Adults with Mitochondrial Disease

INTRODUCTION

Mitochondrial diseases are a clinically, biochemically and genetically heterogeneous group of disorders with a variable age of onset and rate of disease progression. It might therefore be expected that this variation be reflected in the age and cause of death. However, to date, little has been reported regarding the 'end-of-life' period and causes of death in mitochondrial disease patients. For some specific syndromes, the associated clinical problems might predict the cause of death, but for many patients, it remains difficult to provide an accurate prognosis.

AIMS

To describe a retrospective cohort of adult mitochondrial disease patients who had attended the NHS Highly Specialised Services for Rare Mitochondrial Diseases in Newcastle upon Tyne (UK), evaluate life expectancy and causes of death and assess the consequences for daily patient care.

METHODS

All deceased adult patients cared for at this centre over a period of 10 years were included in the study. Patient history, data on laboratory findings, biochemical investigations and genetic studies were analysed retrospectively.

RESULTS

A total of 30 adult mitochondrial patients died within the time period of the study. The main mitochondrial disease-related causes of death in this patient cohort were respiratory failure, cardiac failure and acute cerebral incidents such as seizures and strokes. In almost half of the patients, the cause of death remained unknown. Based on our study, we present recommendations regarding the care of patients with mitochondrial disease.

Paediatric single mitochondrial DNA deletion disorders: an overlapping spectrum of disease

BACKGROUND

Single large-scale mitochondrial DNA (mtDNA) deletions (SLSMDs) are amongst the most frequently diagnosed mtDNA disorders in childhood, yet their natural history remains poorly understood. We report the natural history of a large multicentre cohort of such children.

METHODS

We reviewed case notes from three different UK centres to determine the clinical course of 34 patients (16 female, 18 male) with childhood-onset mitochondrial disease caused by SLSMDs. Kaplan-Meier analysis was used to compare survival of patients presenting with haematological features (Pearson syndrome) and those with nonhaematological presentations.

RESULTS

The most frequent initial presentation was with isolated ptosis (16/34, 47%). Eleven (32%) patients presented with transfusion-dependent anaemia soon after birth and were diagnosed with Pearson syndrome, whilst ten were classified as having Kearns-Sayre syndrome, three as having progressive external ophthalmoplegia (PEO) and seven as having PEO-plus. Three patients did not conform to any specific mitochondrial syndrome. The most frequently affected organ during the disease course was the kidney, with documented tubular or glomerular dysfunction in 17 of 20 (85%) cases who had detailed investigations. SLSMDs were present in blood and/or urine cells in all cases tested, indicating that muscle biopsy is not necessary for diagnosis in the paediatric age range. Kaplan-Meier survival analysis revealed significantly worse mortality in patients with Pearson syndrome compared with the rest of the cohort.

CONCLUSIONS

Mitochondrial disease caused by SLSMDs is clinically heterogeneous, and not all cases conform to a classical mitochondrial syndrome. Multisystem disease is the norm, with anaemia, renal impairment and endocrine disturbance being the most frequent extraneurological features. SLSMDs should be considered in the differential diagnosis of all children presenting with ptosis.

Cardiovascular manifestations of neurologic disease

Cardiac manifestations of neurologic diseases are common in clinical practice. There are numerous anatomic and pathophysiologic links between the normal and abnormal function of both systems. There are a number of brain-heart interactions which affect the care of patients as well as help guide therapeutic development. This is exemplified in the area of vascular neurology where knowledge of the brain-heart connection is essential not only for bedside management but where collaborative efforts between neurology and cardiology are key in developing new strategies for ischemic stroke prevention and treatment, atrial fibrillation, and interventional techniques. This chapter will focus on cardiac manifestations of neurologic disease, with special emphasis on vascular and intensive care neurology, epilepsy, and neurodegenerative and peripheral nervous system diseases.

