Kearns–Sayre Syndrome Minus: Two Cases of Identical Large-Scale Mitochondrial DNA Deletions with Presentations outside the Classical Triad

A curious triad of retinitis pigmentosa, external ophthalmoplegia, and complete heart block was presented by Sayre et al. in 1958. Since then, the disorder named Kearns–Sayre syndrome (KSS) has come to represent patients with mitochondrial DNA deletions presenting before adulthood, primarily with chronic progressive external ophthalmoplegia (CPEO) and pigmentary retinopathy. However, it is increasingly noted that the presentations can well be variable despite similar genetic deletions. Here, we present two cases with identical large-scale mitochondrial DNA deletions but very dissimilar outlook.

Spinal cord involvement in Kearns-Sayre syndrome: a neuroimaging study

Purpose

Spinal cord involvement in Kearns-Sayre (KSS) syndrome could be more frequent than commonly thought. Our aims were to evaluate the involvement of the spinal cord in patients with KSS by means of MRI and to investigate possible correlations of spinal and brain disease with patient disability.

Methods

Eleven patients with KSS disease and spinal cord MRI were retrospectively recruited. The severity of spinal disease was defined as follows: grade 0 (none), grade 1 (focal), and grade 2 (extensive). We calculated a radiologic score of brain involvement based on typical features. We performed a chi-square test to correlate spinal cord and brain MRI involvement to patient disability. For significant variables, a contingency coefficient, phi factor, and Cramer’s V were also computed.

Results

Spinal cord lesions were detected in 6/11 patients, showing four patterns: involvement of gray matter, gray matter and posterior columns, posterior columns, and anterior columns. The severity of spinal disease was grade 1 in two and grade 2 in four patients. All patients showed brain involvement (9-point average for patients with spinal involvement and 10 for the others). A significant correlation was found between disability score and spinal cord involvement (χ² = 7.64; p = 0.022) or brain score (χ² = 26.85; p = 0.043). Significance for brain score-disability correlation increased with the spinal cord as a cofactor (χ² = 24.51; p = 0.017, phi factor = 1.201, Cramer’s V = 0.849, contingency effect = 0.767; p = 0.017).

Conclusion

Spinal cord lesions are common in KSS. Patients with spinal disease show higher disability than patients without spinal cord lesions, supporting the inclusion of dedicated acquisitions to routine MRI of the brain in patients with KSS.

Genetics of Mitochondrial Disease

Mitochondria are intracellular organelles responsible for adenosine triphosphate production. The strict control of intracellular energy needs require proper mitochondrial functioning. The mitochondria are under dual controls of mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). Mitochondrial dysfunction can arise from changes in either mtDNA or nDNA genes regulating function. There are an estimated ∼1500 proteins in the mitoproteome, whereas the mtDNA genome has 37 proteins. There are, to date, ∼275 genes shown to give rise to disease. The unique physiology of mitochondrial functioning contributes to diverse gene expression. The onset and range of phenotypic expression of disease is diverse, with onset from neonatal to seventh decade of life. The range of dysfunction is heterogeneous, ranging from single organ to multisystem involvement. The complexity of disease expression has severely limited gene discovery. Combining phenotypes with improvements in gene sequencing strategies are improving the diagnosis process. This chapter focuses on the interplay of the unique physiology and gene discovery in the current knowledge of genetically derived mitochondrial disease.

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.

Kearns-Sayre syndrome associated with trifascicular block and QT prolongation

Patients suffering from Kearns-Sayre syndrome (KSS) often develop conduction defects that may lead to syncope or sudden cardiac death. The association of conduction abnormalities with prolonged QT interval in these patients is very rare. We describe a patient with KSS and diabetes mellitus who suffered a torsades de pointes-induced syncopal attack, in the presence of trifascicular block and QT prolongation (QTc: 574 ms). The patient was successfully treated with permanent pacing. This case highlights that torsades de pointes represents a potential mechanism of syncope or sudden cardiac death in patients with KSS.

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.

Cardiac involvement in mitochondrial diseases. A study on 17 patients with documented mitochondrial DNA defects

BACKGROUND

Mutations of mitochondrial DNA have been demonstrated as causes of human mitochondrial diseases. While these disorders typically involve multiple organs, the effect of mitochondrial mutations on the heart has not been systematically studied.

