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Hairy Cell Leukemia

NORD is very grateful to Javier Munoz, MD, FACP, Hematology and Oncology, Banner MD Anderson Cancer Center, Gilbert, Arizona, for assistance in the preparation of this report.

Synonyms of Hairy Cell Leukemia

  • HCL
  • Leukemic Reticuloendotheliosis

Disorder Subdivisions

  • No subdivisions found.

General Discussion

General Discussion
Hairy cell leukemia (HCL) is a rare type of blood cancer characterized by abnormal changes in white blood cells known as B lymphocytes. The bone marrow creates too many of these defective cells, known as "hairy cells" because of the thin hair-like projections found on their surface. Overproduction and accumulation of hairy cells causes a deficiency of normal blood cells (pancytopenia), including an abnormal decrease of certain white blood cells (neutrophils [neutropenia]) and certain red blood cells (platelets [thrombocytopenia]). Affected individuals usually exhibit fatigue, weakness, fever, weight loss, and/or abdominal discomfort due to an abnormally enlarged spleen (splenomegaly). In addition, affected individuals may have a slightly enlarged liver (hepatomegaly) and may be unusually susceptible to bruising and/or severe infection. The exact cause of hairy cell leukemia is not known.


Onset of hairy cell leukemia is usually gradual. Symptoms are nonspecific and may include a general feeling of ill health (malaise), fatigue, weakness, fever, night sweats, and/or weight loss. In addition, affected individuals may experience abdominal pain and a feeling of abdominal fullness due to an abnormally enlarged spleen (splenomegaly).

In some cases, affected individuals may have a slightly enlarged liver (hepatomegaly) and may be unusually susceptible to bruising and/or severe, frequent infections. These infections were often the most serious complication of hairy cell leukemia, but occur rarely with advances in treatment.


The exact cause of hairy cell leukemia is unknown.

The specific symptoms of hairy cell leukemia are due to overproduction of abnormal "hairy" cells, which results in a deficiency of the three main types of blood cells - red and white blood cells and platelets. Red blood cells deliver oxygen to the body, white blood cells help fight infections, and platelets assist in clotting to stop blood loss.

Affected Populations

Hairy cell leukemia is a rare disorder that affects males four times more often than females (M4:F1). Hairy cell leukemia affects about 6,000 persons in the United States. Approximately 600-800 new cases are diagnosed each year. Most of the affected individuals are males 50 years of age or older. However, the disorder may occur in individuals between 20 to 80 years of age.

Hairy cell leukemia accounts for one to two percent of all cases of adult leukemia. It was first identified in 1958.

Related Disorders

Leukemia is a form of cancer affecting the bone marrow and blood. It is characterized by the uncontrolled accumulation of cancerous blood cells. Acute forms of leukemia often result in low levels of red and white blood cells and platelets (pancytopenia). (For more information, choose "leukemia" as your search term in the Rare Disease Database.)

Myelofibrosis is a condition characterized by formation of fibrous tissue (fibrosis) within the bone marrow. Bone marrow is sponge-like tissue found within the bones of the body and is responsible for the production of all blood cells (i.e., red and white blood cells and platelets). Myelofibrosis may occur as a secondary characteristic to other disorders such as polycythemia vera, certain metabolic disorders, and/or chronic myeloid leukemia. In many cases, the cause of myelofibrosis is unknown (idiopathic). In idiopathic myelofibrosis, the ability of the bone marrow to produce red blood cells may be impaired. Symptoms of idiopathic myelofibrosis may include abnormally low levels of circulating red blood cells (anemia), an abnormally large spleen (splenomegaly), an abnormally large liver (hepatomegaly), weight loss, weakness and fatigue due to replacement of normal bone marrow cells, and/or episodes of severe pain in the abdomen, bones, and joints. (For more information on this disorder, choose "myelofibrosis" as your search term in the Rare Disease Database.)

Standard Therapies

Until recently, treatment of hairy cell leukemia consisted of surgically removing the spleen (splenectomy). In rare cases, in which individuals do not respond to drug treatments, a splenectomy may still be performed. Chemotherapy drugs, specifically purine analogs such as cladribine and pentostatin, are now the initial treatment option for most individuals with hairy cell leukemia. Those who do not have any symptoms may not need treatment right away.

