Chronic lymphocytic leukemia is a type of cancer that causes the bone marrow to produce too many lymphocytes, states the National Cancer Institute. Lymphocytes are cells used to help the immune system fight infection.
As of 2015, scientists do not know exactly what causes CLL, reports Mayo Clinic. Something causes a genetic mutation inside the blood-producing cells causing those cells to produce abnormal lymphocytes. Instead of dying like normal lymphocytes, the abnormal lymphocytes keep multiplying, which causes them to build up in the blood and some organs. CLL is more common in some groups of people than others. Men have a higher risk of developing the disease than women, and most people diagnosed with CLL have already passed the age of 60. Chemical exposure or a family history of blood or bone marrow cancer also increases the risk for developing CLL.
CLL may not cause any symptoms at first, states Mayo Clinic. As the disease progresses, a person with CLL experiences fatigue, night sweats, frequent infections and enlarged lymph nodes. CLL also causes fevers and pain on the upper left side of the abdomen. Blood tests, bone marrow aspiration and bone marrow biopsy are used to diagnose CLL. These test also help determine if CLL is in its early or advanced stages.