Natural history of conduction abnormalities in a patient with Kearns-Sayre syndrome

Kearns-Sayre syndrome is a rare mitochondrial disorder characterized by large-scale deletion or rearrangement of mitochondrial DNA, which is usually not inherited but occur spontaneously probably at the germ cell level or very early in embryonic development by Mehndiratta et al. (Neurol India 50:162-167, 2002). Neuromuscular and cardiac conduction abnormalities are most commonly involved in these patients, which may have subtle presenting signs.

A novel mitochondrial DNA deletion in a patient with Kearns-Sayre syndrome: a late-onset of the fatal cardiac conduction deficit and cardiomyopathy accompanying long-term rGH treatment

Background

Kearns-Sayre Syndrome (KSS) is a multisystem disorder caused by a dysfunction of the oxidative phosphorylation system within mitochondria. Mitochondrial DNA (mtDNA) rearrangements are a key molecular feature of this disease, which manifest a broad phenotypic spectrum.

Case presentation

Here, we present a boy with KSS whose symptoms included cardiac conduction deficit, cardiomyopathy and growth hormone (GH) deficiency. The patient showed typical symptoms for KSS from early childhood (chronic progressive external ophthalmoplegia, retinopathy, short stature). Long-range PCR analysis disclosed a 7663-base pair heteroplasmic deletion in the mtDNA encompassing nucleotides 6340–14003. At 12 years of age, GH deficiency was recognized and recombinant growth hormone (rGH) therapy was started. At 15 years of age, a complete atrioventicular block was diagnosed and the patient received a pacemaker. During the following 6 months, progressive deterioration of the left ventricle was observed and an echocardiogram showed features of dilated cardiomyopathy. The rGH treatment was then discontinued at a final height of 163 cm. Unfortunately, due to multi-organ insufficiency and inflammation, the patient died at the age of 18 years.

Conclusions

The response to rGH therapy in the patient was very satisfactory. The large mtDNA deletion had no apparent impact on the response to rGH. Cardiac disturbances occurred as part of the syndrome and were not related to rGH therapy; however, the progression of the disease led to death.

Neurologic disorders due to mitochondrial DNA mutations

The mitochondrial DNA (mtDNA) is a compact genome inherited through the maternal lineage. Mutations in mtDNA lead to many of the earliest identified syndromic mitochondrial diseases and display a diverse range of age of onset, symptoms, and outcomes-from isolated childhood onset vision or hearing loss to a multisystemic neurodegenerative disorder with strokes, neuropathy, ophthalmoparesis, and epilepsy beginning at any age. As a heterogeneous group, mitochondrial diseases represent one of the most common metabolic disorders in children and adults, frequently seen by both pediatric and adult specialists. Although the myriad of diseases can make diagnosis seems daunting, the need for extensive supportive care and treatment (the latter for at least a select few mitochondrial disorders) and a rapid and accurate recognition of these disorders is necessary. Here, we provide a review of the most common mitochondrial disease syndromes due to mtDNA mutations.

Kearns Sayre Syndrome--case report with review of literature

Kearns-Sayre Syndrome is form of rare mitochondrial cytopathy, first described by Thomas P. Kearns and George Pomeroy Sayre in 1958 and is characterized by progressive external opthalmoplegia, cardiac conduction block, pigmentary retinal degeneration, variable number of red ragged fibers on muscle biopsy. It presents before the child reaches the age of twenty. Kearns-Sayre syndrome may affect many organ systems and additional features may include myopathy, dystonia, bulbar symptoms in the form of dysarthria and nasal regurgitation and bilateral facial weakness. Endocrine abnormalities (e.g., diabetes, growth retardation/short stature, and hypoparathyroidism), bilateral sensorineural deafness, dementia, cataracts, and proximal renal tubular acidosis, skeletal muscle weakness (proximal more than distal) and exercise intolerance are additional features. Kearns Sayre Syndrome occurs as a result of large-scale single deletions (or rearrangements) of mitochondrial DNA (mtDNA), which is usually not inherited but occurs spontaneously, probably at the germ-cell level or very early in embryonic development. No disease-modifying therapy is available for Kearns-Sayre syndrome (KSS). Management is supportive vigilance for detection of associated problems. In the future, potential treatment in patients with Kearns-Sayre syndrome may attempt to inhibit mutant mtDNA replication or encourage replication of wild-type mtDNA.

