Broadening the phenotypic spectrum of Pearson syndrome: Five new cases and a review of the literature.

Pearson syndrome (PS) is a multisystem mitochondrial respiratory chain disorder typically characterized by sideroblastic anemia and exocrine pancreatic insufficiency. PS is caused by a single large-scale mitochondrial DNA (mtDNA) deletion. PS classically presents in the first year of life and may be fatal in infancy. Children who survive PS may progress to develop Kearns-Sayre syndrome later in life. The full phenotypic spectrum and prognosis of the condition continue to evolve. Here we report five new patients with PS with unique clinical presentations, including four patients with onset later than previously reported in the literature, and one patient with prenatal onset of symptoms. The timing and unique features of these presentations support an expanded phenotypic spectrum of single large-scale mtDNA deletion syndromes (SLSMDS) and reinforce the importance of including SLSMDS in the differential for children with complex multisystem presentations.

Mitochondrial Disorder: Kearns-Sayre Syndrome.

Mitochondrial diseases are multisystem disorders: anemia, myopathy, lactic acidosis, CNS abnormality, endocrine abnormalities, renal disease, sensorineural deafness, and retinal involvement. The clinical abnormalities are heterogeneous, and they usually begin in childhood. Premature death occurs because of cardiac conduction defects. The onset is usually before 20 years of age. The fundus shows pigmentary retinopathy, with a salt-and-pepper appearance (Fig. 30.1), but vision remains good in most patients. Systemic involvement includes chronic progressive external ophthalmoplegia (CPEO), with ptosis being the most common complaint, and cardiomyopathy. Other variable features are short stature; cerebellar symptoms; weakness of muscles of the face, pharynx, trunk, or extremities; and progressive hearing loss. Full-field ERG does show evidence of generalized retinal dysfunction, involving both rods and cones. Skeletal muscle biopsy shows ragged red fibers and abnormal mitochondria.

NEW OBSERVATIONS REGARDING THE RETINOPATHY OF GENETICALLY CONFIRMED KEARNS-SAYRE SYNDROME.

PURPOSE: To report novel retinal findings in Kearns-Sayre syndrome and correlate degree of retinopathy with other clinical findings. METHODS: Observational case series of patients from Saudi Arabia with retinal and neuroophthalmologic examinations, medical chart review, and mitochondrial genetic evaluation. RESULTS: The three unrelated patients had progressive external ophthalmoplegia and pigmentary retinopathy bilaterally. Muscle biopsy in two of the cases revealed mitochondrial myopathy. All three had abnormal findings on neuroimaging and modestly reduced visual acuity in both eyes with a variable pigmentary retinopathy. One of the patients had bilateral subretinal fibrosis with a full-thickness macular hole in the right eye. All three patients had single, large-scale mitochondrial DNA (mtDNA) deletions (5.0-7.6 kb in size) with blood mtDNA heteroplasmy levels ranging from below 20% to 57%. Severity of pigmentary retinopathy did not correlate with severity of progressive external ophthalmoplegia, but did correspond grossly with electroretinographic abnormalities, just as the degree of ocular motility restriction and ptosis in each patient correlated with the size of their extraocular muscles on neuroimaging. In addition, the size of the single, large-scale mtDNA deletion and level of mtDNA heteroplasmy corresponded with degree of ocular motility restriction but not with severity of retinopathy. CONCLUSION: Subretinal fibrosis and macular hole are novel retinal observations which expand clinical profile in Kearns-Sayre syndrome. Genetic testing for mtDNA deletions and heteroplasmy in blood, muscle biopsy, careful ocular and retinal examination including electroretinography, and imaging are indispensable tests for this condition.

Renal Involvement in Neuropathy, Ataxia, Retinitis Pigmentosa (NARP) Syndrome: A Case Report.

We report a case of a patient who had the mitochondrial cytopathy complex of neuropathy, ataxia, and retinitis pigmentosa (NARP) syndrome diagnosed at age 11 years with a biopsy-proven kidney involvement that progressed to end-stage renal disease at age 21 years. Mutations of mitochondrial DNA (mtDNA) are maternally inherited and lead to mitochondrial cytopathies with predominant neurologic manifestations: psychomotor retardation, epilepsy, ataxia, neuropathy, and myopathy. Given the ubiquitous nature of mitochondria, cellular dysfunction can also appear in tissues with high metabolic turnover; thus, there can be cardiac, digestive, ophthalmologic, and kidney complications. Mutations in the MT-ATP6 gene of mtDNA have been shown to cause NARP syndrome without renal involvement. We report a patient who had NARP syndrome diagnosed at age 11 years in whom glomerular proteinuria was present very early after diagnosis. Although neurologic manifestations were stable over time, he developed worsening proteinuria and kidney function. He started dialysis therapy at age 21 years. Kidney biopsy confirmed the mitochondrial cytopathy histologically, with abnormal mitochondria seen on electron microscopy. The MT-ATP6 gene mutation was detected in the kidney biopsy specimen.

