A 19-year-old man presents to the clinic complaining of early fatigue and muscle cramps while playing sports. He is fine when walking or doing less intense levels of work. On physical examination, he appears well and the vital signs are normal. Muscle bulk, tone and strength in the proximal muscles are normal. There is no muscle fatigue with repetitive arm grip exercises. After an exercise stress test, his serum creatine kinase (CK) is elevated and lactate level is normal. Which of the following is the most likely diagnosis?
High-Yield Explanation
There are many types of glycogen storage diseases, each caused by a different enzymatic abnormality. The best-known types of glycogen storage disease are those that have hepatic hypoglycemic pathophysiology (eg, von Gierke disease) or those that have muscle energy pathophysiology (McArdle disease). InMcArdle' symptoms usually develop in adulthood, and it is marked by cramps and muscle injury with strenuous exercise, but not with usual activities. Gaucher and Tay-Sachs disease are lysosomal storage diseases.