Diagnosis, Etiology, Pathophysiology, and Complications of Rhabdomyolysis

A 28-year-old woman was admitted to the general internal medicine service with a 3-day history of malaise and cough that progressed to include myalgia, generalized weakness, and dark-colored urine. Three days before admission, she had an abrupt onset of a dry nonproductive cough, malaise, and anorexia that resulted in a prolonged period of fasting. On the second day of the illness, she awoke with diffuse muscle pain and progressive weakness, culminating in an inability to walk. She subsequently noted dark urine and presented to the emergency department, leading to this admission. She had no recent trauma, exercise, rash, joint pain, or foreign travel. She was taking a multivitamin supplement but no prescription medication.
At presentation, she was mildly distressed but oriented. Her vital signs were within normal limits, apart from mild tachycardia (heart rate, 104 beats/min). Physical examination revealed grade 3/5 limb muscle strength, although testing was associated with obvious discomfort. Muscle bulk and tone, tendon reflexes, and sensation were normal. Notably, there was no rash, and cardiorespiratory examination yielded unremarkable findings. Initial chest radiography revealed a left lower lobe infiltrate most consistent with pneumonia. Urinalysis was strongly positive for hemoglobin. Initial laboratory analysis (reference ranges provided parenthetically) revealed that her creatine kinase (CK) level was markedly elevated at 118,342 U/L (38-176 U/L).
1.What is the most appropriate next step to confirm the diagnosis of rhabdomyolysis in this patient? Provide an explanation for your answer.
2.What is the most likely etiology of this patient's recurrent rhabdomyolysis?
3.Rhabdomyolysis is a rapid breakdown of muscle. Detail the pathophysiology behind rhabdomyolysis.
4.What are the possible complications of rhabdomyolysis?
5.Which medications may cause rhabdomyolysis?