Differential Diagnosis for Elevated WBC with No Apparent Cause

Single Most Likely Diagnosis

• Viral infection: Many viral infections can cause a transient elevation in white blood cell (WBC) count without any other overt symptoms. This is often due to the body's immune response to the virus.

Other Likely Diagnoses

• Bacterial infection: Early stages of bacterial infections can present with elevated WBC counts before other symptoms become apparent.
• Inflammatory conditions: Conditions like rheumatoid arthritis, lupus, or other autoimmune diseases can cause an elevation in WBC count due to chronic inflammation.
• Stress or exercise: Physical stress or intense exercise can lead to a temporary increase in WBC count.
• Medication effect: Certain medications, such as corticosteroids, can cause an increase in WBC count.

Do Not Miss Diagnoses

• Leukemia: Although less common, leukemia (e.g., chronic lymphocytic leukemia, chronic myeloid leukemia) can present with an elevated WBC count without other symptoms. Missing this diagnosis could be catastrophic.
• Lymphoma: Similar to leukemia, lymphoma can cause an elevated WBC count and would be critical not to miss.
• Sepsis: In its early stages, sepsis might only present with an elevated WBC count. It is crucial to identify and treat sepsis promptly to prevent severe outcomes.

Rare Diagnoses

• Myeloproliferative neoplasms: Conditions like polycythemia vera, essential thrombocythemia, or primary myelofibrosis can cause an elevated WBC count but are less common.
• Parasitic infections: Certain parasitic infections, though rare in many parts of the world, can cause an elevation in WBC count.
• Adrenal insufficiency: In some cases, adrenal insufficiency can lead to an increase in WBC count, though this is not a common presentation.