MS-2447

A 9-year-old boy visits his pediatrician with his parents, complaining of blood in his urine. He recently started playing basketball and noticed the red urine after a game. The patient reports experiencing painful leg cramps during games, but he pushes through them to continue playing. He never sought medical attention for the cramps, assuming they were due to lack of training. This is the first time he has experienced these symptoms. The boy is referred for a test to check for a deficiency in a specific muscle enzyme that may be causing his presentation. What is the most likely diagnosis for this patient?