What examination finding can help differentiate infectious mononucleosis from streptococcal pharyngitis?

Infectious mononucleosis, commonly caused by Epstein-Barr virus, typically presents with distinctive clinical features. One of these hallmark findings is bilateral posterior cervical lymphadenopathy. This is in contrast to streptococcal pharyngitis, which usually has a different lymphadenopathy pattern.

In infectious mononucleosis, patients often exhibit a more generalized and symmetric enlargement of lymph nodes, particularly in the posterior cervical chain, due to the immune response triggered by the viral infection. This finding, therefore, serves as a key differentiator from streptococcal throat infections, which tend to show lymphadenopathy that is less consistently bilateral and may sometimes be more localized in nature.

In addition, other features such as fever and tonsillar enlargement can be present in both conditions, making them less reliable for differentiation. The presence of purulent tonsils, which suggests bacterial infection, is more aligned with streptococcal pharyngitis rather than infectious mononucleosis. However, the unique characteristic of bilateral posterior cervical lymphadenopathy remains a strong indicator for identifying infectious mononucleosis in a clinical setting.