Hairy Cell Leukemia

Overview

Hairy cell leukemia is a rare and usually slow-growing cancer of the blood and bone marrow. It develops from a type of white blood cell called a B lymphocyte, which becomes abnormal and multiplies. Under a microscope, these cells have fine, hair-like projections, which gives the disease its name.

As the abnormal cells build up in the bone marrow and spleen, they crowd out normal blood cell production, leading to low blood counts. Although it is a cancer, hairy cell leukemia tends to progress slowly, and modern treatments are highly effective, with many people achieving long-lasting remission.

The spleen, an organ in the upper left abdomen that filters blood, often becomes enlarged in hairy cell leukemia as the abnormal cells collect there. This enlargement can cause discomfort and can also worsen low blood counts. Because the disease usually grows slowly, some people are diagnosed before they ever notice symptoms, simply through an unexpected finding on a routine blood test.

Symptoms

Some people have no symptoms and the condition is found on a routine blood test. When symptoms occur, they often come from low blood counts and an enlarged spleen:

• Fatigue and weakness from anemia
• Frequent or hard-to-clear infections from low white blood cells
• Easy bruising or bleeding from low platelets
• A feeling of fullness or discomfort in the left upper abdomen from an enlarged spleen
• Unexplained weight loss, fever, or night sweats

Causes

The exact cause is not fully understood, but the disease arises from genetic changes in a B lymphocyte:

• Acquired gene mutation: Most cases involve a specific mutation in a gene that drives the abnormal cells to grow. This change develops during life and is not inherited.

The reason these mutations occur is usually unknown. Hairy cell leukemia is not contagious and is not caused by anything a person did.

Risk Factors

• Older adult age
• Male sex, as it is more common in men
• The cause of most cases is unknown, and clear preventable risk factors have not been established

Diagnosis

Diagnosis is based on examining the blood and bone marrow:

• Blood counts and blood smear: Often show low blood counts and the characteristic hairy cells under the microscope.
• Bone marrow biopsy: Confirms the diagnosis and shows the extent of marrow involvement.
• Specialized cell tests: Flow cytometry and tests for the specific gene mutation identify the cells precisely.
• Imaging: May be used to assess spleen size.

Treatment

Treatment is highly effective and is often not needed right away if there are no symptoms:

• Watchful waiting: People without symptoms may simply be monitored at first.
• Chemotherapy: Specific medicines called purine analogs are the main treatment and produce long remissions in most people.
• Targeted and immune therapies: Antibody-based and targeted drugs are used in some cases, including when the disease returns.
• Supportive care: Treating infections and managing low blood counts.

Many people achieve long-lasting remission, and treatment can often be repeated successfully if the disease returns.

After treatment, people are monitored with periodic blood tests and check-ups to confirm that blood counts have recovered and to catch any return of the disease early. Because hairy cell leukemia can come back years later, this long-term follow-up is an important part of care. When it does recur, the same or similar treatments often work again, which is one reason the long-term outlook is generally favorable.

Prevention

There is no known way to prevent hairy cell leukemia because its cause is not well understood and the underlying gene change is acquired, not inherited. The most useful step is seeking medical evaluation for persistent fatigue, frequent infections, easy bruising, or abdominal fullness so that any blood disorder is identified and treated early.

When to See a Doctor

See a doctor for ongoing fatigue, repeated infections, easy bruising or bleeding, unexplained weight loss, or fullness in the upper left abdomen. Seek urgent care for a high fever with signs of serious infection, heavy or uncontrolled bleeding, or sudden severe abdominal pain, which may relate to the spleen and need prompt attention.

Related Topics

Frequently Asked Questions

References

1. National Cancer Institute (NCI). Hairy Cell Leukemia Treatment.
2. MedlinePlus, U.S. National Library of Medicine. Hairy cell leukemia.
3. American Cancer Society. Leukemia.
4. Leukemia & Lymphoma Society. Hairy Cell Leukemia.