Hairy Cell Leukemia

Hairy cell leukemia is a rare form of leukemia. It happens when your bone marrow makes abnormal white blood cells. There isn’t a cure for hairy cell leukemia, but many people remain cancer-free for years after treatment.


What is hairy cell leukemia?

Hairy cell leukemia is a rare form of leukemia, or cancer of your blood cells. If you have hairy cell leukemia, your bone marrow makes abnormal white blood cells that multiply. It’s called hairy cell anemia because the abnormal cells appear hairy when viewed under a microscope. Hairy cell leukemia is a serious illness that healthcare providers can’t cure. It’s a slow-growing disease, so some people may have this condition for years without developing symptoms. Treatment often eliminates hairy cell leukemia (remission). Some people treated for hairy cell leukemia remain cancer-free for years.

Who is affected by hairy cell leukemia?

Hairy cell leukemia mostly affects people ages 40 to 70. It affects five times as many men, and people assigned male at birth (AMAB), than women, and people assigned female at birth (AFAB). Hairy cell leukemia is more common in people who are white than in other ethnic groups.

Is hairy cell leukemia a common condition?

No, it’s not common in the United States. Healthcare providers estimate between 800 and 1,000 people will be diagnosed with hairy cell leukemia every year. In comparison, the American Cancer Society estimated that in 2022, nearly 70,000 people in the United States would be diagnosed with some form of leukemia.

How does hairy cell anemia leukemia affect my body?

Hairy cell leukemia starts in your bone marrow, the spongy center of your bones that produces blood cells. These cells start as stem cells that eventually become red blood cells, white blood cells or platelets.

In hairy cell leukemia, stem cells that typically become healthy B-lymphocytes, or B-cells, become abnormal lymphocytes. B-cells are a type of white blood cell. Healthcare providers may use the term leukemia cell when talking about the abnormal blood cells that cause hairy cell leukemia. The abnormal cells build up in your blood and bone marrow, crowding out healthy white blood cells, red blood cells and platelets. When that happens, your bone marrow doesn’t make enough blood cells, setting the stage for several medical issues:

  • You may develop anemia because your bone marrow can’t produce the normal amount of red blood cells.
  • You may develop neutropenia because your bone marrow hasn’t developed enough white blood cells to fight off infections. Neutropenia happens when you don’t have enough neutrophils, the most common form of white blood cells.
  • You may bleed and bruise more easily because you don’t have the normal number of platelets that help blood clot. Healthcare providers may call this thrombocytopenia.
  • You may develop splenomegaly. This is when your spleen becomes enlarged, as leukemia cells gather in it.


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Symptoms and Causes

What are hairy cell leukemia symptoms?

What causes hairy cell leukemia?

Healthcare providers don’t know what causes hairy cell leukemia, but they’re looking closely at a certain genetic mutation that appears in 85% of people who have hairy cell leukemia. While a certain genetic mutation, or change, may cause hairy cell leukemia, the change isn’t one that’s inherited. Healthcare providers call this an acquired mutation, meaning the genes in question mutated during people’s lifetimes. Researchers don’t know how or why this acquired mutation happens.


Diagnosis and Tests

How do healthcare providers diagnose hairy cell leukemia?

  • Complete blood count (CBC) with differential: This test measures the number of red and white blood cells and platelets. The differential measures the different types of white blood cells.
  • Peripheral blood smear: In this test, healthcare providers look at blood cells under a microscope. This is the test where healthcare providers look for leukemia cells that have the tiny hair-like projections that give hairy cell leukemia its name.
  • Bone marrow aspiration and bone marrow biopsy: Healthcare providers do these tests to look for signs of leukemia in your bone marrow and to measure the number of blood cells in your bone marrow.
  • Computed tomography (CT) scan: CT scans make detailed pictures of areas inside of your body. Healthcare providers may do this test to examine the size of your spleen, liver and lymph nodes.
  • Flow cytometry: This test measures the number of cells in a sample, the percentage of live cells in a sample and certain characteristics of cells, such as size, shape, and the presence of tumor markers on the cell surface. Hairy cells have a surface protein pattern that’s different from healthy B-cells.

