Hairy cell leukemia is a cancer of the white blood cells. The white blood cells help fight germs. The white blood cells involved in hairy cell leukemia are called B cells. B cells also are called B lymphocytes.

In hairy cell leukemia, the body makes too many B cells. The cells don't look like healthy B cells. Instead, they've changed into leukemia cells. The leukemia cells look "hairy" under a microscope.

Hairy cell leukemia cells keep living when healthy cells would die as part of the natural cell life cycle. The leukemia cells build up in the body and cause symptoms.

Hairy cell leukemia often gets worse slowly. Treatment might not need to start right away. When it's needed, treatment most often is with chemotherapy.

Scientists found a type of cancer that looks like hairy cell leukemia, but it gets worse much faster. This other type of cancer is sometimes called hairy cell leukemia variant. It's thought to be a separate type of cancer from hairy cell leukemia, despite its name.

Hairy cell leukemia may not cause symptoms. Sometimes a healthcare professional finds it by chance from a blood test for another condition.

When it causes signs and symptoms, hairy cell leukemia may cause:

• Pain or a feeling of fullness below the ribs.
• Tiredness.
• Easy bruising.
• Repeat infections.
• Weakness.
• Weight loss without trying.

When to see a doctor

Make an appointment with a doctor or other healthcare professional if you have symptoms that don't go away and that worry you.

It's not clear what causes hairy cell leukemia.

Hairy cell leukemia begins in the white blood cells. The white blood cells help fight germs in the body. There are a few types of white blood cells. The white blood cells involved in hairy cell leukemia are called B cells.

Hairy cell leukemia happens when B cells get changes in their DNA. A cell's DNA holds the instructions that tell a cell what to do. The changes tell the B cells to make a lot more B cells that don't work right. These cells go on living after healthy cells die as part of the natural cell life cycle.

The B cells that don't work right crowd out healthy blood cells in the bone marrow and other organs. This leads to the symptoms and complications of hairy cell leukemia.

The risk of hairy cell leukemia may be higher in:

• Older adults. Hairy cell leukemia can happen at any age. But most people diagnosed with hairy cell leukemia are in their 50s or 60s.
• People assigned male at birth. Hairy cell leukemia can happen to anyone. But it's more likely in people assigned male at birth.

Too few healthy blood cells

Hairy cell leukemia can cause too many diseased cells that can crowd out the healthy blood cells. That can lead to:

• Infections. Your body needs healthy white blood cells to fight off germs. If your body can't make enough healthy white blood cells, you might get more infections.
• Bleeding. Your body needs healthy platelet cells to manage bleeding. If the number of platelets in your blood is low, you might bruise more easily. You also might have bleeding from the nose or gums.
• Anemia. Your body needs healthy red blood cells to carry oxygen through it. Having too few red blood cells is called anemia. Anemia can make you feel tired.

Increased risk of other cancers

Some studies found that people with hairy cell leukemia have an increased risk of other types of cancer. The other cancers include non-Hodgkin lymphoma, Hodgkin lymphoma and others. Not all studies agree on whether there is an increased risk of other cancers after having hairy cell leukemia. Talk about it with your healthcare team if you're worried about your risk.

To diagnose hairy cell leukemia, a healthcare professional might start with a physical exam and ask you about your symptoms. Other tests might include blood tests, a CT scan and a procedure to remove some bone marrow for testing.

Hairy cell leukemia treatments can control the disease and help you go about your life as usual. But treatments most often can't cure the cancer. Instead, treatments for hairy cell leukemia help control symptoms and prevent complications. People with hairy cell leukemia can live with the condition for many years.

Treatment might not need to start right away

Treatment for hairy cell leukemia doesn't always need to start right away. This cancer may get worse slowly over time. You might choose to wait to have treatment if the cancer starts to cause symptoms.

If you don't have treatment, you may have regular appointments with your healthcare professional. You might have blood tests to see if hairy cell leukemia is getting worse.

You might decide to have treatment if you start to get hairy cell leukemia symptoms. Most people with hairy cell leukemia need treatment after a time.

Chemotherapy

Chemotherapy treats cancer with strong medicines. It's often the first treatment for hairy cell leukemia. Most people get a complete or partial remission after chemotherapy for hairy cell leukemia. Remission means you have no signs of cancer.

You get chemotherapy for hairy cell leukemia as a shot. Or you get it through a vein, called an infusion.

If your hairy cell leukemia comes back or if some cancer remains after treatment, your healthcare professional might suggest that you repeat chemotherapy with the same medicines or try another medicine.

Targeted therapy

Targeted therapy for cancer is a treatment that uses medicines that attack specific chemicals in the cancer cells. By blocking these chemicals, targeted treatments can cause cancer cells to die.

Targeted therapy sometimes is a first treatment for hairy cell leukemia. You can get targeted therapy with chemotherapy. More often, targeted therapy is a treatment for cancer that comes back after chemotherapy.

Your healthcare professional has your cancer cells tested to see whether targeted therapy is likely to work for you.

No alternative medicines treat hairy cell leukemia. But alternative medicine might help in other ways. It may help you cope with the stress of a cancer diagnosis and the treatment side effects.

Talk to your healthcare professional about your choices, such as:

• Art therapy.
• Exercise.
• Meditation.
• Music therapy.
• Relaxation exercises.
• Spirituality.

A cancer diagnosis can overwhelm you. Here are some ideas that might help you cope.

Learn enough to make decisions about your care

Find out more about hairy cell leukemia and cancer treatments. This can help you feel better about making choices about your treatment. Ask your healthcare professional to suggest good sources of information to get you started.

Find a good listener

Finding someone who is willing to listen to you talk about your hopes and fears can be helpful as you manage a cancer diagnosis. This could be a friend or family member. A counselor, medical social worker or clergy member also may offer helpful guidance and care.

Ask your healthcare team about support groups in your area or contact Blood Cancer United or the Hairy Cell Leukemia Foundation. Find support online through Mayo Clinic Connect, which is a community where you can connect with others for support, practical information and answers to everyday questions.

Take care of yourself

You can't control hairy cell leukemia, but you can manage other aspects of your health.

Eat a balanced diet with plenty of fruits and vegetables. Exercise regularly. Get enough sleep so that you wake up feeling refreshed. Find healthy ways to cope with the stresses in your life.

Start by seeing a healthcare professional if you have symptoms that worry you. For hairy cell leukemia, your healthcare professional might send you to a doctor who specializes in conditions of the blood and bone marrow. This doctor is called a hematologist.

Here's some information to help you get ready for your appointment.

What you can do

When you make the appointment, ask if there's anything you need to do before the appointment. For instance, you might need to change your diet. If you can, take a family member or friend to the appointment to help you remember the information your healthcare team gives you.

Make a list of:

• Your symptoms and when they began. Include any that don't seem linked to the reason for your appointment.
• Key personal information, including major stresses or recent life changes.
• All medicines, vitamins and supplements you take, including dosages.
• Questions to ask your healthcare professional.

For hairy cell leukemia, some basic questions might be:

• What tests do I need?
• Will I need treatment for my hairy cell leukemia?
• Without treatment, will my leukemia get worse?
• What treatments are there?
• How will cancer treatment affect my life?
• I have other health conditions. How can I manage them together?
• Are there brochures or other printed information that I can have? What websites do you suggest?

What to expect from your doctor

Your healthcare professional is likely to ask you questions, such as:

• Do your symptoms stay with you or come and go?
• How bad are your symptoms?
• What, if anything, makes your symptoms better?
• What, if anything, makes your symptoms worse?