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Journal of Primary Care & Community... 2023Bilateral lower extremity weakness and swelling can have several causes. Although often underdiagnosed, mitochondrial myopathy is more prevalent in the general...
Bilateral lower extremity weakness and swelling can have several causes. Although often underdiagnosed, mitochondrial myopathy is more prevalent in the general population than more commonly suspected diseases, such as Guillain-Barre syndrome. The clinical manifestations of mitochondrial disease can be broadly classified into 3 categories: chronic progressive external ophthalmoplegia, skeletal muscle-central nervous system syndromes, or pure myopathy. Cardiac abnormalities occur in 30% to 32% of cases, mostly in the form of hypertrophic cardiomyopathy, dilated cardiomyopathy, or conduction abnormalities. We report a case of a 21-year-old student who developed bilateral lower limb weakness, pain, and swelling diagnosed with mitochondrial myopathy on muscle biopsy. Initial laboratory tests revealed elevated creatinine kinase, brain natriuretic peptide, troponin, myoglobin, and lactic acid and reduced serum bicarbonate. Cardiac workup revealed systolic heart failure with a reduced ejection fraction. Endomyocardial biopsy revealed punctate foci of lymphocytic myocarditis. However, cardiac magnetic resonance imaging did not reveal either myocarditis or an infiltrative cardiac disease. An extensive autoimmune and infection work-up was negative. A muscle biopsy from the patient's rectus femoris revealed scattered ragged-blue fibers (stained with NADH dehydrogenase), scattered ragged-red fibers on modified Gomori trichrome stain, and cytochrome-c oxidase negative fibers with increased perimysial and endomysial connective tissue, consistent with active and chronic primary mitochondrial myopathy. The patient was treated successfully with furosemide, metoprolol, and methylprednisolone. Adult-onset mitochondrial myopathy is a rare clinical disorder, and our experience stresses the importance of using an inter-disciplinary team approach to diagnose uncommon clinical disorders with widely variable multisystem involvement.
Topics: Adult; Male; Humans; Young Adult; Myocarditis; Mitochondrial Myopathies; Muscle, Skeletal; Ophthalmoplegia, Chronic Progressive External; Lower Extremity
PubMed: 37162197
DOI: 10.1177/21501319231172697 -
American Journal of Physiology.... Oct 2011Exertional dyspnea limits exercise in some mitochondrial myopathy (MM) patients, but the clinical features of this syndrome are poorly defined, and its underlying...
Exertional dyspnea limits exercise in some mitochondrial myopathy (MM) patients, but the clinical features of this syndrome are poorly defined, and its underlying mechanism is unknown. We evaluated ventilation and arterial blood gases during cycle exercise and recovery in five MM patients with exertional dyspnea and genetically defined mitochondrial defects, and in four control subjects (C). Patient ventilation was normal at rest. During exercise, MM patients had low Vo(2peak) (28 ± 9% of predicted) and exaggerated systemic O(2) delivery relative to O(2) utilization (i.e., a hyperkinetic circulation). High perceived breathing effort in patients was associated with exaggerated ventilation relative to metabolic rate with high VE/VO(2peak), (MM = 104 ± 18; C = 42 ± 8, P ≤ 0.001), and Ve/VCO(2peak)(,) (MM = 54 ± 9; C = 34 ± 7, P ≤ 0.01); a steeper slope of increase in ΔVE/ΔVCO(2) (MM = 50.0 ± 6.9; C = 32.2 ± 6.6, P ≤ 0.01); and elevated peak respiratory exchange ratio (RER), (MM = 1.95 ± 0.31, C = 1.25 ± 0.03, P ≤ 0.01). Arterial lactate was higher in MM patients, and evidence for ventilatory compensation to metabolic acidosis included lower Pa(CO(2)) and standard bicarbonate. However, during 5 min of recovery, despite a further fall in arterial pH and lactate elevation, ventilation in MM rapidly normalized. These data indicate that exertional dyspnea in MM is attributable to mitochondrial defects that severely impair muscle oxidative phosphorylation and result in a hyperkinetic circulation in exercise. Exaggerated exercise ventilation is indicated by markedly elevated VE/VO(2), VE/VCO(2), and RER. While lactic acidosis likely contributes to exercise hyperventilation, the fact that ventilation normalizes during recovery from exercise despite increasing metabolic acidosis strongly indicates that additional, exercise-specific mechanisms are responsible for this distinctive pattern of exercise ventilation.
