A patient presents with splenomegaly, fatigue, and LAD. Pt reveals she has had a sore throat for 2 weeks. What might we see on a blood smear?

• A. Neutrophils
• B. Platelets
• C. Large lymphocytes
• D. Erythrocytes

Answer: (C)

This question hinges on recognizing infectious mononucleosis caused by EBV. The hallmark blood finding is a lymphocytosis with atypical, large activated lymphocytes—CD8+ T cells responding to EBV-infected B cells. On a smear, these appear as large lymphocytes with irregular nuclei and abundant cytoplasm (often called atypical or Downey cells). This fits the patient's presentation of sore throat, fatigue, lymphadenopathy, and splenomegaly. Neutrophils or erythrocytes aren’t the characteristic finding in mono, and platelets aren’t the defining feature.