Chronic lymphocytic leukemia (CLL)
is a cancer of the lymphocytes (a type of white blood cell) that begins in the stem cells of the bone marrow and then invades the blood. Overtime, CLL may also spread to the lymph nodes and other organs including the liver, spleen and lungs. It occurs when the stem cells that make lymphocytes become out of control and produce increasing amounts of abnormal lymphocytes (also called leukemic cells). Eventually, these abnormal cells replace normal lymphocytes and can crowd out other types of normal blood cells, leading to the features of the condition. Early signs and symptoms of CLL may include fatigue, weight loss, loss of appetite, fever, night sweats and/or frequent infections. The exact underlying cause of CLL is unknown; however, approximately 5% of affected people have other family members with the condition, which suggests there may be a genetic component in rare cases. The best treatment depends on many factors including the stage of the condition, the age of the affected person, the blood cell counts, whether the CLL has recurred, and the signs and symptoms present in each person. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.