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1/11. Facial anomalies in patients with cytochrome-c-oxidase (COX) deficiency: a dysneurulation.

    The authors report 3 cases of cytochrome-c-oxidase deficiency (2 cases of kearns-sayre syndrome and 1 case of chronic progressive external ophthalmoplegia) with central nervous system alterations and facial anomalies. The facial anomalies are high forehead, wide nasal bridge, upturned nose, long and flat philtrum (alterations depending on frontal-nasal-premaxillary structures which derive from prosencephalic neural crests), hypoplastic maxilla and mandible, ophthalmoplegia (alterations of maxilla and III-VI cranial nerve nuclei, which derive on the mesencefalic neural crests), low set ears, short neck (alterations of the 3rd, 4th branchial arch derivatives, which arise from rhombencephalic neural crests). The authors conclude that cytochrome-c-oxidase deficiency in embryonic stage can injure, in kearns-sayre syndrome and chronic progressive external ophthalmoplegia, distal tissues of face and central nervous system depending on neural crests, and that the symptomatology of these diseases can be ascribed to dysneurulation.
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ranking = 1
keywords = chronic progressive
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2/11. Functional respiratory chain studies in subjects with chronic progressive external ophthalmoplegia and large heteroplasmic mitochondrial dna deletions.

    The functional consequences of large heteroplasmic mtDNA deletions were investigated in a group of 6 patients with chronic progressive external ophthalmoplegia (CPEO) syndromes. State III respiration rates corrected for age were low with site I and II substrates in all cases and cytochrome oxidase activity was depressed. The severity of impairment varied and is consistent with inclusion of a variable percentage of non-functioning mitochondria (with deleted mtDNA) in the pellet. Western blot studies with a holocomplex antibody battery revealed no abnormalities in subunit content of complexes III and IV. A deficiency of several complex I subunits in 3 cases suggests that abnormal nuclear-mitochondrial regulation of complex I assembly may follow large mtDNA deletions.
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ranking = 2.5
keywords = chronic progressive
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3/11. Partial cytochrome oxidase (aa3) deficiency in chronic progressive external ophthalmoplegia. Histochemical and biochemical studies.

    Biochemical and histochemical studies were carried out on 2 patients with chronic progressive external ophthalmoplegia (CPEO). Histological examination revealed prominent ragged-red fibres in the Gomori trichrome stain and cytochrome oxidase staining revealed partial depletion of cytochrome oxidase with negative staining in some fibres with prominent subsarcolemmal mitochondrial aggregations. Polarographic studies with isolated intact skeletal muscle mitochondria revealed low State III respiration rates with NAD- and FAD-linked substrates. Cytochrome aa3 levels were depressed in the one case where a cytochrome difference spectra was recorded. Cytochrome oxidase levels were greatly depressed in muscle homogenate, whereas monoamine oxidase levels were in the normal range, indicating a selective depletion of the former enzyme complex. It is possible that deficiency of cytochrome oxidase may arise as an epiphenomenon in degenerating mitochondria rather than a primary deficiency.
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ranking = 2.5
keywords = chronic progressive
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4/11. Endocrine involvement in mitochondrial encephalomyopathy with partial cytochrome c oxidase deficiency.

    A 19-year-old man born with thyroprivic hypothyroidism, due to congenital development defect, manifested hypogonadism, stunted growth, chronic progressive external ophthalmoplegia (CPEO), diffuse muscle weakness and wasting, right bundle branch block, cerebral atrophy. Muscle biopsy showed mitochondrial abnormalities. Biochemical investigations on muscle disclosed partial (50%) cytochrome c oxidase deficiency, 58% decrease of cytochrome aa3 and 41% decrease of cytochrome b. enzyme-linked immunosorbent assay showed decrease of the immunologically active enzyme protein.
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ranking = 0.5
keywords = chronic progressive
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5/11. Partial deficiency of complexes I and IV of the mitochondrial respiratory chain in skeletal muscle of two patients with mitochondrial myopathy.

    Respiratory chain enzymes were studied in isolated mitochondria of two patients with mitochondrial myopathy. Both patients had been suffering from chronic progressive external ophthalmoplegia and abnormal muscular fatigability since late childhood. One of the patients exhibited the complete triad of symptoms characteristic of kearns-sayre syndrome. Venous lactate levels at rest and during minimal exercise were increased in both patients. Histochemical examination of muscle revealed ragged red fibres and intermingled fibres negative for cytochrome c oxidase. Biochemical studies showed decreased activities of complex I and complex IV of the respiratory chain in both patients. Reduced minus oxidized spectra of mitochondrial cytochromes revealed a decreased content of cytochrome aa3 in only one patient, but a normal content in the other. A combined deficiency of complexes I and IV in muscle might either be due to a deficiency of a single subunit common to both complexes or to a coincidental deficiency of both complexes expressed either in the same or in different fibres.
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ranking = 0.5
keywords = chronic progressive
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6/11. A mitochondrial encephalomyopathy with a partial cytochrome c oxidase deficiency of muscle.

