Differential Diagnosis for High CK with Muscle Weakness and No Other Symptoms

• Single Most Likely Diagnosis
  • Muscular dystrophy: This is a group of inherited disorders characterized by progressive muscle weakness and high creatine kinase (CK) levels. The lack of other symptoms makes this a plausible diagnosis, as muscular dystrophy can present with isolated muscle weakness and elevated CK.
• Other Likely Diagnoses
  • Polymyositis: An inflammatory muscle disease that can cause muscle weakness and elevated CK levels. The absence of other symptoms like skin rash or fever does not rule out this diagnosis, as presentations can vary.
  • Dermatomyositis: Similar to polymyositis but often includes skin manifestations. Although the question specifies no other symptoms, some cases might have subtle or overlooked skin signs, making this a consideration.
  • Toxic myopathy: Certain drugs and toxins can cause muscle damage, leading to high CK levels and muscle weakness. This could be a likely diagnosis if the patient has been exposed to such substances.
• Do Not Miss Diagnoses
  • Rhabdomyolysis: A serious condition involving the breakdown of muscle tissue, which can lead to kidney failure. It is crucial to identify this condition early, even though it often presents with more severe symptoms like myalgia and dark urine.
  • McArdle disease: A genetic disorder affecting the muscle's ability to break down glycogen, leading to muscle weakness and high CK levels after exercise. Missing this diagnosis could lead to inappropriate exercise advice or misunderstanding of the patient's condition.
• Rare Diagnoses
  • Mitochondrial myopathies: A group of disorders affecting the mitochondria, leading to muscle weakness and other symptoms. These conditions are rare and might not always present with high CK levels, but they should be considered in the differential diagnosis, especially if other tests are inconclusive.
  • Inclusion body myositis: The most common acquired myopathy in adults over 50, characterized by progressive muscle weakness and wasting. It is rare and often has a slower progression, which might not always correlate with significantly elevated CK levels at the outset.