Cases reported "Muscular Diseases"

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1/9. Beta-enolase deficiency, a new metabolic myopathy of distal glycolysis.

    A severe muscle enolase deficiency, with 5% of residual activity, was detected in a 47-year-old man affected with exercise intolerance and myalgias. No rise of serum lactate was observed with the ischemic forearm exercise. Ultrastructural analysis showed focal sarcoplasmic accumulation of glycogen beta particles. The enzyme enolase catalyzes the interconversion of 2-phosphoglycerate and phosphoenolpyruvate. In adult human muscle, over 90% of enolase activity is accounted for by the beta-enolase subunit, the protein product of the ENO3 gene. The beta-enolase protein was dramatically reduced in the muscle of our patient, by both immunohistochemistry and immunoblotting, while alpha-enolase was normally represented. The ENO3 gene of our patient carries two heterozygous missense mutations affecting highly conserved amino acid residues; a G467A transition changing a glycine residue at position 156 to aspartate, in close proximity to the catalytic site, and a G1121A transition changing a glycine to glutamate at position 374. These mutations were probably inherited as autosomal recessive traits since the mother was heterozygous for the G467A and a sister was heterozygous for the G1121A transition. Our data suggest that ENO3 mutations result in decreased stability of mutant beta-enolase. Muscle beta-enolase deficiency should be considered in the differential diagnosis of metabolic myopathies due to inherited defects of distal glycolysis.
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keywords = glycolysis
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2/9. 31P NMR spectroscopy and ergometer exercise test as evidence for muscle oxidative performance improvement with coenzyme Q in mitochondrial myopathies.

    Two patients with mitochondrial encephalomyopathy due to complexes I and IV deficiencies received 150 mg/d of coenzyme Q10 (CoQ). We studied them with a bicycle ergometer exercise test and 31P NMR spectroscopy before and after 10 months of treatment. Before treatment, we observed a low phosphocreatine/inorganic phosphate (PCr/P(i)) resting value along with abnormally high resting lactate concentration. During exercise, there was a pronounced acidosis with delayed kinetics of postexercise recovery for blood lactate, pH, PCr, and PCr/P(i) ratio. Oxygen uptake during exercise was reduced while the lowering of the ventilatory threshold indicated an early activation of glycolysis. After treatment, the bicycle ergometer exercise test indicated a significant improvement with a decrease in resting blood lactate level, an increase in oxygen consumption during exercise, and an increase in the kinetics of lactate disappearance during the recovery period. A shift of the ventilatory threshold to higher workload was present. 31P NMR spectroscopy confirmed the improvement, showing a significant increase in the PCr/P(i) ratio at rest and in the kinetics of recovery for pH, PCr, and PCr/P(i) ratio following exercise in patient 1. For patient 2, we observed a less pronounced acidosis correlated with a lesser amount of Pi produced during exercise. These observations indicate an improvement of mitochondrial function and a shift from high to low glycolytic activity in both patients consequent to CoQ treatment.
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keywords = glycolysis
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3/9. phosphorus magnetic resonance spectroscopy of partially blocked muscle glycolysis. An in vivo study of phosphoglycerate mutase deficiency.

    In vivo phosphorus magnetic resonance spectroscopy was used to evaluate the changes in muscle bioenergetics in a patient with a partial glycolytic block. phosphoglycerate mutase-deficient muscle showed the following evidence: Abnormal accumulation of sugar phosphates does occur, even when 6% enzyme activity is present. The elimination of sugar phosphates was faster than in complete glycolytic blocks. Mild intracellular acidosis occurred during ischemic exercise. The energy state was slightly low at rest but not during exercise. Postexercise recovery was mildly slowed. These findings suggest that phosphorus magnetic resonance spectroscopy can detect partial defects, as well as full glycolytic blocks, in muscle metabolism.
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keywords = glycolysis
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4/9. An unusual metabolic myopathy: a malate-aspartate shuttle defect.

    Studies on a 27-year-old man with a 3-year history of exercise-induced muscle pain, passage of red urine and elevated serum creatine kinase are described. Histological examination of a biopsy from quadriceps revealed non-specific myopathic changes with occasional clusters of subsarcolemmal mitochondria. The phosphorylase stain was normal. Phosphorous nuclear magnetic resonance (NMR) spectroscopy studies of gastrocnemius and flexor digitorum superficialis muscles showed no abnormalities at rest. During aerobic exercise there was an abnormally rapid decrease in phosphocreatine concentration but the pH remained within the normal range. There was a build-up of phosphomonoester (probably glucose 6-phosphate), usually indicative of a block in glycolysis. However, a primary defect in the glycolytic pathway seemed unlikely because muscle acidified normally during ischaemic exercise. Recovery from exercise was unusual in that phosphocreatine resynthesis and inorganic phosphate disappearance followed similar prolonged time courses (in control subjects the rate of inorganic phosphate disappearance was about twice as fast as the rate of phosphocreatine resynthesis). The transport of inorganic phosphate into the mitochondria appeared to be delayed. These slow recovery data suggested that oxidative metabolism was impaired. However, with all substrates tested, isolated muscle mitochondria had rates of oxygen uptake that were similar to control values, thereby ruling out a primary defect in mitochondrial respiration. A system involving several mitochondrial transport systems, the malate-aspartate shuttle, was measured. The activity in the patient's isolated mitochondria was less than 20% of the activity present in samples from control subjects. This patient is the only one so far reported with a defect involving the malate-aspartate shuttle system.
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keywords = glycolysis
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5/9. Osteomalacic myopathy.