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

BACKGROUND

Disturbances in autonomic nervous system function have been reported to occur in patients suffering from mitochondrial cytopathies. However, there is paucity of literature on the occurrence of orthostatic intolerance (OI) in these patients. We report on a series of patients diagnosed with mitochondrial cytopathy who developed features of autonomic dysfunction in the form of OI.

METHODS

This was a single-center report on a series of 6 patients who were followed in our clinic for orthostatic intolerance. All of these patients had a diagnosis of mitochondrial cytopathy on the basis of muscle biopsy and were being followed at a center specializing in the treatment of mitochondrial disorders. This study was approved by our local institutional review board. Each of the patients had suffered from symptoms of fatigue, palpitations, near syncope, and syncope. The diagnosis of OI was confirmed by head-up tilt test. Collected data included demographic information, presenting symptoms, laboratory data, tilt-table response, and treatment outcomes.

RESULTS

Six patients (3 females) were identified for inclusion in this report. The mean age of the group was 48 ± 8 years (range, 40-60 years). All of these patients underwent head-up tilt table testing and all had a positive response that reproduced their clinical symptoms. Among those having an abnormal tilt-table pattern, 1 had a neurocardiogenic response, 1 had a dysautonomic response, and 4 had a postural orthostatic tachycardia response. All but 1 patient reported marked symptom relief with pharmacotherapy. The patient who failed pharmacotherapy received a dual-chamber closed-loop pacemaker and subsequently reported marked improvement in her symptoms with elimination of her syncope.

CONCLUSIONS

Orthostatic intolerance might be a significant feature of autonomic nervous system dysfunction in patients suffering from mitochondrial cytopathy.

[Neurology and cardiology: points of contact]

Strokes resulting from cardiac diseases, and cardiac abnormalities associated with neuromuscular disorders are examples of the many points of contact between neurology and cardiology. Approximately 20-30% of strokes are related to cardiac diseases, including atrial fibrillation, congestive heart failure, bacterial endocarditis, rheumatic and nonrheumatic valvular diseases, acute myocardial infarction with left ventricular thrombus, and cardiomyopathies associated with muscular dystrophies, among others. Strokes can also occur in the setting of cardiac interventions such as cardiac catheterization and coronary artery bypass procedures. Treatment to prevent recurrent stroke in any of these settings depends on the underlying etiology. Whereas anticoagulation with vitamin K antagonists is proven to be superior to acetylsalicylic acid for stroke prevention in atrial fibrillation, the superiority of anticoagulants has not been conclusively established for stroke associated with congestive heart failure and is contraindicated in those with infective endocarditis. Ongoing trials are evaluating management strategies in patients with atrial level shunts due to patent foramen ovale. Cardiomyopathies and conduction abnormalities are part of the spectrum of many neuromuscular disorders including mitochondrial disorders and muscular dystrophies. Cardiologists and neurologists share responsibility for caring for patients with or at risk for cardiogenic strokes, and for screening and managing the heart disease associated with neuromuscular disorders.

Progression of conduction system disease in a paced patient with Kearns-Sayre syndrome

The Kearns-Sayre syndrome is a rare condition characterized by external ophthalmoplegia, retinal pigmentary degeneration and progressive impairment of cardiac conduction. We report a patient with the permanent pacemaker. The spontaneous cardiac impulse formation disappeared during long-term follow-up in this patient with Kearns-Sayre Syndrome.

Rapid development of life-threatening complete atrioventricular block in Kearns-Sayre syndrome

Kearns-Sayre syndrome is a rare mitochondrial disorder with defined diagnostic criteria. Knowledge of these diagnostic criteria and early diagnosis are important to ensure periodic electrocardiograms for identification of cardiac conduction disorders, which are the most important prognostic factor of the disease. We report on a 9-year-old girl with rapid development of a life-threatening complete atrioventricular block within 10 months and discuss the importance and time interval of regular electrocardiograms. Our patient survived by placing a temporary transvenous pacemaker lead followed by permanent pacemaker implantation a few days later.

