Hairy Cell Leukemia

Hairy cell leukemia is a type of chronic lymphocytic leukemia (CLL). CLL is one of the four major categories of leukemia. Based on the category and subset, the physician can determine what treatment will work best for the patient. Hairy cell leukemia is a slow-growing malignant disorder that affects white blood cells called lymphocytes. The disease is called hairy cell leukemia because the leukemic lymphocytes have short, thin projections from their surface that look like hairs when examined under a microscope. The hairy cells accumulate in the bone marrow and spleen and to a lesser extent in lymph nodes. The accumulation of these functionless leukemic lymphocytes in the marrow prevents the production of normal blood cells by the marrow. These normal cells are of great importance to the well-being of the patient. Researchers do not understand the ways in which leukemic cells get their competitive advantage, overgrow the marrow and prevent normal cells from being made.

Causes and Risk Factors
The cause of hairy cell leukemia and the means to prevent it are unknown. There seems to be no direct link between the disease and exposure to environmental toxins. The disease has very occasionally occurred in members of the same family. However, no hereditary pattern has been established.

Symptoms and Signs
Hairy cell leukemia may be difficult to diagnose early because its symptoms are vague and resemble those of other illnesses. The disease may be discovered during a medical evaluation because of an enlarged spleen or an unexpected decrease in normal blood cell counts. Patients may experience a feeling of discomfort or fullness in the upper left side of their abdomen as a result of the enlarged spleen. Unexplained weight loss and loss of a sense of well-being may bring patients to their physician.

Hairy cells accumulate in the bone marrow preventing the marrow from producing sufficient normal blood cells. The disruption of normal blood cell production leads to anemia (deficiency of red cells), thrombocytopenia (deficiency of platelets) and increased risk of infection (deficiency of white cells called neutrophils and monocytes which fight infection). Often all three blood cell types are deficient (referred to as pancytopenia). Although the hairy cells are abnormal types of lymphocytes, enlargement of lymph nodes is uncommon. Hairy cells accumulate in the marrow and spleen (probably where these cells grow best), but less so in the lymph nodes.

A marked decrease in phagocytes (neutrophils and monocytes) results in an increased chance of developing an infection. Some patients are first aware of the disease because of fever, chills, and other signs of infection. Black and blue marks, as a result of the low concentration of blood platelets, may occur on the skin without injury or after a minor injury.

Approach to Diagnosis

Medical history and physical examination
Complete blood counts
Bone marrow examination
Immunophenotyping
An accurate diagnosis is made by an evaluation of the cells in the blood and marrow. A physician may suspect hairy cell leukemia after performing a preliminary examination of the blood. The normal blood cell counts are low and there may be hairy cells detected in the blood. Occasionally, the hairy cells are numerous in the blood, resulting in an increase in the white cell counts. A bone marrow sample is often needed to confirm the disease. Obtaining a marrow sample from the hipbone can be done in a physician's office.


Special testing, called immunophenotyping, is also performed on the blood and marrow cells. Certain proteins are located on the surface of cells. Each type of cell has its own characteristic pattern of these proteins. Like other cells, hairy cells have a pattern that helps in their identification. Examination of these surface proteins (antigens) with antibodies that combine with their specific antigens and light up using special detection equipment, helps the doctor confirm the type of leukemia that is present. This method also helps to subclassify cell types, which may, in turn, help to decide on the best treatment to apply in that type of leukemia or lymphoma. The antigen on a cell is referred to as cluster of differentiation or "CD" with an associated number. For example, CD11c, 22, and 256 may be present on leukemic hairy cells.

Other tests include a computed tomography (CT) scan which uses multiple images in the computer to create a two dimensional image of the body at several levels. This is a technique for imaging body tissues and organs. The resulting images are displayed as a cross-section of the body at any level from the head to the feet. A CT scan of the chest or abdomen permits detection of an enlarged lymph node, liver or spleen. A CT scan can be used to measure the size of these and other structures during and after treatment. Use of the CT scan for staging enables the physician to determine the extent of enlarged nodes and other organ involvement in the thorax or abdomen. CT scans are more sensitive than x-rays in finding tumors. These studies can be repeated after treatment to determine if the abdominal lymph node or spleen enlargement has decreased or returned to normal size.