Differential Diagnosis for Elevated B12

Elevated vitamin B12 levels can be caused by various conditions. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Recent B12 Injection or Supplement: The most common reason for elevated B12 levels is recent ingestion or injection of vitamin B12 supplements. This is because the body stores excess B12 in the liver, and high doses can lead to elevated serum levels.

• Other Likely Diagnoses

  • Myeloproliferative Disorders: Conditions like polycythemia vera, essential thrombocytosis, and chronic myeloid leukemia can lead to increased production of B12-binding proteins, resulting in elevated B12 levels.
  • Liver Disease: Certain liver conditions, such as liver cirrhosis or hepatitis, can cause an increase in B12 levels due to the release of stored B12 from damaged liver cells.
  • Kidney Disease: Renal failure can lead to elevated B12 levels due to decreased excretion of the vitamin.

• Do Not Miss Diagnoses

  • Leukemia: Although less common, certain types of leukemia, such as acute myeloid leukemia (AML), can cause elevated B12 levels. Missing this diagnosis could be catastrophic.
  • Lymphoma: Some lymphomas can produce B12-binding proteins, leading to elevated levels. Early detection is crucial for effective treatment.

• Rare Diagnoses

  • Transcobalamin II Deficiency: A rare genetic disorder that affects the transport of B12, leading to elevated levels.
  • Gastric Carcinoma: Some cases of stomach cancer can produce B12-binding proteins, resulting in elevated B12 levels.
  • Folate Deficiency: Although folate and B12 are closely related, a deficiency in folate can sometimes lead to elevated B12 levels due to decreased utilization of B12.