METHODS AND RESULTS

We studied mitochondrial mutations and cardiac changes in 17 patients with Kearns-Sayre syndrome; ocular myopathy; myoclonus epilepsy with ragged red fibers (MERRF); and mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS). Cardiac involvement was evaluated by chest radiograph, ECG, His-bundle electrogram, and echocardiogram. All 3 patients with Kearns-Sayre syndrome had large deletions of mitochondrial DNA and disturbances in cardiac conduction. ECG abnormalities were found in 2 of 6 patients with ocular myopathy who showed large deletions of mitochondrial DNA. All 3 patients with MERRF had an A-to-G mutation at nucleotide position 8344; 2 had cardiomegaly, asymmetrical septal hypertrophy, and diffuse hypokinesis of the left ventricle. One patient with asymmetrical septal hypertrophy developed dilated cardiomyopathy 2 years later. All 5 patients with MELAS had an A-to-G mutation at nucleotide position 3243, and 2 had symmetrical left ventricular hypertrophy with or without abnormal wall motion.

CONCLUSIONS

The clinical features of cardiac involvement in mitochondrial diseases vary in the different subgroups of these disorders. Particular mitochondrial mutations can cause characteristic cardiac abnormalities.

Sinus dysrhythmia in Kearns-Sayre syndrome

Kearns-Sayre syndrome is the triad of progressive external ophthalmoplegia, pigmentary retinopathy, and complete AV block. The etiology is unknown, but is thought to be due to a mitochondrial DNA deletion. Reported electrocardiographic abnormalities include first-degree AV block, fascicular blocks, and complete heart block, as well as non-specific S-T segment changes and T wave abnormalities, but has not included sinus node dysfunction. We report a case with episodes of sinus arrest in an asymptomatic patient with Kearns-Sayre syndrome resulting in pauses lasting up to 6 seconds.

Erythrocyte and platelet fatty acids in retinitis pigmentosa

The fatty acid composition and the glutathione-peroxidase activity (GSH-Px) of erythrocytes and platelets, the production of malondialdehyde (MDA) by platelets and the activity of the main systems of transmembrane cation transport in erythrocyte have been studied in 12 patients (5 males and 7 females) affected by retinitis pigmentosa (RP). A remarkable increase of saturated fatty acids (SFA), particularly of stearic acid (C18:0), has been noted in these patients. The reduced unsaturated/saturated fatty acids ratio (PUFA/SFA) observed in both erythrocytes and platelets and the decrease of arachidonic acid in platelets may depend by an active peroxidation process as documented by the increase of MDA. Platelet glutathione-peroxidase (PTL-GSH-PX) and plasma retinol were in the normal range, whereas erythrocyte glutathione-peroxidase (E-GSH-PX), MDA and plasma alfa-toco-pherol were increased in patients with RP. The activities of Na(+)-K+ pump, cotransport and Na(+)-Li+ countertransport were normal in RP erythrocytes.

Neuropathology in Kearns-Sayre syndrome

The neuropathological changes found at autopsy in a case of Kearns-Sayre syndrome are described. We have previously analyzed the respiratory chain function in isolated muscle mitochondria and also described a large deletion of muscle mitochondrial DNA (mtDNA) in this case. The neuropathological examination revealed prominent neuronal degeneration and gliosis of the basal ganglia and there were bilateral areas of softening and total loss of nerve cells in the lenticular nuclei. The pallidum and caudate nucleus disclosed accumulation of iron-containing pigment. The white matter in the cerebrum, brain stem and cerebellum showed widespread and focally accentuated spongy change due to splitting of myelin lamellae. It is suggested that deficiency of respiratory chain enzymes due to the mtDNA deletion is of pathogenetic importance in the development of the described changes.

Ultrastructural findings in endomyocardial biopsy of patients with Kearns-Sayre syndrome

Kearns-Sayre syndrome is clinically defined by progressive external ophthalmoplegia, atypical retinitis pigmentosa and the potential occurrence of complete atrioventricular (AV) block. Right septal endomyocardial biopsy specimens from nine patients (four men and five women with a mean [+/- SD] [corrected] age of 36.3 +/- 14.4 years) with chronic progressive external ophthalmoplegia and mitochondrial skeletal myopathy were studied. Three patients had atypical retinal pigmentation. An atrioventricular or intraventricular conduction defect was observed in five patients. A pacemaker was prophylactically implanted in one patient because of abnormal conduction distal to the His bundle. Ultrastructural investigations revealed mitochondriosis in many heart muscle cells and an increased variability of mitochondrial form and size in all patients. In seven patients, 0.4 to 2.1% of all examined myocytes contained exclusively abnormal mitochondria. Three main types were observed: huge, mainly round mitochondria with concentric cristae; large, round or oval mitochondria with transverse or curved cristae; and small, vacuolated mitochondria. The volume density of myofibrils was reduced (41.9 +/- 11.1 compared with the normal value of 56.5 +/- 2.5 volume density [in percent], p less than 0.01) in these myocytes. Increasing numbers of vacuolated mitochondria correlated significantly with a reduction of myofibrils (r = -0.64, p less than 0.01). The data suggest that the ventricular myocardium of most patients with complete and even incomplete Kearns-Sayre syndrome is affected by disseminated mitochondrial cytopathy.