Kearns-Sayre syndrome presenting as complete heart block

Kearns-Sayre syndrome (KSS) is a rare mitochondrial disorder characterized by large-scale deletions of mitochondrial DNA. Neuromuscular and cardiac conduction systems are most commonly involved in these patients. Here, we discuss a 10-year-old patient with diabetes mellitus who presented in complete heart block leading to the diagnosis of KSS. The cardiovascular complications of this syndrome are reviewed and discussed.

Torsades de pointes in a patient with Kearns-Sayre syndrome: a fortunate finding

We present a case of a 33-year-old woman with Kearns-Sayre syndrome (KSS) who had a pacemaker implanted for complete heart block postpartum and was found to have torsades de pointes. KSS is a rare encephalomyopathy associated with varying levels of central nervous system involvement, typically resulting in progressive external opthalmoplegia and retinal degeneration. Onset of cardiac conduction disease can be insidious and is a strong predictor of sudden cardiac death. The mainstay of treatment has been the judicious implantation of pacemakers. However, as highlighted in this case, patients who have an underlying cardiomyopathy may be more appropriately treated with an implantable cardioverter defibrillator.

Chronic progressive ophthalmoplegia with large-scale mtDNA rearrangement: can we predict progression?

The prognosis of chronic progressive ophthalmoplegia with large-scale mitochondrial DNA (mtDNA) may strikingly vary from mild slowly progressive myopathy to severe multi-organ involvement. Evaluation of the disease course at the beginning of the disease is reputed impossible. To address the existence of predictive prognostic clues of these diseases, we classified 69 patients with chronic progressive ophthalmoplegia and large size mtDNA deletion into two groups according to the presence of manifestations from brain, inner ear or retina. These manifestations were present in 29 patients (CPEO/+N group) and absent in 40 patients (CPEO/-N group). We retrospectively established the clinical history of the patients and characterized their genetic alteration (amount of residual normal mtDNA molecules, site, size and percentage of the mtDNA deletion in 116 DNA samples from muscle, blood, urinary and buccal cells). In both clinical groups, the disease was progressive and heart conduction defects were frequent. We show that the CPEO/+N phenotype segregated with severe prognosis in term of rate of progression, multi-organs involvement and rate of survival. Age at onset appeared a predictive factor. The risk to develop a CPEO/+N phenotype was high when onset was before 9 years of age and low when onset was after 20 years of age. The presence and proportion of the mtDNA deletion in blood was also significantly associated with the CPEO/+N phenotype. This study is the first to establish the natural history of chronic ophthalmoplegia with mtDNA deletion in a large series of patients and to look for parameters potentially predictive of the patients' clinical course.

Chronic Progressive External Ophthalmoplegia

INTRODUCTION

Chronic progressive external ophthalmoplegia is a common mitochondrial disease that shares clinical, enzymatic, and genetic features with other mitochondrial disorders. Effective treatment does not exist, and corrective surgery of the ptosis as a palliative measure is a treatment option.

PATIENTS AND METHODS

This was a retrospective study of 10 years' duration gathering patients with the diagnosis. Information related to clinical features, ancillary tests, and genetic data was obtained from our patients.

RESULTS

Six patients were identified with this disease, 5 of them women, aged 44 to 72 years. All patients presented with ptosis, and in 50% of the patients it was asymmetric. Half of the patients noted mild dysphagia for liquids. The CPK and acetylcholine receptor antibody levels were normal. Jitter was increased in half of the patients and ragged-red fibers were present in 5 of them. The most common enzyme alteration was the combined deficit of complexes I and IV. Familial forms were not found among our patients. The most common genetic anomaly was a single deletion in the mitochondrial DNA.

CONCLUSION

Knowledge of this disorder enables us to avoid the use of drugs with significant side effects in cases of ptosis and ophthalmoplegia that do not respond to anticholinesterases.