Mitochondrial cytopathies and the kidney.

Mitochondrial cytopathies include a heterogeneous group of diseases that are characterized by impaired oxidative phosphorylation. Current evidence suggests that renal involvement is probably more frequent than originally suspected but remains subclinical in a significant number of patients or is underestimated due to the severity of other clinical manifestations. Until recently, these diseases were thought to develop primarily in pediatric patients but patients that become symptomatic only in adulthood are now well recognized. From a renal standpoint, many patients with severe systemic disease and several patients with oligo-symptomatic clinical pictures have tubular defects, ranging from isolated tubular wasting of electrolytes to complete forms of renal Fanconi syndrome. Aside from rare cases of tubulo-interstitial and cystic diseases, other patients present with glomerular diseases that correspond in the majority of cases to focal segmental glomerulosclerosis lesions. Two specific entities should be singled out, namely the 3243 A>G mutation in the gene encoding for the mitochondrial leucine tRNA because it represents the most frequent form of mitochondrial glomerulopathy, and defects in the biosynthesis of coenzyme Q10 because they represent one of the few treatable forms of mitochondrial cytopathies.

Kearns-Sayre syndrome with facial and white matter extensive involvement: a (mitochondrial and nuclear gene related?) neurocristopathy?

The Authors report on a patient with Kearns-Sayre syndrome, large mtDNA deletion (7/kb), facial abnormalities and severe central nervous system (CNS) white matter radiological features, commonly attributed to spongy alterations. The common origin from neural crest cell (NCC) of facial structures (cartilagineous, osseous, vascular and of the peripheral nervous system) and of peripheral glia and partially of the CNS white matter are underlined and the facial and glial abnormalities are attributed to the abnormal reproduction/migration of NCC. In this view, the CNS spongy alterations in KSS may be not only a dystrophic process (leukodystrophy) but also a dysplastic condition (leukodysplasia). The Authors hypothesize that the symptoms may be related to mtDNA mutations associated to NCC nuclear gene abnormality. SOX 10 gene may be a nuclear candidate gene, as reported in some case of Waardenburg IV syndrome.

Clinical and Brain Magnetic Resonance Imaging Features in a Cohort of Chinese Patients with Kearns-Sayre Syndrome.

BACKGROUND: Kearns-Sayre syndrome (KSS) is a mitochondrial DNA (mtDNA) deletion disorder characterized by a triad of onset before 20 years of age, ophthalmoplegia, and pigmentary retinopathy. The heart and central nervous system are commonly involved. We summarized clinical and brain magnetic resonance imaging (MRI) features of a cohort of Chinese KSS patients. METHODS: Nineteen patients confirmed by muscle biopsy and mtDNA analysis were enrolled. We examined clinical profiles, mainly focusing on changes in electrocardiogram (ECG) and brain MRI. The correlation between genotype and phenotype was statistically analyzed. RESULTS: The mean age of onset was 9.6 ± 4.3 years, with all developing the classic triad at the time of diagnosis. Heart conduction block was detected in 63.2%, with four initially presenting as bundle branch block and developing into complete atrioventricular block over 3-72 months. Brain MRI showed symmetric high-T2 signals in 100% of cerebral and cerebellar white matter, as well as brainstem, 46.7% of basal ganglia, and 53.3% of thalamus. There were two patterns of cerebral white matter involvements, one with selective subcortical U-fibers and the other with periventricular white matter. The size of mtDNA deletion did not significantly correlate with age of onset or percentage of ragged blue fibers on muscle pathology. CONCLUSIONS: The clinical features of KSS evolve dynamically, affecting the cardiac conduction system predominantly, highlighting the significance of ECG monitoring. Brain MRI showed changes involving both the white matter and deep gray nuclei. Clinical presentation or severity of muscle pathological changes is not related to the size of mtDNA deletions.

Mitochondrial dysfunction in inherited renal disease and acute kidney injury.

