Differential Diagnosis for Elevated B12 with Normal CBC, Normal LFTs, and Non-Drinker

• Single Most Likely Diagnosis
  • Vitamin B12 Supplement Use: The most straightforward explanation for elevated B12 levels, especially in a non-drinker with otherwise normal lab results, is the use of vitamin B12 supplements. Many people take B12 supplements for energy or to prevent deficiency, which can easily lead to elevated levels.
• Other Likely Diagnoses
  • Recent Vaccination or Medication: Certain medications and vaccinations can transiently elevate B12 levels. For example, some vaccines and medications may contain cobalamin (B12) or affect its metabolism.
  • Gastrointestinal Conditions: Conditions like atrophic gastritis or gastric bypass surgery can lead to increased B12 absorption or utilization, potentially causing elevated levels.
  • Family History or Genetic Predisposition: Some individuals may have a genetic predisposition to elevated B12 levels due to variations in genes involved in B12 metabolism.
• Do Not Miss Diagnoses
  • Myeloproliferative Neoplasms (MPN): Although less common, MPNs such as polycythemia vera, essential thrombocytosis, or primary myelofibrosis can cause elevated B12 levels due to increased production of transcobalamin I by neutrophils. Missing this diagnosis could be critical due to the potential for thrombotic complications and transformation to acute leukemia.
  • Leukemia: Certain types of leukemia can lead to elevated B12 levels. Early detection is crucial for effective management and prognosis.
• Rare Diagnoses
  • Transcobalamin II Deficiency: A rare genetic disorder affecting the transport of vitamin B12, leading to elevated levels of B12 in the blood but deficiency within cells.
  • Liver Disease: Although the patient has normal LFTs, rare liver conditions could potentially affect B12 metabolism, leading to elevated levels. This would be an unusual presentation but should be considered if other explanations are ruled out.