    muscles from two cases of osteomalacia were studied histochemically and electron-microscopically. Histopathological finding were common in these two cases. There are (1) myopathic changes such as scattered muscle fiber atrophy, necrosis, and internal uuclei, (2) derangement of intermyofibrillar network. and (3) type II fiber atrophy. Electron-microscopical finding corresponded well with light microscopical findings. These are distinct pathological features and deserves to be called osteomalacic myopathy. As the pathogenetic mechanism of this myopathy, phosphate depletion in the muscle cells resulting in disturbed glycolysis, and decreased vitamin d effects on muscle cells resulting in diminished calcium uptake by sarcoplasmic reticulum, are considered to be the most important two factors.
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keywords = glycolysis
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6/9. Human muscle phosphoglycerate mutase deficiency: newly discovered metabolic myopathy.

    Muscle phosphoglycerate mutase activity was decreased (5.7 percent of the lowest control value) in a 52-year-old man with intolerance for strenuous exercise and recurrent pigmenturia since adolescence. All of the other enzymes of glycolysis had normal activities, and glycogen concentration was normal. Electrophoretic, heat lability, and mercury inhibition studies showed that the small residual activity in the patient's muscle was represented by the brain (BB) isoenzyme of phosphoglycerate mutase, suggesting a genetic defect of the M subunit which predominates in normal muscle. The prevalence of the BB isoenzyme in other tissues, including muscle culture, may explain why symptoms were confined to muscle.
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ranking = 0.2
keywords = glycolysis
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7/9. Clinical varieties of neuromuscular disease in debrancher deficiency.

    Two men and one woman with debrancher deficiency had symptoms and signs of neuromuscular disease. The two men had adult-onset and slowly progressive weakness, distal muscle wasting, "mixed" electromyographic patterns, and slow nerve conduction velocities; the initial diagnosis was charcot-marie-tooth disease in one patient and motor neuron disease in the other. The woman had stunted growth, delayed motor milestones, and lifelong nonprogressive weakness. A muscle biopsy specimen showed severe vacuolar myopathy in all three cases. The glycogen concentration was increased threefold to sixfold and had an abnormal iodine spectrum. Anaerobic glycolysis in vitro showed impaired use of endogenous and exogenous glycogen but normal use of hexose-phosphate glycolytic intermediates. These three cases illustrated the clinical variety of neuromuscular disease in debrancher deficiency. In patients with weakness of adult onset, the diagnosis is impossible to make without performing a muscle biopsy.
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ranking = 0.2
keywords = glycolysis
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8/9. emetine myopathy: two case reports with pathobiochemical analysis.

    We report two female patients with a history of alcohol abuse presenting with proximal painful muscle weakness following aversion therapy with emetine hydrochloride. Muscle biopsy of Case 1 showed a reversible floccular-shaped loss of myosin ATPase and dehydrogenase, an accumulation of PAS positive material, and a normal lipid content. Repeat biopsy showed core change with no focal loss of myosin ATPase. In Case 2, muscle biopsy was taken 1 month after commencement of emetine therapy and revealed similar but milder changes to Case 1. Electron microscopy revealed Z-band streaming with a decrease or loss of mitochondria. Sarcotubular systems appeared normal in shape and size. Anaerobic glycolysis on homogenate from the initial biopsy of Case 1 showed generalized reduction of lactate formation, which returned to normal in the repeat biopsy.
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ranking = 0.2
keywords = glycolysis
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9/9. A new variant case of muscle phosphofructokinase deficiency, coexisting with gastric ulcer, gouty arthritis, and increased hemolysis.

    Muscle phosphofructokinase (PFK) deficiency includes both clinically and genetically heterogeneous conditions. A 22-year-old man with muscle PFK deficiency due to previously unrecognized mutation was admitted because of gastric ulcer. He had noticed mild fatigability on vigorous exercise, but had never experienced painful cramps and myoglobinuria. His history included five time relapses of gastric ulcer and gouty arthritis at ages 19 and 21 years. His laboratory data showing impaired muscle glycolysis, increased hemolysis, and myogenic hyperuricemia had aspects in common with those reported for the classic form of this disease, except that lactate concentrations in his blood increased considerably after exercise. The mutant PFK enzyme of this patient, who was demonstrated to have a missense mutation, could exert some catalytic activity that permitted glycolytic flux in vivo, thus leading to the absence of typical myopathic symptoms. The association of relapsing gastric ulcer with muscle PFK deficiency was detected for the first time. There is a possibility that oxygen radical-induced tissue damage resulting from increased hypoxanthine on exertion plays a role in the pathogenesis of ulceration, since the patient is more tolerant to exercise than reported cases with the classic form of muscle PFK deficiency.
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keywords = glycolysis
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