When do splenic ruptures commonly occur in the course of mononucleosis?

Splenic ruptures in the context of infectious mononucleosis are most commonly associated with the first three weeks of the illness. This time frame coincides with the period when the spleen is most engorged and vulnerable due to the response to the Epstein-Barr virus. The spleen plays a significant role in the immune response, and during this acute phase of mononucleosis, it can become enlarged (splenomegaly), increasing the risk of rupture, especially with activities that put stress on it, such as contact sports or even minor trauma.

In the later weeks of the condition or after recovery, the risk of splenic rupture significantly decreases as the spleen returns to its normal size and the inflammatory process resolves. Therefore, understanding the pathophysiology of splenic involvement during the acute phase helps clarify why the initial three weeks are critical for monitoring the potential risk of splenic rupture in patients with infectious mononucleosis.