Chronic lymphocytic leukemia (CLL) is a type of cancer that affects the blood and bone marrow. It primarily involves the overproduction of a specific type of white blood cell called lymphocytes, which are crucial for the immune system. In CLL, these lymphocytes do not function properly and accumulate, leading to various health issues. The exact cause of CLL is not fully understood, but certain risk factors, such as age and family history, may increase the likelihood of developing the disease. Symptoms can include fatigue, swollen lymph nodes, and frequent infections. Diagnosis typically involves blood tests and bone marrow examinations.