Management and Treatment

How do healthcare providers treat hairy cell leukemia?

If you have hairy cell leukemia but don’t have symptoms, your healthcare provider may recommend “watchful waiting.” This means they’ll carefully monitor your overall health and watch for early symptoms or signs of hairy cell leukemia.

If you have symptoms, most healthcare providers use chemotherapy to treat hairy cell leukemia. If hairy cell leukemia affects your spleen, they may recommend a splenectomy, which is surgery to remove your spleen.



How can I reduce my risk for developing hairy cell leukemia?

You may not be able to reduce your risk. Hairy cell leukemia risk factors are things you can’t change, like growing older, your sex, being white or having a particular biological family medical history. While a certain genetic mutation, or change, may cause hairy cell leukemia, the change isn’t one people inherit.

Outlook / Prognosis

Can you recover from hairy cell leukemia?

No, hairy cell leukemia is a chronic illness that healthcare providers can’t cure. But they can offer treatment that puts hairy cell leukemia into remission. (Remission means you don’t have signs or symptoms of hairy cell leukemia.) About 90% of people receiving chemotherapy for hairy cell leukemia are alive five years after starting treatment. Some studies indicate that most people with hairy cell leukemia may live nearly as long as people who don’t have this condition.

Does hairy cell leukemia come back?

Yes, hairy cell leukemia can come back (recur) months or years after you finish treatment. Healthcare providers may refer to this as “relapsing” or “recurrent hairy cell leukemia.” If that happens, they may use the chemotherapy they used previously to treat your condition, or they may recommend a different chemotherapy.

Living With

I have hairy cell leukemia. How do I take care of myself?

No type of cancer is easy to live with, but hairy cell leukemia poses unusual challenges. For example, you can have hairy cell leukemia without having symptoms. In that case, your healthcare provider may recommend delaying treatment until you do have symptoms. This is “watchful waiting.” On the other hand, people who have symptoms and are receiving treatment may be concerned about late effects. Late effects are conditions and medical issues that may happen long after you’ve finished treatment.

Watchful waiting

Watchful waiting may be stressful. While you don’t have to worry about treatment or side effects, you still may worry about not receiving treatment. You may feel anxious about waiting for symptoms to show up and then waiting for treatment.

It may help to know that your healthcare provider is carefully watching over you as you wait so they can move quickly to begin treatment. They’ll schedule regular appointments so they can evaluate your overall health and complete blood and other tests. In the meantime, there may be steps you can take to support your overall health. Ask your healthcare provider for recommendations.

Late effects

As the name implies, late effects are side effects that may surface months and years after someone finishes treatment for hairy cell leukemia. Your healthcare provider will discuss your treatment plan with you, including side effects that may happen during treatment or as late effects. It’s important to remember not everyone who has treatment for hairy cell leukemia will develop potential late effects. Talk to your healthcare provider if you’re worried about treatment late effects. They know your medical situation and your treatment, and will be able to provide some perspective on what you may expect.

I have hairy cell leukemia. When should I see my healthcare provider?

That depends on your situation. If you’re receiving treatment for hairy cell leukemia, you should contact your healthcare provider if your symptoms get worse or you’re having side effects that are more intense than you anticipated. If you’re watching and waiting, you should contact them as soon as you notice symptoms.

A note from Cleveland Clinic

Hairy cell leukemia is a rare leukemia that develops very slowly. Some people may have hairy cell leukemia for years before having any symptoms. Those who do have symptoms may receive treatment that puts hairy cell leukemia into remission, meaning you don’t have signs or symptoms of hairy cell leukemia. If you have hairy cell leukemia, your healthcare provider will explain how the condition will affect you and what you can expect.

Medically Reviewed

Last reviewed on 06/06/2022.

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