Mitochondria are increasingly recognized as key players in genetic and acquired renal diseases. Most mitochondrial cytopathies that cause renal symptoms are characterized by tubular defects, but glomerular, tubulointerstitial and cystic diseases have also been described. For example, defects in coenzyme Q10 (CoQ10) biosynthesis and the mitochondrial DNA 3243 A>G mutation are important causes of focal segmental glomerulosclerosis in children and in adults, respectively. Although they sometimes present with isolated renal findings, mitochondrial diseases are frequently associated with symptoms related to central nervous system and neuromuscular involvement. They can result from mutations in nuclear genes that are inherited according to classic Mendelian rules or from mutations in mitochondrial DNA, which are transmitted according to more complex rules of mitochondrial genetics. Diagnosis of mitochondrial disorders involves clinical characterization of patients in combination with biochemical and genetic analyses. In particular, prompt diagnosis of CoQ10 biosynthesis defects is imperative because of their potentially reversible nature. In acute kidney injury (AKI), mitochondrial dysfunction contributes to the physiopathology of tissue injury, whereas mitochondrial biogenesis has an important role in the recovery of renal function. Potential therapies that target mitochondrial dysfunction or promote mitochondrial regeneration are being developed to limit renal damage during AKI and promote repair of injured tissue.

A rare case report of simultaneous presentation of myopathy, Addison's disease, primary hypoparathyroidism, and Fanconi syndrome in a child diagnosed with Kearns-Sayre syndrome.

UNLABELLED: Kearns-Sayre syndrome (KSS) is a rare mitochondrial DNA deletion syndrome defined as the presence of ophthalmoplegia, pigmentary retinopathy, onset less than age 20 years, and one of the following: cardiac conduction defects, cerebellar syndrome, or cerebrospinal fluid protein above 100 mg/dl. KSS may affect many organ systems causing endocrinopathies, encephalomyopathy, sensorineural hearing loss, and renal tubulopathy. Clinical presentation at diagnosis is quite heterogeneous and, usually, few organs are affected with progression to generalized disease early in adulthood. We present the case of a boy with KSS presenting at the age of 5 years with myopathy, Addison's disease, primary hypoparathyroidism, and Fanconi syndrome. The proper replacement treatment along with the administration of mitochondrial metabolism-improving agents had a brief ameliorating effect, but gradual severe multisystemic deterioration was inevitable over the next 5 years. CONCLUSION: This report highlights the fact that in case of simultaneous presentation of polyendocrinopathies and renal disease early in childhood, KSS should be considered.

Renal involvement in mitochondrial cytopathies.

Mitochondrial cytopathies constitute a group of rare diseases that are characterized by their frequent multisystemic involvement, extreme variability of phenotype and complex genetics. In children, renal involvement is frequent and probably underestimated. The most frequent renal symptom is a tubular defect that, in most severe forms, corresponds to a complete De Toni-Debré-Fanconi syndrome. Incomplete proximal tubular defects and other tubular diseases have also been reported. In rare cases, patients present with chronic tubulo-interstitial nephritis or cystic renal diseases. Finally, a group of patients develop primarily a glomerular disease. These patients correspond to sporadic case reports or can be classified into two major defects, namely 3243 A>G tRNA(LEU) mutations and coenzyme Q10 biosynthesis defects. The latter group is particularly important because it represents the only treatable renal mitochondrial defect. In this Educational Review, the principal characteristics of these diseases and the main diagnostic approaches are summarized.

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.

[Mitochondrial DNA deletions in Kearns-Sayre syndrome]. / Deleciones del ADN mitocondrial asociadas al síndrome de Kearns-Sayre.

INTRODUCTION: Kearns-Sayre syndrome (KSS) is a mitochondrial disorder characterized by progressive external ophthalmoplegia, pigmentary retinopathy, onset before 20 years, and ragged-red fibers on muscle biopsy. KSS has been associated to mitochondrial DNA (mtDNA) mutations. We report neurological manifestations and mtDNA deletions in KSS. METHODS: Six KSS patients underwent neurological examination, biochemical analysis (muscle enzymes, lactate, cerebrospinal fluid analysis), electromicrography, muscle biopsy (Gomori stain, electronic microscopy), electrocardiogram, echocardiography, MRI/CT scan. MtDNA deletions were studied in blood and muscle samples using Southern blotting and long polymerase chain reaction. RESULTS: Four males and two females (mean age: 27.7 years; range: 17-42; mean age at onset: 8.2 years) were studied. Initial symptoms were ptosis and gaze restriction, fatigue, exercise intolerance and proximal limb weakness. Syncope and neurosensory hypoacusia were initial symptoms in two patients. All of them presented a unique deletion in the mitochondrial genome, in heteroplasmy, and their size was in the range of 4,420 and 9,437 basis pairs. Three of these deletions are reported for the first time in this article. Most of the deletions are flanked by small direct repeats elements. CONCLUSIONS: Proximal muscle weakness and fatigue appear frequently in KSS patients during follow up. The syndrome in these patients has been caused by mtDNA deletions.

