Which finding is most characteristic of infectious mononucleosis?

• A. Splenomegaly
• B. Jaundice
• C. Chronic cough
• D. Weight gain

Answer: (A)

Splenomegaly stands out in infectious mononucleosis because EBV-driven immune activation causes the spleen to enlarge as part of the systemic lymphoid response. This enlargement is a hallmark finding and carries important safety implications, since the enlarged spleen is at risk of rupture with trauma, so kids are often advised to avoid contact sports for several weeks. Jaundice can occur if there is liver involvement, but it is not as characteristic. A chronic cough suggests a respiratory infection or asthma, and weight gain is not typical of mono. So the presence of an enlarged spleen best fits the condition.