Glycogen storage disease type v

Glycogen storage disease type V (GSD V), also known as McArdle's disease, is a metabolic disorder characterized by a deficiency in the enzyme myophosphorylase. This enzyme is essential for the breakdown of glycogen in muscle cells, and its deficiency leads to the accumulation of glycogen in these cells, causing various symptoms.

Etiology

GSD V is caused by mutations in the PYGM gene, which provides instructions for making myophosphorylase. The mutations in this gene reduce or eliminate the activity of this enzyme, preventing the breakdown of glycogen in muscle cells. This disease is inherited in an autosomal recessive manner, meaning both copies of the gene in each cell have mutations.

Symptoms

The symptoms of GSD V typically begin in childhood or adolescence, although they can appear later in life. They include exercise intolerance, muscle weakness, muscle cramps, and fatigue. In severe cases, vigorous exercise can lead to rhabdomyolysis, a condition that can cause kidney damage.

Diagnosis

The diagnosis of GSD V is based on the symptoms, a physical examination, and specialized tests. These tests may include a muscle biopsy, which can reveal an excess of glycogen in muscle cells, and genetic testing, which can identify mutations in the PYGM gene.

Treatment

There is currently no cure for GSD V. Treatment is aimed at managing the symptoms and may include a high-protein diet, regular, moderate exercise, and avoiding strenuous activity. In some cases, medications may be used to manage symptoms.

Epidemiology

GSD V is a rare disease, affecting approximately 1 in 100,000 people. It occurs in all ethnic groups, but is more common in individuals of Northern European descent.

See also

• Glycogen storage disease
• Metabolic disorder
• Rhabdomyolysis

NIH genetic and rare disease info

• NIH info on Glycogen storage disease type v

Glycogen storage disease type v is a rare disease.