Hairy cell leukemia is a cancer of the white blood cells. The white blood cells help fight off germs. There are a few different types of white blood cells. The white blood cells involved in hairy cell leukemia are called B cells. B cells are also 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 undergone changes to become 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 is usually 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 called hairy cell leukemia variant. It's considered a separate type of cancer from hairy cell leukemia, even though it has a similar name.

Hairy cell leukemia might not cause symptoms. Sometimes a health care provider finds it by accident during a blood test for another condition.

When it causes symptoms, hairy cell leukemia might cause:

• A feeling of fullness in your belly that may make it uncomfortable to eat more than a little at a time
• Fatigue
• Easy bruising
• Recurring infections
• Weakness
• Losing weight without trying

When to see a doctor

Make an appointment with your health care provider if you have any persistent signs and symptoms 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 develop changes in their DNA. A cell's DNA contains 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 when healthy cells would 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. For example, the extra cells can cause swelling in the spleen, liver and lymph nodes. If there isn't enough room for healthy blood cells, this can lead to frequent infections, easy bruising and feeling very tired.

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. It's rare in children.
• Males. Hairy cell leukemia can happen to anyone. But it's more likely in males.

Hairy cell leukemia often gets worse very slowly. Sometimes it stays stable for many years. For this reason, few complications of the disease occur.

Too few healthy blood cells

If there are too many leukemia cells in the body, they 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 control bleeding. If the number of platelets in your blood is low, you might notice that you bruise more easily. You might also have bleeding from the nose or gums.
• Anemia. Your body needs healthy red blood cells to carry oxygen through your body. Having too few red blood cells is called anemia. Anemia can make you feel very 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's lymphoma, Hodgkin's lymphoma and others. It's not clear if the other cancers are caused by hairy cell leukemia or by cancer treatments.

Hairy cell leukemia treatments are good at controlling the disease. But they can't make it go away completely. Instead, treatments can control the cancer so that you can go about your life as usual. People with hairy cell leukemia can live with the disease 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 often gets worse very slowly over time. You might choose to wait and have treatment if the cancer starts to cause symptoms.

If you don't have treatment, you'll have regular appointments with your health care provider. You might have blood tests to see if hairy cell leukemia is getting worse.

You might decide to start treatment if you start to get hairy cell leukemia symptoms. Most people with hairy cell leukemia will eventually need treatment.

Chemotherapy

Chemotherapy is a drug treatment that uses powerful drugs to kill cancer cells. It's often the first treatment for hairy cell leukemia. Chemotherapy is very effective for hairy cell leukemia. Most people get a complete or partial remission after chemotherapy. Remission means you have no signs of cancer.

Chemotherapy for hairy cell leukemia can be given as a shot. Or it can be given as an infusion into a vein.

If your hairy cell leukemia comes back, your provider might recommend repeating chemotherapy with the same drug or trying a different drug. Another option may be targeted drug therapy.

Targeted drug therapy

Targeted drug treatments attack specific chemicals present within cancer cells. By blocking these chemicals, targeted drug treatments can cause cancer cells to die.

Targeted drug therapy is sometimes used as a first treatment for hairy cell leukemia. It can be used with chemotherapy. More often, targeted therapy is an option if the cancer comes back after chemotherapy.

Your health care provider will have your cancer cells tested to see whether targeted drug therapy is likely to work for you.

No alternative medicines are helpful for treating hairy cell leukemia. Alternative medicine might be helpful in other ways. It may help you cope with the stress of a cancer diagnosis and the treatment side effects.

Talk to your health care provider about your options, such as:

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

A cancer diagnosis can feel overwhelming. To help you cope, you might consider trying to:

• Find out enough to feel comfortable making decisions about your care. Learn about hairy cell leukemia and cancer treatments. This can help you feel more confident about making decisions about your treatment. Ask your health care provider to suggest some reliable sources of information to get you started.

• Connect with other cancer survivors. Friends and family provide an important support network during your cancer experience. But they can't always understand what it's like to face cancer. Other cancer survivors provide a unique network of support.

  Ask your provider about support groups or organizations in your community that can connect you with other cancer survivors. Organizations such as the Hairy Cell Leukemia Foundation and the Leukemia & Lymphoma Society offer ways to connect with others online.

• Take care of yourself. You can't control whether your hairy cell leukemia comes back, but you can control other aspects of your health.

  Take care of yourself by eating 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 your usual health care provider if you have any symptoms that worry you. If your provider suspects you may have hairy cell leukemia, they may suggest that you see a specialist. This might be a doctor who treats diseases of the blood and bone marrow. This doctor is called a hematologist.

Appointments can be brief, so it's a good idea to be prepared. Here's some information to help you get ready.

What you can do

• Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance. For example, you might need to restrict your diet.
• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medications, vitamins or supplements that you're taking.
• Consider taking a family member or friend along. Sometimes it can be hard to remember all the information provided during an appointment. Someone who comes with you may remember something that you missed or forgot.
• Write down questions to ask your doctor.

Your time with your provider is limited. Prepare a list of questions so that you can make the most of your time together. List your questions from most important to least important in case time runs out. For hairy cell leukemia, some basic questions to ask include the following:

• What kinds of tests do I need?
• Will I need treatment for my hairy cell leukemia?
• If I don't have treatment, will my leukemia worsen?
• If I need treatment, what are my options?
• Will treatment cure my hairy cell leukemia?
• What are the side effects of each treatment option?
• Is there one treatment you feel is best for me?
• How will cancer treatment affect my daily life?
• I have these other health conditions. How can I best manage them together?
• Are there any restrictions that I need to follow?
• Should I see a specialist? What will that cost, and will my insurance cover it?
• Are there brochures or other printed material that I can take with me? What websites do you suggest?

What to expect from your doctor

Your provider is likely to ask you a number of questions. Being ready to answer them may allow more time later to cover other points you want to address. Your provider may ask:

• When did you begin having symptoms?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, makes your symptoms worse?