[Mitochondrial respiratory chain diseases. Evaluation and variability in 52 patients]. / Enfermedades de la cadena respiratoria mitocondrial. Evaluación y variabilidad en 52 pacientes.

INTRODUCTION: Clinical, electrophysiological, genetic and biochemical deficiencies variability were evaluated in 52 patients diagnosed of mitochondrial respiratory chain diseases (MRCD). PATIENTS AND METHODS: 26 men and 26 women, aged 19 to 79 years, were tested by clinical examination, electrophysiological techniques, muscle biopsy and genetic and biochemical studies. RESULTS: The patients were classified into seven phenotypes: myopathy, chronic progressive external ophthalmoplegia, progressive ophthalmoplegia plus ataxia, Kearns-Sayre syndrome, mitochondrial encephalomyopathy with lactic acidosis and stroke episodes (MELAS), myoclonic encephalopathy with ragged-red fibers (MERRF), and encephalopathies. Each phenotype may begin by different ways. The electromiography showed myopathy in 39 cases and various types of neuropathy in 10. Ragged-red COX negative fibers or widespread electron microscopic abnormalities were found in 47 cases. Simple deletions, multiple deletions and three different point mutations were observed. Deficiency of complexes I, II, III and IV were found alone or in different associations. CONCLUSIONS: MRCD shows wide variations in clinical, genetic and biochemical studies. Some patients with nonspecific manifestations, mainly of central nervous system, need careful attention and to be on account of diagnostic suspicion.

Is there a final common pathway in mitochondrial encephalomyopathies? Considerations based on an autopsy case of Kearns-Sayre syndrome.

A case of Kearns-Sayre syndrome (KSS) diagnosed 18 years prior to death due to stroke and heart failure with postnatal onset was followed over 15 years and confirmed by postmortem examination. Within the brain, an old cystic infarction of the left hemisphere was found. Other features included white matter gliosis and cerebellar atrophy. Equal or similar features were observed in other conditions thought to be due to failure of mitochondrial metabolism, therefore, a common evolution of neuropathological changes must be discussed.

Mitochondrial cytopathies.

Mitochondrial cytopathies represent a heterogeneous group of multisystem disorders which preferentially affect the muscle and nervous systems. They are caused either by mutations in the maternally inherited mitochondrial genome, or by nuclear DNA-mutations. Today, approximately 200 different disease causing mutations of mitochondrial DNA (mtDNA) are known, and due to the increased knowledge about nuclear genetics during the last few years, more and more nuclear mutations are being described. Owing to the non-uniform distribution of mitochondria in tissues and the co-existence of mutated and wildtype mtDNA (heteroplasmy) in these organelles, these disorders may present with a huge variety of symptoms, even if the same mutation is involved. Diagnostic investigations should include the measurement of serum and CSF lactate, neuroradiological tests and a muscle biopsy to show the characteristic ragged-red fibres and cytochrome c oxidase deficient cells and also to provide material for genetic analysis. To date, the treatment of these diseases remains supportive and should focus on typical complications such as cardiac dysrhythmia and endocrinopathy.

[Pulmonary thromboembolism as a late complication of mitochondrial myopathy (Kearns-Sayer syndrome ]. / Zatorowosc plucna jako odlegle powiklanie miopatii mitochondrialnej (zespól Kearns-Sayer'a).

A case of pulmonary thromboembolism with transient pulmonary hypertension of a rare cause is presented. In 24-year-old woman myasthenia was recognised on the ground of ptosis and fixation of eyes muscles from the 14th year of age. The treatment with mestinon was ineffective. Before planned thymectomy serious disturbances of heart rhythm and conduction were confirmed. Stimulator was implanted and thymectomy was done. No improvement of neurological state was observed despite the treatment with mestinone and prednisone. When she was 30 years old disease of lung appeared with fever, cough and parenchymal and pleural lesions of right lung. Antibiotic therapy was ineffective. CT scan and US examination revealed large thrombus inside the right auricle connected with stimulator electrodes. Embolisation of right pulmonary arteria was confirmed also. Treatment with heparin was ineffective and thrombectomy was performed. Exact neurological examination stated that the patient had no typical symptoms of myasthenia and that symptoms related with eyes and heart could be result of mitochondrial myopathy. Diagnosis was confirmed by EMG examination and muscle biopsy.