    A 16 year old girl showed delayed psychomotor development. In infancy, exercise intolerance, cerebellar signs, deteriorated with increasing intercurrent infections, and disturbances of breathing and cardiac rhythm became manifest. From the age of 7 years there was chronic progressive psychomotor deterioration, with hypotonia, a bilateral pyramidal and cerebellar syndrome, and mild epilepsy. CSF pyruvate and lactate levels were elevated, and lactate content was elevated in the urine. There was an abnormally high rise of lactate levels on moderate exercise and an abnormal response to pyruvate loading. quadriceps muscle biopsies obtained at age 10 and 16 years showed ragged-red fibres, and a decreased cytochrome c oxidase activity and cytochrome aa3 content. Cytochrome c oxidase activity in fibroblasts was normal. Clinical signs and symptoms in association with a disturbance of mitochondrial energy metabolism led us to diagnosis of probable Leigh syndrome.
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ranking = 0.5
keywords = chronic progressive
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7/11. Skeletal muscle pathology in chronic progressive external ophthalmoplegia with ragged-red fibers.

    Histochemical investigations were carried out on skeletal muscle biopsies from ten patients with chronic progressive external ophthalmoplegia with ragged-red fibers (RRF). In addition to the RRF, mild myopathic change consisting of variation in size of both type 1 and 2 fibers was seen in all patients, as well as neuropathic change in eight. Scattered fibers with absent cytochrome c oxidase (CCO) activity (focal deficiency) were seen in all patients. In serial sections, CCO deficiency did not always occupy the entire length of a fiber but was localized segmentally to regions measuring several hundred micrometers in length, suggesting the heterogeneity of CCO activity even in the same fiber.
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ranking = 2.5
keywords = chronic progressive
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8/11. Partial cytochrome oxidase deficiency without subsarcolemmal accumulation of mitochondria in chronic progressive external ophthalmoplegia.

    Chronic progressive external ophthalmoplegia (CPEO) associated with proximal myopathy and/or craniosomatic abnormalities is a rare syndrome in which morphological mitochondrial changes have been found in some fibres (subsarcolemmal accumulation of mitochondria or "ragged red" fibres). We report a 14-year-old boy with CPEO and a mild proximal myopathy without these characteristic "ragged red" fibres. Histochemistry of skeletal muscle showed a mosaic of fibres without detectable cytochrome oxidase activity, while other mitochondrial enzymes were normal. The total cytochrome oxidase activity and cytochrome aa3 concentration in muscle mitochondrial fractions were only 40% of normal. This case is unique in that a biochemical defect was not accompanied by morphological abnormalities and may represent an early stage of CPEO before the development of morphological changes, or alternatively, a new variant of the disease.
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ranking = 2
keywords = chronic progressive
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9/11. A partial deficiency of cytochrome c oxidase in chronic progressive external ophthalmoplegia.

    A partial deficiency of cytochrome oxidase has been found in 7 patients with chronic progressive external ophthalmoplegia and proximal myopathy or craniosomatic abnormalities. Muscle biopsies from all these patients showed morphological mitochondrial abnormalities ("ragged red" fibres) and cytochemical assay of cytochrome oxidase showed that these fibres contained no demonstrable enzyme activity. The incidence of cytochrome oxidase-negative fibres was greater than that of "ragged-red" fibres suggesting that the enzyme defect preceded the development of morphological mitochondrial changes. Biochemical analysis of skeletal muscle mitochondrial fractions from 3 patients revealed in 1 case a significantly lower concentration of cytochrome aa3 and a decreased ratio of cytochrome oxidase/succinate-cytochrome c reductase. fasting blood metabolites were elevated in 2 patients. We suggest that partial cytochrome oxidase deficiency is the underlying defect in mitochondrial myopathy associated with the oculocraniosomatic syndromes.
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ranking = 2.5
keywords = chronic progressive
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10/11. The mitochondrial dna transfer RNALeu(UUR) A-->G(3243) mutation. A clinical and genetic study.

    The mitochondrial tRNALeu(UUR) A-->G(3243) mutation was identified in 22 unrelated patients. The probands and their relatives were assessed clinically and by quantitative mitochondrial dna (mtDNA) analysis. While 10 probands had clinical features consistent with the syndrome of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS), usually associated with this mutation, 12 probands had other phenotypes including other encephalopathies, chronic progressive external ophthalmoplegia (CPEO), myoclonic epilepsy and ragged red fibres (MERRF), myopathy alone and diabetes and deafness. Histochemical analyses of muscle biopsies showed a higher proportion of cytochrome oxidase (COX) negative fibres, but fewer strongly COX reactive fibres, in patients with CPEO compared with those with MELAS. The proportion of mutant mtDNA present in blood was significantly greater in symptomatic than asymptomatic subjects, and was correlated with age in both. This correlation was not observed in patients with the tRNALys A-->G(8344) mutation. The proportion of mutant mtDNA A-->G(3243) in muscle was always greater than that in blood. Significant correlations between proportion of mutant mtDNA in blood and both age of onset of disease and a clinical severity score were observed. However, the proportion of mutant mtDNA in blood in affected and unaffected cases overlapped, preventing use of the genetic-clinical correlation for prognostic or predictive purposes. The presence of intrafamilial clustering of phenotypes and the imperfect relationship between proportion of mutant mtDNA and the presence or absence of disease suggests that other factors may determine the phenotype. To investigate this possibility further, the tRNALeu(UUR) gene was sequenced in 23 probands and six relatives. In 28 patients the sequence was normal apart from the 3243 mutation, but in members of one family there was a homoplasmic T-->C transition at position 3290 which was not found in 140 controls or 50 other patients with mitochondrial myopathy. The family with this transition had high levels of mutant mtDNA A-->G(3243), with a unique phenotype of predominant skeletal myopathy, suggesting that this second base change in tRNALeu(UUR) may influence the clinical phenotype.
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ranking = 0.5
keywords = chronic progressive
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