Pediatric autonomic disorders

The scope of pediatric autonomic disorders is not well recognized. The goal of this review is to increase awareness of the expanding spectrum of pediatric autonomic disorders by providing an overview of the autonomic nervous system, including the roles of its various components and its pervasive influence, as well as its intimate relationship with sensory function. To illustrate further the breadth and complexities of autonomic dysfunction, some pediatric disorders are described, concentrating on those that present at birth or appear in early childhood.

Heart Transplantation for Progressive Cardiomyopathy as a Manifestation of MELAS Syndrome

Mitochondrial diseases represent a heterogeneous group of disorders associated with a wide array of clinical manifestations. The presentation of patients with mitochondrial pathology largely depends upon the dysfunction of organ systems with large metabolic/energy requirements, including cardiac, neurologic, and musculoskeletal. In particular, mitochondrial myocardial disease can be progressive resulting in congestive heart failure and end-stage heart disease. This article reviews the role of heart transplantation for a particular variant of mitochondrial disorder, mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome, and discusses perioperative management issues related to transplantation for mitochondrial cardiomyopathies.

Kearns-Sayre Syndrome: A Case Report and Review of Cardiovascular Complications

Kearns-Sayre syndrome (KSS) is a rare genetic abnormality. Classified as a mitochondrial cytopathy, the primary pathology of this syndrome is a disturbance of mitochondrial DNA, which codes for the proteins required for the respiratory chain reaction. Onset occurs before age 20, and is manifest as chronic progressive external ophthalmoplegia and retinal degeneration. Management issues of KSS include prophylactic cardiac pacing for conduction defects, which has been shown to improve survival. Other clinical considerations relate to dietary supplements to attempt to control the progressive effects of the disease.

White matter involvement in mitochondrial diseases

White matter involvement is recently being realized as a common finding in mitochondrial disorders. It is considered an inherent part of the classical mitochondrial syndromes which are usually associated with alterations in the mitochondrial DNA such as: Leigh disease, Kearns-Sayre syndrome, mitochondrial encephalomyopathy lactic acidosis, and stroke like episodes, mitochondrial neuro-gastro-intestinal encephalomyopathy and Leber's hereditary optic neuropathy. White matter involvement is also described in mitochondrial disorders due to mutations in the nuclear DNA which are transmitted in an autosomal pattern. MRI findings suggestive of a mitochondrial disease are: small cyst-like lesions in abnormal white matter, involvement of both cerebral and cerebellar white matter, and a combination of a leukoencephalopathy with bilateral basal ganglia lesions. The clinical manifestations may be disproportionate to the extent of white matter involvement. Other organs may frequently be involved. The onset is often in infancy with a neurodegenerative course. The finding of a leukoencephalopathy in a patient with a complex neurologic picture and multisystem involvement should prompt a thorough mitochondrial evaluation.

SANDO: another presentation of mitochondrial disease

PURPOSE

To describe a unique mitochondrial syndrome that may present with the combination of ocular manifestations, sensory symptoms, and speech dysfunction.

DESIGN

Case report.

METHODS

Case report and review of the literature.

RESULTS

A 43-year-old man presented with a Sensory Ataxic Neuropathy, Dysarthria, and Ophthalmoparesis (SANDO). Nerve conduction studies showed a sensory ganglionopathy. Skeletal muscle biopsy revealed ragged red fibers, and polymerase chain reaction analysis of the tissue demonstrated multiple mitochondrial DNA deletions.

CONCLUSION

Mitochondrial disease should be considered in cases of external ophthalmoplegia, especially if a sensory ganglionopathy and dysarthria are present.

Progressive external ophthalmoplegia characterized by multiple deletions of mitochondrial DNA: unraveling the pathogenesis of human mitochondrial DNA instability and the initiation of a genetic classification

Over the last decade, many sporadic and familial cases have been reported with multiple deletions of mitochondrial DNA (mtDNA) in postmitotic tissues. Most patients suffer from progressive external ophthalmoplegia (PEO) and may have a nuclear gene defect that predisposes to the accumulation of mtDNA deletions. Recently, positional cloning has led to the discovery of mutations in four such nuclear genes. Some mutations are dominant and others recessive. In all autosomal mutations, defective mtDNA replication and/or repair are probably responsible for the generation of secondary mtDNA deletions. There are also data suggestive of a prominent pathogenic role for disturbed nucleotide metabolism. We here present a tentative genotype-phenotype correlation. Since clinical presentations are heterogeneous and overlap with different previously described clinical syndromes, we advocate the use of a genetic, instead of a clinical, classification of disorders with multiple mtDNA deletions.

