Which of the following is a characteristic of infectious mononucleosis?

• A. Presence of atypical lymphocytes in the blood
• B. Production of a toxin that inhibits protein synthesis
• C. Formation of a pseudomembrane in the throat
• D. Development of a bull's-eye rash at the site of infection

Answer: (A)

Verified step by step guidance

1. Understand the nature of infectious mononucleosis, which is a viral infection primarily caused by the Epstein-Barr virus (EBV). It mainly affects lymphocytes, a type of white blood cell.
2. Recall that infectious mononucleosis is characterized by an immune response involving atypical lymphocytes, which are larger and have an irregular shape compared to normal lymphocytes.
3. Review the options given: production of a toxin that inhibits protein synthesis is typical of some bacterial infections (e.g., diphtheria), formation of a pseudomembrane in the throat is also associated with diphtheria, and development of a bull's-eye rash is characteristic of Lyme disease.
4. Recognize that the hallmark laboratory finding in infectious mononucleosis is the presence of atypical lymphocytes in the blood, which reflects the body's immune response to the viral infection.
5. Conclude that the correct characteristic of infectious mononucleosis among the options is the presence of atypical lymphocytes in the blood.