Glycogen storage disease type V

Editor-In-Chief: Prab R Tumpati, MD
Obesity, Sleep & Internal medicine
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Glycogen storage disease type V
Synonyms	McArdle's disease, Myophosphorylase deficiency
Pronounce
Specialty	Neurology, Genetics
Symptoms	Muscle pain, cramps, exercise intolerance, myoglobinuria
Complications	N/A
Onset	Childhood or early adulthood
Duration	Lifelong
Types	N/A
Causes	Genetic mutation in the PYGM gene
Risks	Family history of the condition
Diagnosis	Genetic testing, muscle biopsy, blood test
Differential diagnosis	Other glycogen storage diseases, muscle disorders
Prevention	N/A
Treatment	Dietary management, exercise therapy
Medication
Prognosis	Generally good with management
Frequency	Rare
Deaths

Glycogen Storage Disease Type V (also known as McArdle's Disease) is a rare genetic disorder characterized by a deficiency in the enzyme myophosphorylase. This enzyme is necessary for the breakdown of glycogen in muscle cells. The lack of this enzyme leads to symptoms such as muscle weakness and cramps.

Symptoms

The symptoms of Glycogen Storage Disease Type V typically begin in childhood or adolescence. They include:

• Muscle weakness
• Muscle cramps
• Exercise intolerance
• Fatigue
• Myoglobinuria (presence of myoglobin in urine)

Causes

Glycogen Storage Disease Type V is caused by mutations in the PYGM gene. This gene provides instructions for making the enzyme myophosphorylase, which is necessary for the breakdown of glycogen in muscle cells. When mutations occur in the PYGM gene, the enzyme's activity is reduced or eliminated, preventing the breakdown of glycogen and leading to the symptoms of the disease.

Diagnosis

Diagnosis of Glycogen Storage Disease Type V is typically made through a combination of clinical examination, laboratory testing, and genetic testing. The Forearm ischemic exercise test is a common diagnostic tool used to identify the disease.

Treatment

There is currently no cure for Glycogen Storage Disease Type V. Treatment is focused on managing symptoms and includes:

• Physical therapy
• Dietary modifications
• Avoidance of strenuous exercise

See also

• Glycogen storage disease
• Metabolic disorder
• Genetic disorder

External links

• GeneReviews: Glycogen Storage Disease Type V
• National Organization for Rare Disorders: Glycogen Storage Disease Type V

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