Myopathies

Electrodiagnostic studies are an important adjunct to the clinical examination of a patient with a suspected myopathy; however, the clinical examination is crucial in making an accurate diagnosis, because electrodiagnostic studies have only a limited role in delineating with certainty the underlying myopathic disorder. Hereditary and acquired myopathies are reviewed in this article, with particular emphasis on distinguishing clinical and electrodiagnostic features. The hereditary myopathies that are discussed include the muscular dystrophies and the congenital distal mitochondrial, and metabolic myopathies. Acquired myopathies, including inflammatory, endocrine, and toxic myopathies, as well as those associated with systemic illness, are briefly reviewed.

Recessive POLG mutations presenting with sensory and ataxic neuropathy in compound heterozygote patients with progressive external ophthalmoplegia

Autosomal recessive progressive external ophthalmoplegia is a mitochondrial disease characterized by accumulation of multiple large-scale deletions of mitochondrial DNA. We previously reported missense mutations in POLG, the gene encoding the mitochondrial DNA polymerase gamma in two nuclear families compatible with autosomal recessive progressive external ophthalmoplegia. Here, we report a novel POLG missense mutation (R627W) in a sporadic patient and we provide genetic support that all these POLG mutations are actually causal and recessive. The novel patient presented with sensory ataxic neuropathy and has the clinical triad of sensory ataxic neuropathy, dysarthria and ophthalmoparesis (SANDO). This is the first finding of a genetic cause of Sensory Ataxic Neuropathy, Dysarthria and Ophthalmoparesis and it implies that this disorder may actually be a variant of autosomal recessive progressive external ophthalmoplegia. Sensory neuropathy is the initial feature in Belgian compound heterozygote autosomal recessive progressive external ophthalmoplegia patients, all carrying the POLG A467T mutation, which occurs at a frequency of 0.6% in the Belgian population.

Neonatal presentation of ventricular tachycardia and a Reye-like syndrome episode associated with disturbed mitochondrial energy metabolism

BACKGROUND

Hyperammonemia, hypoglycemia, hepatopathy, and ventricular tachycardia are common presenting features of carnitine-acylcarnitine translocase deficiency (Mendelian Inheritance in Man database: *212138), a mitochondrial fatty acid oxidation disorder with a lethal prognosis. These features have not been identified as the presenting features of mitochondrial cytopathy in the neonatal period.

CASE PRESENTATION

We describe an atypical presentation of mitochondrial cytopathy in a 2 day-old neonate. She presented with a Reye-like syndrome episode, premature ventricular contractions and ventricular tachycardia. Initial laboratory evaluation exhibited a large amount of 3-methylglutaconic acid on urine organic acid analysis, mild orotic aciduria and a nonspecific abnormal acylcarnitine profile. The evaluation for carnitine-acylcarnitine translocase deficiency and other fatty acid oxidation disorders was negative. The patient later developed a hypertrophic cardiomyopathy and continued to be affected by recurrent Reye-like syndrome episodes triggered by infections. A muscle biopsy exhibited signs of a mitochondrial cytopathy. During the course of her disease, her Reye-like syndrome episodes have subsided; however, cardiomyopathy has persisted along with fatigue and exercise intolerance.

CONCLUSIONS

This case illustrates that, in the neonatal period, hyperammonemia and ventricular tachycardia may be the presenting features of a lethal carnitine-acylcarnitine translocase deficiency or of a mitochondrial cytopathy, associated with a milder clinical course. This association broadens the spectrum of presenting phenotypes observed in patients with disturbed mitochondrial energy metabolism. Also, the presence of 3-methylglutaconic aciduria suggests mitochondrial dysfunction and mild orotic aciduria could potentially be used as a marker of mitochondrial disease.