Rhabdomyolysis

Description

• Breakdown of muscle and release of intracellular contents into the bloodstream
• Most commonly caused by traumatic muscle injury
• Typically presents with muscle pain, weakness, and reddish brown (tea-colored) urine
• Up to 50% of patients are asymptomatic.

Epidemiology

Most common among

• Males; <10 years old; >60 years old; BMI >40 kg/m³

Incidence

• 25,000 reported cases annually in the United States
• Although muscle-related side effects of statins are the most common reason for discontinuation of statins, rhabdomyolysis is only seen in 0.5% of patients.

Etiology and Pathophysiology

• Direct muscle trauma (most common cause)
  • Crush injuries; fractures; extended periods of muscle pressure (during surgery, unconscious from alcohol ingestion, coma); burns, electrocution, lightning strike
• Muscle exertion
  • New strenuous and/or prolonged physical exercise (marathon runners, athletes, contact sports); seizures; delirium tremens; malignant hyperthermia; neuroleptic malignant syndrome (NMS)
• Drugs and toxins
  • Alcohol; cocaine (most common recreational drug), methamphetamine, phencyclidine, heroin, bath salts (1)[B], and synthetic marijuana has been associated with severe rhabdomyolysis; antipsychotics (due to NMS, malignant hyperthermia, and dystonia); zidovudine; antimalarials; HMG-CoA reductase inhibitors (statins)—develops about 2 to 3 weeks after initiating therapy (risk <0.01%, elevated with higher doses and in combination with fibrates); colchicine; corticosteroids; carbon monoxide; snake envenomation; scorpion bites
• Muscle ischemia
  • Thrombosis, embolism, sickle cell disease; compartment syndrome; tourniquets
• Infections
  • Viral: influenza A and B, coxsackievirus, HIV, varicella
  • Bacterial: Streptococcus or Staphylococcus sepsis, gas gangrene, necrotizing fasciitis, Salmonella, Legionella
  • Malaria
• Hypothermia; hyperthermia
• Autoimmune disorders
  • Polymyositis, dermatomyositis
• Metabolic and endocrinologic:
  • Hypothyroidism or thyrotoxicosis; electrolyte imbalances (e.g., hyponatremia, hypernatremia, hypokalemia, hypocalcemia, hypophosphatemia); diabetic ketoacidosis; hyperosmolar state

Genetics
Hereditary causes of rhabdomyolysis are rare but should be suspected in children; patients with recurrent attacks; or patients who have attacks after minimal exertion, mild illness, or starvation.

• Genetic disorders
  • Muscular dystrophies; disorders of lipid metabolism (e.g., carnitine palmitoyltransferase deficiency)
  • Disorders of carbohydrate metabolism (i.e., phosphofructokinase deficiency, phosphoglycerate mutase, myophosphorylase deficiency, a.k.a. McArdle disease/deficiency); glycogen storage diseases (e.g., phosphorylase B kinase deficiency) and others (e.g., lactate dehydrogenase A deficiency, phosphofructokinase deficiency)
  • Mitochondrial disorders; sickle cell trait

General Prevention

• Avoid excessive exertion; ensure adequate hydration.
• Avoid precipitating drugs, metabolic and electrolyte abnormalities.