Differential Diagnosis for Acute Anemia with Negative Hemolysis Workup and Elevated CPK with Muscle Pains

• Single Most Likely Diagnosis

  • Rhabdomyolysis: This condition is characterized by the breakdown of muscle tissue, leading to the release of muscle fiber contents into the blood. These contents include myoglobin, which can cause kidney damage, and CPK (creatine phosphokinase), an enzyme found in the heart, brain, and skeletal muscle. The elevated CPK levels and muscle pains in the patient are highly suggestive of rhabdomyolysis. Acute anemia could result from the significant fluid shifts and potential kidney injury associated with rhabdomyolysis.

• Other Likely Diagnoses

  • Trauma or severe muscle injury: Direct trauma to muscles can cause significant muscle damage, leading to elevated CPK levels and muscle pain. If the trauma is severe enough, it could also lead to acute anemia due to blood loss or significant tissue damage.
  • Polymyositis or dermatomyositis: These are inflammatory muscle diseases that can cause muscle weakness and pain. While they might not directly cause acute anemia, the inflammation and muscle damage could potentially lead to elevated CPK levels and, in severe cases, contribute to anemia through chronic disease mechanisms.
  • Severe exertional rhabdomyolysis: Similar to rhabdomyolysis, but specifically caused by intense physical exertion, leading to muscle breakdown, elevated CPK, and potentially acute anemia.

• Do Not Miss Diagnoses

  • Compartment syndrome: A condition where pressure within the muscles builds to dangerous levels, cutting off blood flow and leading to muscle and nerve damage. It can cause severe muscle pain, elevated CPK, and potentially lead to acute anemia if not promptly treated. Missing this diagnosis could result in permanent muscle damage or even loss of the affected limb.
  • Acute kidney injury: While not a direct cause of anemia, acute kidney injury can result from rhabdomyolysis and lead to a buildup of toxins, including those that could exacerbate anemia. It's crucial to identify and manage kidney injury promptly to prevent further complications.

• Rare Diagnoses

  • McArdle disease (Glycogen storage disease type V): A rare genetic disorder that affects the muscle cells' ability to break down glycogen for energy. It can lead to muscle cramps, weakness, and elevated CPK levels after exercise but is less likely to cause acute anemia directly.
  • Statin-induced rhabdomyolysis: Although rare, the use of statin drugs can, in some cases, lead to rhabdomyolysis, especially when combined with other medications or in patients with certain risk factors. This would present with muscle pain, elevated CPK, and potentially acute anemia.