Progressive cytochrome c oxidase deficiency in a case of Kearns-Sayre syndrome: morphological, immunological, and biochemical studies in muscle biopsies and autopsy tissues

We report biochemical, immunological, and morphological findings in a patient with fatal Kearns-Sayre syndrome. Histochemical and biochemical findings from muscle biopsy specimens obtained 7 years apart documented the disease's evolution from a mild mitochondrial disorder affecting a small proportion of muscle fibers to a severe disorder affecting a large proportion of muscle fibers. Cytochrome c oxidase activity in muscle declined profoundly as the disease progressed, although the level of enzyme protein was normal, as shown by immunochemical techniques. Other organs were severely affected by the disease. Examination of postmortem tissue showed spongiosis in the frontal cortex, diffuse loss of Purkinje cells in the cerebellum, liver steatosis, and heart fibrosis with mitochondrial abnormalities. Cytochrome c oxidase activity was only slightly reduced in these organs.

Congestive heart failure due to mitochondrial cardiomyopathy in Kearns-Sayre syndrome

Despite extensive analysis of the ultrastructural changes in skeletal muscle fibers in chronic progressive external ophthalmoplegia (CPEO), similar changes in the heart muscle fibers of patients with cardiac involvement in CPEO, called Kearns-Sayre syndrome, have not been described in detail. We report the clinical long-term course in a patient with Kearns-Sayre syndrome in whom mitochondrial cardiomyopathy was suspected in vivo and was confirmed at autopsy as the underlying cause of severe dilative cardiomyopathy. Enlarged, abnormally structured, excessively augmented mitochondria and loss of myofibrils could be shown both in skeletal and heart muscle cells.

Myocardial ultrastructure in Kearns-Sayre syndrome

Myocardial ultrastructural changes are described in a twenty-five-year-old female with typical Kearns-Sayre syndrome. The electrocardiogram revealed complete atrioventricular block with an occasional torsades de pointes type of ventricular tachycardia. His bundle recording demonstrated HV block with normal AH interval. An endomyocardial biopsy showed "ragged-red fibers" by the modified Gomori trichrome stain, and on electron microscopy there were increased numbers of morphologically abnormal mitochondria: ie, gian mitochondria, a whorled pattern of the cristae, and electron-dense substances, and paracrystalline inclusions in the mitochondria. The patient has been well since pacemaker implantation, but she may develop a clinically overt cardiomyopathy due to progression of myocardial involvement.

Fatal mitochondrial cardiomyopathy in Kearns-Sayre syndrome with deficiency of cytochrome-c-oxidase in cardiac and skeletal muscle. An enzymehistochemical--ultra-immunocytochemical--fine structural study in longterm frozen autopsy tissue

Morphological studies in a 26-year-old man with long-standing Kearns-Sayre syndrome, with cardiac arrhythmias and a fatal congestive cardiomyopathy, revealed a mitochondrial myopathy of both skeletal and myocardial muscle (Hübner et al. 1986). Histochemical investigation of cytochrome-c-oxidase showed multiple enzyme defects of both cardiac and skeletal muscle present in myocytes with normal and abnormal numbers of mitochondria demonstrated by ultracytochemistry. Immunohistochemical studies with antibodies against the holoenzyme and various subunits revealed that in the heart the enzyme defect affected both contractile and conductive fibres and was characterized by a severe reduction but not a complete loss of nuclear and mitochondrially coded immunoreactive enzyme protein. In skeletal muscle, however, where up to 30% of the fibres lacked enzyme activity, immunoreactivity was reduced only very occasionally. These results are most consistent with a defective enzyme assembly in the inner mitochondrial membrane and probably indicate heterogeneity of mitochondria, i.e. organ-specific pathological reaction patterns.

