McArdle's Disease

 

Welcome to PT 635 Pathophysiology of Complex Patient Problems This is a wiki created by and for the students in the School of Physical Therapy at Bellarmine University in Louisville KY. Please do not edit unless you are involved in this project, but please come back in the near future to check out new information!!

Original Editors - Ed Foring from Bellarmine University's Pathophysiology of Complex Patient Problems project.

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Definition/Description

In 1951 Dr. Brain McArdle of Guy's Hospital in London England first described this disease. This disease also is refered to as myophosphorylase deficiency or Type V glycogen storage disease. This disease is a metabolic disease where skeletal muscle cells can not breakdown glycogen into glucose.

Prevalence

McArdle's disease is rare affecting approximately 1 in 100,000 people. This disease remains undiagnosis until most reach adulthood therefore the prevalence of this disease may be higher.

Characteristics/Clinical Presentation

Symptoms typically present 10 seconds after strenous exercise has begun. After 10 seconds of exercise skeletal muscle relies on the conversion of glycogen to glucose to produce ATP which is the main energy source to power muscular contraction.

Premature Exhaustion: Skeletal muscles inability to metabolize glycogen into glucose with strenous activity leads to an abrupt feeling of exhaustion or fatigue, with an increase in heart rate.

Muscle Failure: This particularly occurs under extreme stress where the muscle no longer can produce contraction regardless of the effort made. This is compaired to "wall" runners experience when doing a marathon.

Cramping: Muscle failure leads to electrically-silent contractures which are very painful and can lead to muscle damage.

Myoglobinuria: Damage to muscle tissue leads to the release of proteins,creatine kinase and myoglobin, into the blood which are than excerted with urination. These proteins are iron-rich and may cause urine to be a redish color. Myoglobinuria has lead to renal dysfunction, therefore cramping and muscle failure episodes require medical attention.

Fixed Weakness: Muscle damage caused by rhabdomyolysis can lead to muscle weakness that seems to not get physically stronger or is extremely difficult to make strength gains.

Second Wind: The phenomenon has been observed in clincal trials in patients after following a "warm up" period. This second wind does not relieve failure symptoms for intense exercise but offers some relief for light to moderate exercise.

Associated Co-morbidities

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Medications

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Diagnostic Tests/Lab Tests/Lab Values

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Etiology/Causes

The cause of this disease is due to a missing or non-functioning enzyme that breaks down glycogen into glucose during exercise called myophosphorylase C. Several genetic mutations have been found to be the reason why this enzyme is missing or non-functioning.

Systemic Involvement

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Medical Management (current best evidence)

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Physical Therapy Management (current best evidence)

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Alternative/Holistic Management (current best evidence)

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Differential Diagnosis

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Case Reports/ Case Studies

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Resources

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Recent Related Research (from Pubmed)

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References

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McArdlesDisease.org. www.mcardledisease.org (accessed 17 March 2011). 

Myoglobinuria. Wikidoc. http://www.wikidoc.org/index.php/Myoglobinuria (accessed 17 March 2011).