Topics: Acidosis; Adult; Blood Gas Analysis; Carbon Dioxide; Case-Control Studies; Dyspnea; Female; Humans; Lactates; Male; Middle Aged; Mitochondria, Muscle; Mitochondrial Myopathies; Oxygen Consumption; Physical Exertion; Pulmonary Ventilation; Respiratory Function Tests
PubMed: 21813873
DOI: 10.1152/ajpregu.00001.2011 -
Nature Reviews. Nephrology May 2016Mitochondria are increasingly recognized as key players in genetic and acquired renal diseases. Most mitochondrial cytopathies that cause renal symptoms are... (Review)
Review
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.
Topics: Acute Kidney Injury; Alkyl and Aryl Transferases; Animals; DNA, Mitochondrial; Humans; Kearns-Sayre Syndrome; Kidney Diseases; Mitochondria; Mitochondrial Myopathies; Mutation; Oxidative Phosphorylation; Reactive Oxygen Species; Ubiquinone
PubMed: 26804019
DOI: 10.1038/nrneph.2015.214 -
Journal of Neurology Dec 2022To assess natural history and 12-month change of a series of scales and functional outcome measures in a cohort of 117 patients with primary mitochondrial myopathy (PMM).
OBJECTIVES
To assess natural history and 12-month change of a series of scales and functional outcome measures in a cohort of 117 patients with primary mitochondrial myopathy (PMM).
METHODS
Twelve months follow-up data of 117 patients with PMM were collected. We analysed the 6-min walk test (6MWT), timed up-and-go test (× 3) (3TUG), five-times sit-to-stand test (5XSST), timed water swallow test (TWST), and test of masticating and swallowing solids (TOMASS) as functional outcome measures; the Fatigue Severity Scale and West Haven-Yale Multidimensional pain inventory as patient-reported outcome measures. PMM patients were divided into three phenotypic categories: mitochondrial myopathy (MiMy) without extraocular muscles involvement, pure chronic progressive external ophthalmoplegia (PEO) and PEO&MiMy. As 6MWT is recognized to have significant test-retest variability, we calculated MCID (minimal clinically important difference) as one third of baseline 6 min walking distance (6MWD) standard deviation.
RESULTS
At 12-month follow-up, 3TUG, 5XSST and FSS were stable, while TWST and the perceived pain severity (WHYMPI) worsened. 6MWD significantly increased in the entire cohort, especially in the higher percentiles and in PEO patients, while was substantially stable in the lower percentile (< 408 m) and MiMy patients. This increase in 6MWD was considered not significant, as inferior to MCID (33.3 m). NMDAS total score showed a slight but significant decline at 12 months (0.9 point). The perceived pain severity significantly worsened. Patients with PEO performed better in functional measures than patients with PEO&MiMy or MiMy, and had lower values of NMDAS.
CONCLUSIONS
PMM patients showed a slow global decline valued by NMDAS at 12 months; 6MWT was a more reliable measurement below 408 m, substantially stable at 12 months. PEO patients had better motor performance and lower NMDAS than PEO&MiMy and MiMy also at 12 months of follow-up.
Topics: Humans; Follow-Up Studies; Walk Test; Mitochondrial Myopathies; Ophthalmoplegia, Chronic Progressive External; Time Factors; Walking
PubMed: 35980466
DOI: 10.1007/s00415-022-11324-3 -
Journal of the American College of... Oct 2022The heart is commonly involved in maternally inherited mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome caused by the...
BACKGROUND
The heart is commonly involved in maternally inherited mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome caused by the MT-TL1 m.3243A>G mutation of the mitochondrial DNA. Heart transplantation (HTx) is controversial and has rarely been performed with conflicting results.
OBJECTIVES
We analyzed factors preventing HTx in consecutive adult patients with MELAS cardiomyopathy diagnosed and followed during the last 23 years in our HTx referral center.
METHODS
The series consists of 14 unrelated adult probands who were referred for evaluation of cardiomyopathy from 1998 to 2021. None had a suspected diagnosis of MELAS before referral. All patients underwent clinical and genetic visit and counseling, mitochondrial DNA sequencing, cardiovascular investigation (including right heart catheterization and endomyocardial biopsy in 10), multidisciplinary assessment, and biochemical tests. Family screening identified 2 affected relatives.
RESULTS
The cardiac phenotype was characterized by hypertrophic, concentric, nonobstructive cardiomyopathy that often evolved into a dilated cardiomyopathy-like phenotype. Of the 14 probands, 7 were potential candidates for HTx, 2 for heart and kidney Tx, and 1 was on the active HTx list for 3 years. None of the 10 probands underwent HTx. One is currently being evaluated for HTx. All had diabetes, hearing loss, and myopathy, and 10 had chronic kidney disease and progressive encephalomyopathy. During follow-up, 10 died from heart failure associated with multiorgan failure within 5 years of the genetic diagnosis.
