Chronic lymphocytic leukemia (CLL) does not typically cause symptoms in its early stages. As it progresses, it can lead to fatigue, lymph node swelling, weakness, frequent infection, and more.

CLL is a type of blood cancer that begins in your bone marrow. It affects white blood cells called lymphocytes. These white blood cells are part of your immune system and help your body fight infection.

CLL is the most common type of leukemia in adults. This kind of leukemia is considered chronic (long lasting) because it usually develops slowly over time.

Most people with CLL don’t have any signs or symptoms for years. In some cases, though, the disease can be aggressive and may grow faster.

Many people with CLL don’t have any symptoms at the time of diagnosis.

This type of leukemia may be found when a doctor orders blood tests for a routine checkup or an unrelated health condition. If a high number of lymphocytes show up on a blood test, it might lead your doctor to suspect leukemia.

For the small number of people who do experience symptoms early in the course of CLL, the symptoms may be subtle or confused for another more common health condition.

These symptoms include:

Another early symptom of CLL that may be noticed before other symptoms is a painless swelling of the lymph nodes. Common areas of swollen lymph nodes are the underarms and groin.

Some people may also experience pain or fullness in the stomach. This happens when CLL causes spleen enlargement.

When to schedule a medical appointment

Make an appointment to see a doctor if you notice any changes, such as lumps or swelling on the skin, or other persistent symptoms.

The doctor will ask how long and how often you’ve been experiencing the symptoms. Let your doctor know if you’ve had any recent infections, fever, or unexplained weight loss.

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Later stage or faster developing CLL may cause more serious or noticeable signs and symptoms in some people.

These include:

  • Frequent infections: Later stage CLL may cause chronic upper and lower respiratory tract infections. You may also get skin infections. Infections of the lungs, kidneys, and other organs can also develop.
  • Severe anemia: More serious kinds of anemia, such as autoimmune hemolytic anemia, can happen in 7–10% of people with CLL. This occurs when leukemia forms atypical antibodies that attack red blood cells (RBCs), leading to low levels of oxygen-carrying RBCs in the body.
  • Severe or chronic fatigue: Because CLL can cause anemia (a shortage of red blood cells) and low oxygen levels, it leads to ongoing or severe fatigue.
  • Easy or atypical bruising or bleeding: CLL can cause a condition called thrombocytopenia (reduced blood platelets) in rare cases. Lower levels of platelets affect how well your blood clots. This can cause more or atypical bleeding and bruising, such as bleeding gums or nosebleeds.
  • Headache and other neurological symptoms: CLL can affect the central nervous system in rare and more advanced cases. This can cause brain and nervous symptoms, like:
  • Other cancers: Some people with later stage CLL have a higher risk of developing other kinds of cancers. These include skin cancer, lung cancer, and cancers of the digestive tract. A very small number of people with CLL may develop a more aggressive form of cancer called diffuse large B cell lymphoma, or Richter’s syndrome.

The exact cause of CLL is not known. Experts do know that gene changes may happen in the cells that make blood cells. This mutation triggers the creation of atypical lymphocytes (white blood cells), which aren’t effective at fighting infection.

The atypical lymphocytes multiply and build up in the blood and other organs, like the liver and spleen, where they cause complications.

Some factors may raise your risk of developing CLL:

  • Family history: If your first-degree relative (parent, sibling, or child) has had CLL, you have a 5–7 times greater chance of developing it as well, according to the National Organization for Rare Disorders (NORD).
  • Age: CLL is most common in older adults, and risk increases with age. CLL rarely affects children and is rare under age 30 years The average age at diagnosis is around 72 years, per NORD.
  • Sex: Males are twice as likely to develop CLL than females, according to NORD.
  • Ethnicity: White Americans are significantly more likely to develop CLL than people of other races and ethnicities.
  • Toxin exposure: Some toxic environmental chemicals may raise the risk of CLL in some people. The U.S. Department of Veterans Affairs lists CLL as a disease linked to exposure to Agent Orange, a chemical used during the Vietnam War.

CLL is a cancer that affects white blood cells called lymphocytes. It happens most often in older adults.

Many people might not realize they have CLL because they might not have any symptoms in the early stages, or the symptoms are very mild.

In others, CLL may advance faster and cause more severe symptoms, as well as other complications.

Early stage CLL may take years to progress or happen sooner for some people. Let your doctor know if you experience any symptoms that are unusual for you or that last longer than usual.