History
Consider the following in the history:
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Age at onset of symptoms depends on enzyme activity levels. Initial symptoms are cramps, fatigue, and pain after exercise. [7]
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Because severity depends on enzyme activity, individual presentation is unique.
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The rate of rise in oxygen consumption per unit time (VO2) is relative to work rate increases.
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Some adults develop a progressive proximal weakness.
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Some adults develop a fixed motor weakness.
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The disorder has a unique "second-wind" phenomenon. [8] If a patient nearing fatigue slows exercise to a tolerable level, a point exists at which exercise may be increased again without previous symptoms [9] . According to Porcelli and colleagues, this phenomenon may be secondary to increased adrenergic response to exercise, influx of glucose, free fatty acids, and other substrates for muscle metabolism. [10]
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Burgundy-colored urine is usually reported in patients but is not always present. It is thought to be a result of rhabdomyolysis after intense exercise.
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Jones and colleagues report an unusual presentation of atypical chest pain and chronic troponinemia associated with hypertrophic cardiomyopathy among family members. [11]
Physical Examination
Physical examination is usually unremarkable in most patients. About 25% of patients may present with evidence of muscle hypertrophy. Proximal muscle wasting and weakness may be seen older patients. [5]
Consider the following in the physical examination:
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Diagnosis is suggested by patient history.
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Clinical findings may be absent upon physical examination.
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Muscle strength and reflexes may be normal.
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In later adult life, persistent weakness and muscle wasting may be present.
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When clinical suspicion is present, diagnostic testing includes the ischemic forearm test, laboratory analysis, and electromyography.
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About 10% of patients with GSD V may present with acute renal failure. [5]
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Metabolic pathways of carbohydrates.
