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Hairy Cell Leukemia

Hairy cell leukemia is a rare leukemia. It happens when abnormal B lymphocytes multiply and build up in your bone marrow, lymph nodes, liver and spleen. It’s a slow-growing disease that doesn’t cause symptoms right away. Common symptoms are fatigue and frequent infections.

What Is Hairy Cell Leukemia?

Hairy cell leukemia is a rare blood cancer. It happens when your bone marrow makes too many abnormal B-cells — a type of white blood cell. These cells build up in your bone marrow, lymph nodes, liver and spleen.

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The name comes from how the cells appear under a microscope. They have tiny, hair-like projections. Hairy cell leukemia grows slowly and may not cause symptoms for many years.

Symptoms and Causes

Symptoms of hairy cell leukemia

Symptoms may include:

  • Fatigue: Low levels of red blood cells can make you feel tired all the time.
  • Fever and frequent infections: Low white blood cell levels may lead to serious infections that cause fevers.
  • Pain in your lower left side: Abnormal cells in your spleen can make it swell and cause pain on your left side. Your spleen may press on your belly. That can make you feel full even when you don’t eat a lot. You may lose weight without trying.
  • Pain in your lower right side: The cells may build up in your liver, so it swells and causes pain.
  • Shortness of breath: This is another anemia symptom from low red blood cell levels.
  • Swollen lymph nodes: Abnormal cells in your lymph nodes cause lumps in your neck, underarms and stomach.
  • Bruising or bleeding easily: Hairy cell leukemia keeps your bone marrow from making enough platelets. Platelets slow or stop bleeding under your skin (bruises) or when you have a nosebleed or cut.

Hairy cell leukemia causes

Experts don’t know the exact cause. Research shows that 90% of people with this disease have a change that affects the BRAF gene, which helps control cell growth. This change happens after you’re born. Researchers aren’t sure what triggers the change. But they believe the following things may increase your risk:

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  • Your age: This disease often affects people ages 40 to 70. On average, most of the people with hairy cell leukemia are 58 when they receive a diagnosis.
  • Your sex: It affects males more than females.
  • Exposure to Agent Orange: Researchers think this chemical may cause hairy cell leukemia and other types of leukemia.

Complications of this condition

Hairy cell leukemia complications include:

  • Infections: The disease makes it hard for your body to fight off infections.
  • Second cancer: You may develop a new cancer years after successful treatment.

Diagnosis and Tests

How doctors diagnose this condition

Healthcare providers will ask when your symptoms started. They’ll ask about your medical history. They may ask if you have frequent infections. They’ll also do a physical exam. Your provider may feel your lymph nodes, spleen and liver for signs of swelling. They might also refer you to a hematologist or a medical oncologist for more tests, including:

  • CBC with differential: Measures your red and white blood cells and platelets, and identifies different types of white blood cells
  • Peripheral blood smear: Looks for abnormal blood cells under a microscope
  • Bone marrow biopsy: Checks for abnormal cells in your bone marrow
  • CT scan or abdominal ultrasound: Evaluates the size of your spleen, liver and lymph nodes
  • Flow cytometry: Identifies physical or chemical changes in your cells

Management and Treatment

How is hairy cell leukemia treated?

Your healthcare provider may recommend active surveillance or anticancer drugs.

Active surveillance

In active surveillance, you don’t receive treatment until you have symptoms. But you’re not on your own during this time. You’ll see your cancer care team every three to six months. During those checkups, they’ll:

  • Ask about your overall health, particularly if you’re feeling more tired than usual
  • Do a physical exam and check your liver and spleen for signs of swelling
  • Do blood tests to check your blood cell and platelet levels

You may have questions and concerns about delaying treatment. Don’t hesitate to ask your care team what you can expect during active surveillance.

Anticancer drugs

Chemotherapy is the most common treatment. You may receive cladribine (Leustatin®) or pentostatin (Nipent®). Other treatments are:

  • Immunotherapy: Rituximab (Rituxan®) is a monoclonal antibody treatment. You may receive this along with chemotherapy as initial treatment. It’s also treatment if the disease comes back. Another type of immunotherapy is recombinant Interferon Alfa-2b (Intron A®).
  • Targeted therapy: Your provider may use antibody drug conjugates like rituximab.
  • Splenectomy: You may have this surgery if anticancer drugs aren’t effective, and abnormal cells make your spleen swell.

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When should I see my healthcare provider?

You may develop serious infections. Contact your healthcare provider if you have the following symptoms:

  • A fever above 100.4 degrees Fahrenheit (38 degrees Celsius) that doesn’t go away
  • A sore throat that lasts longer than a few days or gets worse
  • Belly pain that doesn’t go away or gets worse

Outlook / Prognosis

Is there a cure for hairy cell leukemia?

There’s no cure, but treatment often puts the disease into remission — sometimes for years at a time. It can come back, so ongoing medical care and support are important for this disease. Even so, hairy cell leukemia may not affect your life expectancy. One analysis concluded that people treated for the disease live as long as people who don’t have it.

What’s the survival rate for hairy cell leukemia?

The Leukemia and Lymphoma Society reports that 90% of people treated with the chemotherapy drug cladribine were alive five years after treatment. Your situation depends on factors like your age and general health. Other factors are your symptoms and how well your body reacts to treatment. Survival rates are estimates. Your care team will explain how survival rate data applies to you.

Is there anything I can do to feel better?

Hairy cell leukemia can weaken your immune system. Here are some ways you can support it and protect yourself from infection:

  • Eat well: Fruits, veggies, lean sources of protein and whole grains are just some examples of foods that support your immune system.
  • Build activity into your daily routine: Daily activity helps many aspects of your health, including your immune system.
  • Catch enough ZZZs: Not getting enough sleep can prevent your immune system from working as it should.
  • Stay up to date on vaccines: Vaccines train your body to fight off germs that can make you sick. Your provider will recommend when you should receive vaccines.

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A note from Cleveland Clinic

There’s no cure for hairy cell leukemia. That may be hard news to hear. So, it may help to know there are treatments that lead to long-term remission. You can’t control how long hairy cell leukemia will stay in remission. But you can take charge of your health. Steps like eating well and being active can protect your immune system from serious infections that hairy cell leukemia can cause.

Don’t hesitate to ask your team for help. They know you’re in this for the long run. They’ll be with you every step of the way.

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Care at Cleveland Clinic

A leukemia diagnosis can come as quite a shock. Cleveland Clinic’s blood cancer experts are here to guide you through it and help you move forward.

Medically Reviewed

Last reviewed on 06/25/2025.

Learn more about the Health Library and our editorial process.

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