Reverse fiber type disproportion: A distinct metabolic myopathy

Cooper, Christopher B.; Dolezal, Brett A.; Riley, M.; Verity, M. Anthony; Shieh, Perry B.

doi:10.1002/mus.24984

Cited by 3 publications

(3 citation statements)

References 17 publications

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“…Studies of lactate responses to maximum exercise in patients with myopathy show divergent results. Exaggerated lactate increases have been observed in a variety of muscle diseases, including inherited mitochondrial myopathy 20 and type II fiber predominance, 5 which may be due to inadequate ATP regeneration via oxidative metabolism in the muscle. 21 By contrast, 1 study showed reduced lactate levels at maximum exercise in individuals with mitochondrial myopathy.…”

Section: Figurementioning

confidence: 99%

“…These conditions have been associated with mild to moderately elevated serum CK levels, although no direct relationship to future myopathy development has been established . Other subjects from our database with elevated CK had biopsy‐diagnosed mitochondrial myopathy or type II fiber predominance . Still others had no notable symptoms apart from generalized myalgia and fatigue.…”

mentioning

confidence: 95%

“…[2][3][4] Other subjects from our database with elevated CK had biopsy-diagnosed mitochondrial myopathy or type II fiber predominance. 5 Still others had no notable symptoms apart from generalized myalgia and fatigue. Case reports describing elevated CK levels as a precedent to the diagnosis of distal myopathy suggest the possibility of asymptomatic CK elevation as an early indicator of the development of other myopathies as well.…”

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confidence: 99%

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Exercise responses in patients with chronically high creatine kinase levels

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Exercise responses in patients with chronically high creatine kinase levels

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Congenital fiber-type disproportion in an ambulatory rehabilitation setting

Palma

Kéilani

Hasenoehrl

et al. 2017

Wien Med Wochenschr

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Congenital fiber-type disproportion is a rare condition, histologically characterized by a relative type 1 fiber hypotrophy. The main clinical feature is mild-to-severe muscle weakness. In this report, we present the case of a 21-year-old patient with congenital fiber-type disproportion in an outpatient rehabilitative setting to evaluate the feasibility and results of an assessment battery, including bioimpedance analysis (BIA), dynamometry, 3D gait analysis, 6‑min walk test (6MWT), and the timed up and go test (TUG). The patient had a notable decrease in all functional scores. BIA: lean body mass, 38.4 kg (50.2 ± 5.3), body fat, 1.6% (12.4 ± 4.4); hand dynamometry: 18.5 kg left/20.0 kg right (44.8 ± 6.6); walking speed, 58 cm/s (122.7 ± 11.1), step length, 43.0 cm (61.6 ± 3.5); 6MWT: 478.5 m (638 ± 44); TUG: 9.4 s (8.1 ± 1.0). No adverse events were reported. The tests used were easily applicable in clinical routine and well tolerated by our patient.

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Cardiopulmonary Exercise Testing and Metabolic Myopathies

2017

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Skeletal muscle requires a large increase in its ATP production to meet the energy needs of exercise. Normally, most of this increase in ATP is supplied by the aerobic process of oxidative phosphorylation. The main defects in muscle metabolism that interfere with production of ATP are (1) disorders of glycogenolysis and glycolysis, which prevent both carbohydrate entering the tricarboxylic acid cycle and the production of lactic acid; (2) mitochondrial myopathies where the defect is usually within the electron transport chain, reducing the rate of oxidative phosphorylation; and (3) disorders of lipid metabolism. Gas exchange measurements derived from exhaled gas analysis during cardiopulmonary exercise testing can identify defects in muscle metabolism because [Formula: see text]o and [Formula: see text]co are abnormal at the level of the muscle. Cardiopulmonary exercise testing may thus suggest a likely diagnosis and guide additional investigation. Defects in glycogenolysis and glycolysis are identified by a low peak [Formula: see text]o and absence of excess [Formula: see text]co from buffering of lactic acid by bicarbonate. Defects in the electron transport chain also result in low peak [Formula: see text]o, but because there is an overreliance on anaerobic processes, lactic acid accumulation and excess carbon dioxide from buffering occur early during exercise. Defects in lipid metabolism result in only minor abnormalities during cardiopulmonary exercise testing. In defects of glycogenolysis and glycolysis and in mitochondrial myopathies, other features may include an exaggerated cardiovascular response to exercise, a low oxygen-pulse, and excessive ammonia release.

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Reverse fiber type disproportion: A distinct metabolic myopathy

Cited by 3 publications

References 17 publications

Exercise responses in patients with chronically high creatine kinase levels

Exercise responses in patients with chronically high creatine kinase levels

Congenital fiber-type disproportion in an ambulatory rehabilitation setting

Cardiopulmonary Exercise Testing and Metabolic Myopathies

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