Manometric study in Kearns-Sayre syndrome.

Although swallowing difficulties have been described in patients with Kearns-Sayre syndrome (KSS), the spectrum of manometric characteristics of dysphagia is not yet well known. Moreover, it is conceivable that a combination of various degrees of swallowing difficulties with different patterns in manometric studies exist, each playing a major role in the prognosis, natural history, and quality of life of KSS patients. An 18-year-old girl diagnosed at the age of 5 years with KSS (muscle biopsy) was admitted to our department with an upper respiratory tract infection and dysphagia. Clinical examination revealed growth retardation, external ophthalmoplegia, pigmentary retinopathy, impaired hearing, and ataxia. An electrocardiogram revealed cardiac conduction defects (long Q-T), and brain magnetic resonance imaging showed abnormalities in the cerebellar hemispheres. A manometric and motility study for dysphagia was conducted and the pharynx and upper esophageal sphincter (UES) resting pressures were similar to control group values, but the swallowing peak contraction pressure of the pharynx and the closing pressure of the UES were very low and could not promote effective peristaltic waves. Relaxation and coordination of the UES were not affected although pharyngeal and upper esophagus peristaltic waves proved to be very low and, consequently, were practically ineffective. The patient was started on treatment comprising a diet rich in potassium, magnesium, and calcium, and oral administration of vitamin D and co-enzyme Q10 100 mg daily; she was discharged 6 days later with apparent clinical improvement.

Mitochondrial DNA defects in Brazilian patients with chronic progressive external ophthalmoplegia.

We report herein on eleven Brazilian patients with mitochondrial DNA (mtDNA) deletions, found among thirteen patients with chronic progressive external ophthalmoplegia (CPEO) and ragged-red fibers (RRF). The molecular data was correlated with the morphological and clinical findings. The muscle biopsies were studied by histochemistry, immunohistochemistry and DNA analysis. Muscle mtDNA deletions were mapped and quantitated by Southern blot analysis, polymerase chain reaction and sequencing. Of the eleven patients, ten had CPEO without multisystemic involvement and one had Kearns-Sayre syndrome. Three patients had multiple deletions, two of them with no apparent family history. Eight patients showed heteroplasmic single deletions, ranging in length from 2309 to 7566 bp; three of them had the same 'common deletion' of 4977 bp. The proportion of deleted mtDNA ranged from 14 to 89%. Immunohistochemical studies revealed decreased reactivity with the mtDNA-encoded subunit II of cytochrome c oxidase (COX) in all patients, but preserved activity with the nuclear-encoded COX subunit IV in COX-deficient fibers. Two cases presented a few COX-negative fibers with reduced COX IV immunostaining. We found a high frequency of mtDNA deletions in Brazilian patients with CPEO. There was no correlation between clinical severity, morphological findings and the size or amount of the mutated mtDNA in muscle, suggesting that there are still unknown factors influencing the disease phenotype.

Early retinal involvement in mitochondrial myopathy with mitochondrial DNA deletion.

BACKGROUND: Mitochondrial DNA (mtDNA) deletions have been reported in types of mitochondrial myopathy, including Kearns-Sayre syndrome (KSS). We examined mtDNA, skeletal muscle findings, and retinal electrophysiologic function in a patient believed to have incomplete KSS with ptosis and characteristic (so called salt and pepper) retinopathy, but without limitation of ocular motility and without other involvement of the central or peripheral nervous system. METHODS: Muscle biopsy specimens were examined by Gomori trichrome stain and electron microscopy. DNA extracted from muscle was examined by Southern blot analysis. Deleted mtDNA was sequenced by direct sequencing with polymerase chain reaction (PCR). Electroretinograms (ERG) and electrooculograms (EOG) were performed for electrophysiologic examination of the retina. RESULTS: There were no ragged red fibers in skeletal muscle specimens, although abnormal aggregation of mitochondria was observed on electron microscopic examination. An mtDNA deletion was detected. It spanned 5266-bp between the tRNASer gene and the ND5 gene. Electroretinographic and electrooculographic findings were normal, although extensive involvement of retinal pigment epithelium was observed on ophthalmoscopic examination. CONCLUSION: Detecting mtDNA deletion is more critical in diagnosing an incomplete phenotype of mitochondrial myopathy than is morphologic examination. We found that ophthalmoscopic fundus abnormalities preceded abnormalities on ERG and EOG.