eMedicine Specialties > Hematology > Stem Cells and Disorders

Hairy Cell Leukemia

Author: Emmanuel C Besa, MD, Professor, Department of Medicine, Division of Hematologic Malignancies, Kimmel Cancer Center, Thomas Jefferson University
Coauthor(s): Ulrich Woermann, MD, Consulting Staff, Division of Instructional Media, Institute for Medical Education, University of Bern, Switzerland
Contributor Information and Disclosures

Updated: Nov 24, 2008

Introduction

Background

Hairy cell leukemia (HCL) is a chronic lymphoid leukemia that was originally described in 1958 by Bouroncle and colleagues.^1,2 Hairy cell leukemia is a B-cell disease, and the abnormal cell has hairlike cytoplasmic projections on its surface.

Hairy cell leukemia is recognized as a clonal B-cell malignancy as identified by immunoglobulin gene rearrangements that result in a phenotype B-cell expression of surface antigens, which reflect the differentiation between the immature B-cell of chronic lymphocytic leukemia and the plasma cell of multiple myeloma.

For excellent patient education resources, visit eMedicine's Blood and Lymphatic System Center. Also, see eMedicine's patient education article Leukemia.

Pathophysiology

The abnormal cell in hairy cell leukemia is a clonal B-cell lymphocyte (see Image 1). This cell infiltrates the patient's reticuloendothelial system and interferes with bone marrow function, resulting in bone marrow failure or pancytopenia. The hairy cell also infiltrates the liver and spleen, resulting in organomegaly.

The etiology of hairy cell leukemia has not been determined, although some investigators suggest that exposures to benzene, organophosphorus insecticides, or other solvents may be related to disease development. This hypothesis has not been confirmed by other reports, although a French study that evaluated occupational exposure to pesticides and lymphoid neoplasms among men appears to support the hypothesis that occupational pesticide exposures may not only be involved in hairy cell leukemia, Hodgkin lymphoma, and multiple myeloma, but also may play a role in non-Hodgkin lymphoma.³ Further research is needed.

Exposure to radiation, agricultural chemicals, and wood dust, and a previous history of infectious mononucleosis have been suggested as etiologic associations in previous reports.

Overexpression of cyclin D1 protein, an important cell-cycle regulator, has been observed in hairy cell leukemia and may play a role in the molecular pathogenesis of the disease.

Accumulation of hairy cells in the bone marrow, liver, and spleen, with very little lymph node involvement, is characteristic of hairy cell leukemia. This pattern probably results from the expression of the integrin receptor alpha4-beta1 by the hairy cells and the interaction of the receptor with the vascular adhesion molecule-1 (VCAM-1) found in splenic and hepatic endothelia, bone marrow, and splenic stroma.

Frequency

United States

Hairy cell leukemia is relatively uncommon and accounts for 2% of all leukemia cases, which is about 600-800 new patients diagnosed each year.²

International

Some geographic variations have been observed with hairy cell leukemia, such as an extremely low incidence in Japan.

Mortality/Morbidity

• Symptoms of pancytopenia in hairy cell leukemia are related to anemia (fatigue and weakness), thrombocytopenia (bleeding or easy bruising), and neutropenia (infections).
• Abdominal discomfort is a common symptom, resulting from hepatosplenomegaly. It is usually controlled with new effective drug therapy, although late recurrences may occur. Recurrences are usually responsive to medications.

Race

• This disease is observed more commonly in whites. It has been reported to occur in Ashkenazi Jewish males, and it is rare in Japan and in those of African descent.²

Sex

• Hairy cell leukemia is observed mostly in males, with a male-to-female ratio of 4:1 to 5:1.²

Age

• Hairy cell leukemia occurs predominantly in middle-aged men, with a median age of 52 years.²

Clinical

History

• The most common symptoms and presenting complaints in hairy cell leukemia are weakness and fatigue due to anemia. Approximately one third of patients have bleeding from thrombocytopenia, and another one third have fever and infections from neutropenia.
• Symptoms related to organ infiltration of the reticuloendothelial system may occur. Abdominal discomfort from an enlarged spleen is present in one quarter of patients.
• Some patients may present with weight loss, fever, and night sweats, similar to other lymphoproliferative disorders.
• Hairy cell leukemia is associated with gram-positive and gram-negative bacterial infections, as well as atypical mycobacterial and invasive fungal infections. Other opportunistic infections, such as Legionella, toxoplasmosis, and listeriosis, have been reported.
• Hairy cell leukemia is associated with other systemic immunologic disorders including scleroderma, polymyositis, polyarteritis nodosa, erythematous maculopapules, and pyoderma gangrenosum.
• Other uncommon conditions may be associated with hairy cell leukemia, such as acquired factor VIII antibodies, paraproteinemia, and systemic mast cell disease.

Physical

• Splenomegaly is the most common physical finding in virtually every patient with hairy cell leukemia, and it is massive in more than 80% of patients.
• Hepatomegaly with mild liver function abnormalities is found in 20% of cases, and lymphadenopathy is found in 10%.
• A low-grade fever is part of the disease, but it may be due to an infection from the resulting neutropenia. In more than half of the cases, it is from a gram-negative organism. Atypical mycobacterial infections are common. Disseminated fungal infections and Pneumocystis carinii may occur in some cases of hairy cell leukemia.
• Peripheral lymphadenopathy is uncommon, with fewer than 10% of patients presenting with peripheral nodes larger than 2 cm in diameter. However, internal adenopathy may develop after a prolonged disease course and was found in 75% of patients at autopsy.

Causes

Hairy cell leukemia is due to proliferation of a clonal malignant B cell that infiltrates the reticuloendothelial cells, particularly the bone marrow, resulting in bone marrow failure.

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