Differential Diagnosis for Elevated WBC and Vitamin B12 in a 53-year-old Female

Single Most Likely Diagnosis

• Vitamin B12 deficiency due to pernicious anemia: This condition is characterized by the deficiency of intrinsic factor, leading to impaired vitamin B12 absorption. It often presents with megaloblastic anemia, which can cause an elevated white blood cell (WBC) count due to the body's attempt to compensate for the anemia. The elevated vitamin B12 level might seem counterintuitive but could be due to recent supplementation or the body's release of stored vitamin B12 in response to the deficiency.

Other Likely Diagnoses

• Chronic myeloid leukemia (CML): CML can cause an elevated WBC count and may be associated with elevated vitamin B12 levels due to increased production by the leukemic cells.
• Myeloproliferative neoplasms (MPN): Conditions like polycythemia vera, essential thrombocythemia, and primary myelofibrosis can lead to elevated WBC counts and potentially affect vitamin B12 levels.
• Infection: Certain infections can cause both an elevated WBC count and alterations in vitamin B12 levels, either through direct effects on the bone marrow or through inflammation-induced changes in metabolism.

Do Not Miss Diagnoses

• Leukemia (acute or chronic): While less common, acute or other forms of leukemia must be considered due to their potential for rapid progression and the need for immediate treatment.
• Lymphoma: Both Hodgkin and non-Hodgkin lymphoma can present with elevated WBC counts and alterations in vitamin metabolism, including vitamin B12.
• Sepsis: In severe infections, sepsis can lead to significant alterations in WBC count and potentially affect vitamin levels, including vitamin B12, due to the systemic inflammatory response.

Rare Diagnoses

• Congenital disorders of vitamin B12 metabolism: These are rare genetic conditions that affect the body's ability to metabolize vitamin B12, potentially leading to elevated levels and associated hematological abnormalities.
• Vitamin B12-binding protein abnormalities: Certain rare conditions can affect the proteins that bind and transport vitamin B12, potentially leading to elevated levels and associated symptoms.
• Medication-induced changes: Certain medications can affect vitamin B12 levels and WBC counts, though this would be less common and dependent on the specific medication and patient factors.