Ophthalmoplegia plus, an electro-oculographic study

To find out whether the central structures governing conjugate eye movements are affected in ophthalmoplegia plus (OP), we conducted an electro-oculographic study in 6 patients suffering from OP with varying degrees of extraocular involvement and with mitochondrial changes in the skeletal musculature. All the patients presented alterations of the smooth pursuit and saccadic movements, of optokinetic nystagmus as well as of the vestibular reflexes and of visuovestibular interaction, thus confirming impairment of the central oculomotor structures and particularly of those of the archicerebellum and brainstem. These data suggest a supranuclear component in the pathogenesis of ophthalmoplegia and are in accord with the findings of brainstem spongiosis in OP, which in turn seem to express a multisystem pathological state of the mitochondria.

Asymmetric septal hypertrophy in kearns-sayre syndrome

Kearns-Sayre syndrome was diagnosed in a 40-year-old female patient admitted for evaluation of symptomatic bradycardia. In addition to the classic triad--external ophthalmoplegia, pigmentary retinopathy, and heart block--she also had secondary amenorrhea, hearing loss, diabetes, and increased concentrations of blood lactate and pyruvate as manifestations of this multisystem disease. The echocardiographic examination disclosed asymmetric septal hypertrophy with a septal diastolic thickness of 17 mm and a septum to free wall ratio of 1.5. The left ventricular size and function were normal. Thus, asymmetric septal hypertrophy may represent subclinical heart muscle involvement in Kearns-Sayre syndrome.

Near-fatal Kearns-Sayre syndrome. A case report and review of clinical manifestations

The Kearns-Sayre syndrome is a relatively uncommon condition which occurs in childhood and is characterized by neurologic dysfunction and abnormalities in atrioventricular (AV) conduction. The high mortality rate is directly attributable to the cardiovascular manifestations of this syndrome. We report a case, with documentation of a "near-fatal" episode, and review the pertinent clinical features of the syndrome.

Metabolic tapetoretinal degenerations

There are a number of metabolic diseases which cause tapetoretinal degeneration, suggesting that pure pigmentary retinopathy may also be metabolic in nature. On the other hand tapetoretinal degenerations may have various modes of inheritance, so we may conclude that the metabolic disorder at the basis of these diseases is not unique and that tapetoretinal degenerations are heterogenic. In this article, some 450 published reports on tapetoretinal degenerations are reviewed. Based on these reports, the clinical and ocular manifestations, laboratory and histopathological findings, inheritance patterns, and treatments of various syndromes characterized by tapetoretinal degenerations are described. It is hoped that the gathering together of this information in one source will acid in the future understanding of metabolically based eye disease.

Kearns syndrome: a heterogeneous group of disorders with CPEO, or a nosological entity?

In connection with 4 new cases of Kearns syndrome (multisystem form of mitochondrial CPEO), the condition was found to be present in slight to oligosymptomatic form in all 4 families. The marker symptom in subclinical patients was nearly always ptosis (sometimes very slight) and occasionally diabetes. In the literature other endocrine disorders, retinal anomalies, deafness, growth disturbances, etc., have been noted as subclinical symptoms in former generations. Heredity appears to be autosomal dominant in these 4 families, with very variable expressivity. The possibility that one gene is responsible for the disease seems to be plausible, but the marked variation in expressivity suggests a modifying influence of other alleles; in this sense, therefore, one may speak of multifactor inheritance. Supporting facts could also be found in the literature, where there was autosomal dominant heredity of the disease-carrying gene, but for its complete expression 'amplifying' factors (alleles) were needed. The pleiotropia of the disease-carrying gene is explained by a mitochondrial disorder of various organs. On the basis of the heredity, therefore, Kearns syndrome is not a syndrome but a disease. The most serious, most progressive and most extensive (multisystem) variant of Kearns disease is the infantile form, known as the 'Kearns-Sayre syndrome. When the expressivity of the disease is less extensive it usually occurs later in life and is less progressive: the adult form of Kearns disease.

Demyelinating radiculopathy in the Kearns-Sayre syndrome: a clinicopathological study

In the few previously autopsied patients with the Kearns-Sayre form of progressive ophthalmoplegia, the most prominent abnormalities have been in muscle, with less conspicuous changes in the central nervous system, primarily in the brainstem. Similar findings were present in the case reported here, but in addition there was severe demyelination in the initial few millimeters of the cranial and spinal motor roots distal to the glial-Schwann cell junction. Milder demyelination was observed in the dorsal spinal and afferent cranial nerve roots, including the eighth nerve, but deafness was due to virtually total destruction of the organ of Corti. Our observations suggest that a radiculopathy may be a feature in some cases of Kearns-Sayre syndrome.