The drug cladribine (Leustatin©) has been approved by the Food and Drug Administration (FDA) for treatment of HCL. This drug interferes with the development of cancer cells and has proven to be an effective drug in the treatment of hairy cell leukemia. For more information, contact:

Ortho Biotech Products
430 Route 22 E.
Bridgewater, NJ 08807-0914
Phone: 908-541-4000

The orphan drug pentostatin (Nipent) has been approved by the FDA for affected individuals who do not respond to initial therapy for hairy cell leukemia. According to studies, the drug produced "durable complete responses" in individuals with hairy cell leukemia. The drug is manufactured by SuperGen, Inc. For more information, contact:

SuperGen, Inc.
Two Annabel Lane, Suite 220
San Ramon, CA 94583
Tel: (925) 327-0200
Fax: (925) 327-7347

Approximately 10 percent of individuals will not respond to treatment with chemotherapy drugs. In addition, some individuals cannot take such drugs. In such cases, individuals may be treated with biological therapies such as alpha interferon. Biologic therapies attempt to use the body's immune system directly or indirectly to treat the malignancy.

The orphan drug alpha interferon has been approved by the FDA for use in the treatment of hairy cell leukemia. The drug is manufactured by Hoffman-LaRoche and Schering Plough. Interferon is a hormone naturally produced by the body to fight viral infections. Treatment with alpha interferon may include daily injections for up to six months, followed by maintenance injections three times weekly. Side effects mimic flu-like symptoms, which diminish over time.

Investigational Therapies

A biological therapy known as rituximab (Rituxan©) has been used to treat individuals with hairy cell leukemia who do not respond to conventional therapy. Rituximab is an antibody that attaches itself to hairy cells. The drug has been approved for non-Hodgkin's lymphoma and is being studied to determine its long-term safety and effectiveness as a therapy for hairy cell leukemia.

Interleukin-2 has been used on an experimental basis to restore natural killer cell activity in hairy cell leukemia.

The drug deoxycoformycin is being used in clinical trials on patients with hairy cell leukemia. Information about obtaining this drug can be located through the Comprehensive Cancer Center (Dr. Eric Kraut), Ohio State University, Columbus, Ohio, or the Investigational Drug Branch of the National Cancer Institute in Bethesda, Maryland.
Most patients with hairy cell leukemia carry a BRAF gene mutation, and these gene mutations have also been identified in melanoma and other cancers. Vemurafenib, a drug that targets the effects of BRAF mutations, is FDA approved for the treatment of melanoma. Responses to vemurafenib have been described in patients with hairy cell leukemia, and clinical trials are evaluating BRAF inhibition in this condition.

Information on current clinical trials is posted on the Internet at All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010

For information about clinical trials sponsored by private sources, contact:
For information about clinical trials conducted in Europe, contact:

Hairy Cell Leukemia Resources



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Dietrich S, Glimm H, Andrulis M, von Kalle C, Ho AD, Zenz T. BRAF inhibition in refractory hairy-cell leukemia. N Engl J Med. 2012;366(21):2038-40.
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Flinn IW, Kopecky KJ, Foucar MK, et al. Long-term follow-up remission duration, mortality, and second malignancies in hairy cell leukemia patients treated with pentostatin. Blood. 2000;96:2981-86.

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Zinzani P, Magagnoli M, Bendandi M, et al. Long-term follow-up of hairy cell leukemia patients treated with 2-chlorodeoxyadenosine. Haematologica. 2000;85:922-25.

Johnston JB, Eisenhauer E, Wainman N, Corbett WE, Zaentz SD, Daeninck PJ. Long-term outcome following treatment of hairy cell leukemia with pentostatin (Nipent): a National Cancer Institute of Canada study. Semin Oncol. 2000;27:32-36.

Tetreault SA, Robbins BA, Saven A. Treatment of hairy cell leukemia-variant with cladribine. Leuk Lymphoma. 1999;35:347-54.

Piro LD, Carrera CJ, Carson DA, Beutler E. Lasting remissions in hairy-cell leukemia induced by a single infusion of 2- chlorodeoxyadenosine. N Engl J Med. 1990;322:1117-21.

van Norman AS, Nagorney DM, Martin JK, Phyliky RL, Ilstrup DM. Splenectomy for hairy cell leukemia; a clinical review of 64 patients. Cancer. 1986;57:644-48.

Thompson JA, Brady J, Kidd P, Fefer A. Recombinant alpha-2 interferon in the treatment of hairy cell leukemia. Cancer Treatment Rep. 1985;7-8:791-93.

Groopman JE. Therapeutic options in hairy cell leukemia. Semin Oncol. 1985;12:30-34.

Besa EC. Hairy Cell Leukemia. Medscape. Feb 14, 2012. Available at: Accessed: September 23, 2013.

Hairy Cell Leukemia. Mayo Foundation for Medical Education and Research. March 21, 2012. Available at Accessed: September 23, 2013.

The information in NORD’s Rare Disease Database is for educational purposes only. It should never be used for diagnostic or treatment purposes. If you have questions regarding a medical condition, always seek the advice of your physician or other qualified health professional. NORD’s reports provide a brief overview of rare diseases. For more specific information, we encourage you to contact your personal physician or the agencies listed as “Resources” on this report.

Report last updated: 2013/10/25 00:00:00 GMT+0

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