Complications

Complications of mononucleosis can sometimes be serious.

Enlargement of the spleen

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.

Liver issues

Problems with your liver also may occur:

• Hepatitis. You may experience mild liver inflammation (hepatitis).
• Jaundice. A yellowing of your skin and the whites of your eyes (jaundice) also occurs occasionally.

Less common complications

Mononucleosis can also result in less common complications, including:

• Anemia — a decrease in red blood cells and in hemoglobin, an iron-rich protein in red blood cells
• Thrombocytopenia — a low count of platelets, which are blood cells involved in clotting
• Heart problems — an inflammation of the heart muscle (myocarditis)
• Complications involving the nervous system — meningitis, encephalitis and Guillain-Barre syndrome
• Swollen tonsils — which can block breathing

The Epstein-Barr virus can cause much more serious illness in people who have impaired immune systems. People with weakened immune systems may include people with HIV/AIDS or people taking drugs to suppress immunity after an organ transplant.