Mononucleosis may cause enlargement of the spleen. In extreme cases, your spleen may rupture, causing sharp, sudden pain in the left side of your upper abdomen. If such pain occurs, seek medical attention immediately — you may need surgery.

Why does mono affect your spleen?

Enlarged Spleen Mononucleosis can cause swelling in the spleen, which can raise the risk of a rupture of the organ if too much pressure is applied (something that might happen in a fall or from someone bumping into you, which is why doctors recommend avoiding strenuous activity and contact sports while recovering and …

How long does your spleen stay enlarged with mono?

A fever and sore throat may last for about two weeks. Muscle aches and fatigue may last for two to four weeks. An enlarged spleen may take up to eight weeks to go back to normal.