Differential Diagnosis for Elevated CK in a 56-year-old Male

The patient presents with an elevated creatine kinase (CK) level of 206, accompanied by a complaint of right knee pain and a history of mild osteoarthritis in the same knee. Considering the patient's medical history, including hypertension (HTN), type 2 diabetes mellitus (TIIDM), myocardial infarction (MI) with percutaneous coronary intervention (PCI) using drug-eluting stents (DES), and atorvastatin therapy, the following differential diagnoses are proposed:

• Single Most Likely Diagnosis
  • Muscle strain or injury: Given the patient's complaint of right knee pain and the presence of mild osteoarthritis, a muscle strain or injury around the knee could easily explain the elevated CK level. Physical activity or minor trauma could lead to muscle damage, releasing CK into the bloodstream.
• Other Likely Diagnoses
  • Statins-induced myopathy: Atorvastatin, an HMG-CoA reductase inhibitor, is known to cause myopathy as a side effect, although it is rare. The high dose of 80 mg daily increases the risk. The patient's symptoms and elevated CK could be indicative of statin-induced muscle damage.
  • Osteoarthritis flare: While osteoarthritis itself does not typically cause significant elevations in CK, a severe flare could potentially lead to muscle injury around the affected joint due to increased stress and strain on the surrounding muscles, thereby elevating CK levels.
• Do Not Miss Diagnoses
  • Rhabdomyolysis: Although less likely, rhabdomyolysis is a serious condition that requires immediate attention. It involves the breakdown of muscle tissue and can be caused by severe muscle injury, certain medications (including statins), or other factors. The presence of dark urine, severe muscle pain, and significantly elevated CK levels would suggest this diagnosis.
  • Acute coronary syndrome: Given the patient's history of MI and PCI, it is crucial not to miss an acute coronary syndrome (ACS), which could potentially cause an elevation in CK, especially if there is myocardial damage. However, CK-MB would be more specific for myocardial injury.
• Rare Diagnoses
  • Polymyositis or dermatomyositis: These are inflammatory muscle diseases that could cause elevated CK levels. They are less common and would typically present with more systemic symptoms, including skin rash (in dermatomyositis), proximal muscle weakness, and possibly other autoimmune features.
  • McArdle disease: A rare genetic disorder affecting the muscle's ability to break down glycogen, leading to muscle cramps and elevated CK levels after exercise. It is unlikely but should be considered in the differential diagnosis of unexplained CK elevations, especially if the patient reports cramps or myalgias after physical activity.

Each of these diagnoses should be considered in the context of the patient's overall clinical presentation, and further diagnostic testing or consultation with specialists may be necessary to determine the underlying cause of the elevated CK level.