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.
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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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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
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 may include:
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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Hairy cell leukemia complications include:
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:
Your healthcare provider may recommend active surveillance or anticancer drugs.
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:
You may have questions and concerns about delaying treatment. Don’t hesitate to ask your care team what you can expect during active surveillance.
Chemotherapy is the most common treatment. You may receive cladribine (Leustatin®) or pentostatin (Nipent®). Other treatments are:
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You may develop serious infections. Contact your healthcare provider if you have the following symptoms:
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.
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.
Hairy cell leukemia can weaken your immune system. Here are some ways you can support it and protect yourself from infection:
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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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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.
Last reviewed on 06/25/2025.
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