What are the causes of rhabdomyolysis and elevated creatine kinase?

Causes of Rhabdomyolysis and Elevated CK

Rhabdomyolysis and elevated creatine kinase result from skeletal muscle breakdown triggered by acquired factors (trauma, medications, toxins, infections, metabolic derangements) or inherited disorders (glycogen metabolism defects, fatty acid oxidation disorders, mitochondrial diseases, structural myopathies). 1, 2

Acquired Causes

Medications and Toxins

• Statins are the most clinically relevant drug cause, with myopathy occurring in 0.1%-1% of patients and rhabdomyolysis in 0.04%-0.2% 3
• Risk increases dramatically with drug interactions involving cytochrome P-450 3A4 (cyclosporine, fibrates, macrolide antibiotics, certain antifungals, niacin) 4
• Fatal rhabdomyolysis with statins is exceedingly rare (<1 death per million prescriptions) 4
• Substance abuse and illicit drugs 2
• Toxic exposures 2

Physical and Traumatic

• Direct or indirect trauma 1
• High-intensity exercise, particularly after prolonged inactivity 5, 6
• Immobilization 7

Medical Conditions

• Sepsis and infections 7
• Electrolyte abnormalities 2
• Endocrine disturbances 2, 8
• Autoimmune myopathies 2
• Alcohol use 7

Inherited Causes

Consider genetic testing when patients meet RHABDO criteria: 9

• Recurrent episodes of exertional rhabdomyolysis
• HyperCKemia persisting >8 weeks after event (p=0.0081 for genetic cause)
• Accustomed physical exercise triggers symptoms
• Blood CK >50x ULN
• Drug/medication cannot sufficiently explain severity
• Other family members affected or presence of myalgia (p=0.028), objective weakness (p=0.049), or parental consanguinity (p=0.0090)

Specific Genetic Disorders 2, 9

• Glycogen metabolism disorders (PYGM - most frequent in Brazilian cohort)
• Fatty acid β-oxidation defects (CPT II, ACADS, ACADM)
• Mitochondrial oxidative phosphorylation disorders
• Structural myopathies (ANO5, DYSF, FKTN)
• Channelopathies
• Sickle-cell disease

Key Clinical Pitfalls

Atypical Presentations

Some patients present without classic triad of muscle pain, weakness, and dark urine 5. Watch for:

• Limb swelling and asthenia alone
• Modest CK elevation that persists 1-3 months despite treatment
• Slow response to aggressive fluid therapy

Laboratory Considerations

• CK elevation can occur without electrolyte abnormalities or renal failure 6
• Typical CK:AST ratio is 20:1, but severe cases may show ratios >100:1 6
• Persistent CK elevation >8 weeks strongly suggests genetic etiology 9

Statin-Related Nuances

• Muscle complaints occur in ~5% of both statin and placebo groups in trials, suggesting many are non-specific 4
• Pre-existing conditions (spinal stenosis, polyradiculopathy) should not exclude statin-associated worsening 3
• Normal CK does not rule out statin myopathy 3

Diagnostic Approach

When evaluating elevated CK or suspected rhabdomyolysis:

1. Identify and remove triggering factors immediately 1
2. Assess severity: CK level, renal function, electrolytes, myoglobinuria
3. Determine acquired vs. inherited: Apply RHABDO criteria if CK ≥5x ULN without clear exogenous cause 9
4. Pursue genetic testing if persistent hyperCKemia >8 weeks, myalgia, weakness, or family history present 9

Monogenic causes account for nearly half of cases after proper exclusion of exogenous etiologies 9.