A 20-year-old man comes to the emergency department with painful
muscle spasms. He notices that these episodes worsen after a run and seem to improve after brief periods of rest. His past medical history includes a right knee
ACL tear. His temperature is 37.0°C (98.6°F),
pulse is 80/min, respirations are 16/min, and
blood pressure is 125/75 mmHg. Abdominal examination is unremarkable. Rapid fingerstick glucose is 80 mg/dL. Serum creatine kinase levels are elevated. Laboratory investigations are shown below:
Serum |
Sodium | 140 mEq/L |
Potassium | 4 mEq/L |
Creatinine | 1.3 mg/dL |
Creatine kinase | 645 U/L |
Urine |
BUN/Cr | <15 |
Blood | Positive |
Erythrocytes | 0/hpf |
Leukocytes | 2/hpf |
Fractional excretion of sodium (FENa) | >2% |
Electrocardiogram and echocardiogram are unremarkable. Which of the following is the most likely diagnosis?