CONCLUSIONS
High risk of stroke-like episodes, chronic kidney disease, and wasting myopathy in MELAS patients prevents activation of plans for HTx. As a result, the management of their cardiomyopathy in this syndromic context remains an unmet clinical need.
Topics: Cardiomyopathies; DNA, Mitochondrial; Heart Transplantation; Humans; MELAS Syndrome; Muscular Diseases; Mutation; Renal Insufficiency, Chronic
PubMed: 36202533
DOI: 10.1016/j.jacc.2022.04.067 -
Biochimica Et Biophysica Acta Aug 1998This review considers primary mitochondrial diseases affecting the respiratory chain. As diseases due to mitochondrial DNA defects defy traditional anatomical... (Review)
Review
This review considers primary mitochondrial diseases affecting the respiratory chain. As diseases due to mitochondrial DNA defects defy traditional anatomical classifications, we have not limited our discussion to neuromuscular disorders, but have extended it to include mitochondrial encephalomyopathies. Primary mitochondrial diseases can be due to mutations in either the nuclear or the mitochondrial genome. Nuclear mutations can affect (i) genes encoding enzymatic or structural mitochondrial proteins; (ii) translocases; (iii) mitochondrial protein importation; and (iv) intergenomic signaling. We review briefly recent molecular data and outstanding questions regarding these mendelian disorders, with special emphasis on cytochrome c oxidase deficiency and coenzyme Q10 deficiency. Mitochondrial DNA mutations fall into three main categories: (i) sporadic rearrangements (deletions/duplications); (ii) maternally inherited rearrangements (duplications); and (iii) maternally inherited point mutations. We summarize the most common clinical presentations and discuss pathogenic mechanisms, which remain largely elusive. Uncertainties about pathogenesis extend to the process of cell death, although excitotoxicity in neurons and apoptosis in muscle seem to have important roles.
Topics: Animals; Coenzymes; Cytochrome-c Oxidase Deficiency; DNA, Mitochondrial; Electron Transport Complex IV; Gene Deletion; Humans; Mitochondrial Encephalomyopathies; Mitochondrial Myopathies; Multigene Family; Neuromuscular Diseases; Point Mutation; Ubiquinone
PubMed: 9714805
DOI: 10.1016/s0005-2728(98)00113-3 -
Anesthesiology Oct 2006Mitochondria produce metabolic energy, serve as biosensors for oxidative stress, and eventually become effector organelles for cell death through apoptosis. The extent... (Review)
Review
Mitochondria produce metabolic energy, serve as biosensors for oxidative stress, and eventually become effector organelles for cell death through apoptosis. The extent to which these manifold mitochondrial functions are altered by previously unrecognized actions of anesthetic agents seems to explain and link a wide variety of perioperative phenomena that are currently of interest to anesthesiologists from both a clinical and a scientific perspective. In addition, many surgical patients may be at increased perioperative risk because of inherited or acquired mitochondrial dysfunction leading to increased oxidative stress. This review summarizes the essential aspects of the bioenergetic process, presents current knowledge regarding the effects of anesthetics on mitochondrial function and the extent to which mitochondrial state determines anesthetic requirement and potential anesthetic toxicity, and considers some of the many implications that our knowledge of mitochondrial dysfunction poses for anesthetic management and perioperative medicine.
