Causes

A number of infections and diseases can cause an enlarged spleen. The enlargement might be temporary, depending on treatment. Contributing factors include:

• Viral infections, such as mononucleosis
• Bacterial infections, such as syphilis or an infection of your heart's inner lining (endocarditis)
• Parasitic infections, such as malaria
• Cirrhosis and other diseases affecting the liver
• Various types of hemolytic anemia — a condition characterized by early destruction of red blood cells
• Blood cancers, such as leukemia and myeloproliferative neoplasms, and lymphomas, such as Hodgkin's disease
• Metabolic disorders, such as Gaucher disease and Niemann-Pick disease
• Pressure on the veins in the spleen or liver or a blood clot in these veins
• Autoimmune conditions, such as lupus or sarcoidosis

How the spleen works

Your spleen is tucked below your rib cage next to your stomach on the left side of your belly. Its size generally relates to your height, weight and sex.

This soft, spongy organ performs several critical jobs, such as:

• Filtering out and destroying old, damaged blood cells
• Preventing infection by producing white blood cells (lymphocytes) and acting as a first line of defense against disease-causing organisms
• Storing red blood cells and platelets, which help your blood clot

An enlarged spleen affects each of these jobs. When it's enlarged, your spleen may not function as usual.