McArdle's disease is associated with a deficiency in which enzyme?

McArdle's disease, also known as glycogen storage disease type V, is primarily caused by a deficiency in glycogen phosphorylase, the enzyme responsible for breaking down glycogen into glucose-1-phosphate during glycogenolysis. In individuals with McArdle's disease, this deficiency results in an inability to effectively mobilize glucose from glycogen stores, particularly during periods of intense exercise. As a consequence, affected individuals may experience symptoms such as muscle cramps, fatigue, and exercise intolerance due to a lack of available energy.

Glycogen phosphorylase operates in skeletal muscles, and its deficiency leads to an accumulation of glycogen in the muscle tissues, which do not get adequately utilized for energy during physical activity. This condition specifically highlights how enzymatic deficiencies in glycogen metabolism can manifest as notable clinical syndromes, reinforcing the importance of understanding metabolic pathways in pathology.

In summary, the correct answer is tied to the specific enzymatic deficiency that characterizes McArdle's disease, emphasizing the role of glycogen phosphorylase in energy mobilization and the physiological repercussions of its absence.