Chronic Lymphocytic Leukemia

Understanding Chronic Lymphocytic Leukemia (CLL)
Chronic lymphocytic leukemia (CLL) is a type of cancer that affects the blood and bone marrow, the spongy tissue inside bones where blood cells are made. It involves a group of white blood cells called lymphocytes, which normally help the body fight infectionmayoclinic.org. CLL usually progresses more slowly than other types of leukemia and is considered a chronic leukemia. It is the most common type of leukemia in adultsmdanderson.org. In CLL, abnormal lymphocytes build up in the blood, bone marrow, lymph nodes, liver, and spleen, crowding out healthy blood cells.

Common signs and symptoms of CLL

General symptoms (many people are asymptomatic early on)

CLL is often found during routine blood tests before symptoms appear. When symptoms do develop, they can include:

• Fatigue or weakness
• Unexplained weight loss
• Fever without an obvious cause
• Night sweats
• Swollen lymph nodes, often painless, in the neck, armpits, or groin
• Frequent infections
• Pain or fullness in the upper left abdomen due to an enlarged spleen

Blood‑related complications

As abnormal lymphocytes replace normal cells in the bone marrow, people with CLL may develop:

• Anemia (low red blood cells), causing tiredness and shortness of breath
• Low platelets, leading to easy bruising or bleeding
• Increased risk of infections, due to impaired immune function

Causes and risk factors

The exact cause of CLL is unknown. It arises when DNA changes in blood‑forming cells lead to uncontrolled growth of abnormal lymphocytes. Factors associated with a higher risk include:

• Older age (most often in adults older than 55)
• Family history of CLL or other blood and bone marrow cancers
• Exposure to certain chemicals, including herbicides and insecticides such as Agent Orange used during the Vietnam War

Diagnosis

CLL is often detected when blood tests done for other reasons show an increased number of lymphocytes. If CLL is suspected, evaluation may include:

• Blood tests, including complete blood count and specialized testing of lymphocyte markers
• Bone marrow aspiration and biopsy, in some cases
• Additional tests to determine how advanced the leukemia is (staging) and whether specific genetic changes are present.

Treatment overview

Because CLL often grows slowly, not everyone needs treatment right away. A common approach for early, asymptomatic disease is “watchful waiting” (also called active surveillance), where the healthcare team regularly monitors blood counts and symptoms before starting therapy. When treatment is needed, options can include:

• Targeted therapies
• Chemotherapy
• Immunotherapy
• Stem cell (bone marrow) transplant, in select cases

The choice and timing of treatment depend on factors such as disease stage, how fast the leukemia is progressing, genetic features of the CLL cells, age, and overall health.