A 29-year-old male presents to the emergency department with complaints of
dark-colored urine, generalized fatigue, myalgias, and weakness after com-
pleting a marathon. The patient states that this was his first marathon. He has
no significant medical history and denies any medications or drug use. On
examination, he appears moderately ill and is afebrile with normal vital signs.
Physical exam reveals diffuse musculoskeletal tenderness. Urinalysis revealed
large amounts of blood (hemoglobin and myoglobin), and serum creatine
phosphokinase (CPK) was significantly elevated, as well as the potassium
level on his electrolytes. The serum lactate level was markedly elevated.
What is the most likely diagnosis?
What is the most appropriate treatment?
What is the biochemical basis for the markedly elevated serum