Topics: Aged; Anesthetics; Animals; Apoptosis; Cardiovascular Diseases; Energy Metabolism; Humans; Ischemic Preconditioning; Mitochondria; Mitochondrial Diseases; Mitochondrial Myopathies; Neurodegenerative Diseases; Oxidative Stress; Perioperative Care; Sepsis
PubMed: 17006082
DOI: 10.1097/00000542-200610000-00029 -
Sexually Transmitted Infections Jun 2001Nucleoside reverse transcriptase inhibitors (NRTIs) remain the cornerstone of highly active antiretroviral therapy (HAART) combination regimens. However, it has been... (Review)
Review
Nucleoside reverse transcriptase inhibitors (NRTIs) remain the cornerstone of highly active antiretroviral therapy (HAART) combination regimens. However, it has been known for some time that these agents have the potential to cause varied side effects, many of which are thought to be due to their effects on mitochondria. Mitochondria, the key energy generating organelles in the cell, are unique in having their own DNA, a double stranded circular genome of about 16 000 bases. There is a separate enzyme present inside the cell that replicates mitochondrial DNA, polymerase gamma. NRTIs can affect the function of this enzyme and this may lead to depletion of mitochondrial DNA or qualitative changes. The study of inherited mitochondrial diseases has led to further understanding of the consequences of mutations or depletion in mitochondrial DNA. Key among these is the realisation that there may be substantial heteroplasmy among mitochondria within a given cell, and among cells in a particular tissue. The unpredictable nature of mitochondrial segregation during cellular replication makes it difficult to predict the likelihood of dysfunction in a given tissue. In addition, there is a threshold effect for the expression of mitochondrial dysfunction, both at the mitochondrial and cellular level. Various clinical and in vitro studies have suggested that NRTIs are associated with mitochondrial dysfunction in different tissues, although the weight of evidence is limited in many cases. The heterogeneity in the tissues affected by the different drugs raises interesting questions, and possible explanations include differential distribution or activation of these agents. This article reviews the major recognised toxicities associated with NRTI therapy and evidence for mitochondrial dysfunction in these complications. Data were identified through searching of online databases including Medline and Current Contents for relevant articles, along with abstracts and posters from recent conferences in the HIV and mitochondrial fields.
Topics: Acidosis, Lactic; DNA, Mitochondrial; HIV Infections; Hematologic Diseases; Humans; Lipodystrophy; Mitochondria; Mitochondria, Heart; Mitochondrial Myopathies; Pancreatitis; Peripheral Nervous System Diseases; Reverse Transcriptase Inhibitors
PubMed: 11402222
DOI: 10.1136/sti.77.3.158 -
Mitochondrion Sep 2021Mitochondrial myopathy (MM) encompasses a clinical heterogenous group of patients that can be difficult to diagnose. The aim of this study was to investigate if changes...
INTRODUCTION/BACKGROUND
Mitochondrial myopathy (MM) encompasses a clinical heterogenous group of patients that can be difficult to diagnose. The aim of this study was to investigate if changes in plasma lactate concentration during a 6-minute submaximal handgrip test (6MHGT) and a 20-minute post-exercise recovery period can be used as a diagnostic test for MM.
METHODS
Twenty-nine patients with MM and nineteen healthy controls (HC) performed an intermittent handgrip exercise test at ½ Hz for 6 min at 50% of maximal voluntary contraction force. We calculated the area under the curve (AUC) of change in plasma lactate during exercise and recovery and compared AUC between groups (MM vs. HC, and between MM subgroups based on disease severity).
RESULTS
The change in plasma lactate during exercise and recovery was similar in MM and HC (p = 0.65 and p = 0.57) and similar between MM subgroups (p ≥ 0.24).
CONCLUSION
Plasma lactate measured during and after a submaximal 6MHGT cannot be used as a diagnostic variable for MM.
Topics: Adult; Aged; Area Under Curve; Case-Control Studies; Exercise; Female; Hand Strength; Humans; Lactates; Male; Middle Aged; Mitochondrial Myopathies; Young Adult
PubMed: 34273558
DOI: 10.1016/j.mito.2021.07.002 -
EMBO Molecular Medicine Mar 2020Mitochondrial disorders affect 1/5,000 and have no cure. Inducing mitochondrial biogenesis with bezafibrate improves mitochondrial function in animal models, but there... (Observational Study)
Observational Study
Mitochondrial disorders affect 1/5,000 and have no cure. Inducing mitochondrial biogenesis with bezafibrate improves mitochondrial function in animal models, but there are no comparable human studies. We performed an open-label observational experimental medicine study of six patients with mitochondrial myopathy caused by the m.3243A>G MTTL1 mutation. Our primary aim was to determine the effects of bezafibrate on mitochondrial metabolism, whilst providing preliminary evidence of safety and efficacy using biomarkers. The participants received 600-1,200 mg bezafibrate daily for 12 weeks. There were no clinically significant adverse events, and liver function was not affected. We detected a reduction in the number of complex IV-immunodeficient muscle fibres and improved cardiac function. However, this was accompanied by an increase in serum biomarkers of mitochondrial disease, including fibroblast growth factor 21 (FGF-21), growth and differentiation factor 15 (GDF-15), plus dysregulation of fatty acid and amino acid metabolism. Thus, although potentially beneficial in short term, inducing mitochondrial biogenesis with bezafibrate altered the metabolomic signature of mitochondrial disease, raising concerns about long-term sequelae.
Topics: Bezafibrate; Humans; Mitochondria; Mitochondrial Myopathies; Organelle Biogenesis
PubMed: 32107855
DOI: 10.15252/emmm.201911589