Hairy cell leukemia (HCL) is chronic leukemia. It is caused by an abnormal change in a B lymphocyte (a type of white blood cell). The disease is called hairy cell leukemia, because the leukemic lymphocytes have small, thin projections on the surface that look like hairs when viewed under a microscope.
HCL is more common in men than in women. The average age of diagnosis is 52 years. The cause of HCL is unknown. There is no direct link established between the disease and exposure to polluting or poisonous agents (toxins) in the environment.
Is Hairy Cell Leukemia Hereditary?
There have been just a few cases where a hairy cell leukemia hereditary component can be evidenced and these are of special interest since there are elements that support the role of inheritance in leukemias. In identical twins, there is a degree of agreement of 20% for leukemia, and the increased frequency of familial leukemia in children with leukemia has been described.
The symptoms of hairy cell leukemia are not specific and may resemble other diseases. Hairy cells accumulate in the bone marrow, liver, and spleen (probably where these cells grow or survive better) and there is very little involvement of the lymph nodes.
The two most important findings that establish a diagnosis of hairy cell leukemia are enlargement of the spleen and an unexpected decrease in normal blood cell count. During the course of the disease, the production of normal blood cells is interrupted by the accumulation of hairy cells in the bone marrow. Patients may have:
–Thrombocytopenia (decrease in the number of platelets).
–Neutropenia and monocytopenia (decrease in a number of neutrophils and monocytes, types of blood cells that fight infections).
The reduced number of the three types of blood cells is known as “pancytopenia”. Patients with anemia often feel tired, pale or feel short of breath derived from a low red blood cell count. With low levels of blood platelet concentration, the patient may have bruises on the skin from a minor injury or even without injury. Patients with low levels of white blood cells are at increased risk of infection. Some patients realize that they have hairy cell leukemia initially due to fever, chills or other signs of infection. Patients may also have discomfort or a feeling of fullness in the upper left part of the abdomen as a result of an enlarged spleen and inexplicable weight loss.
Diagnosis of Hairy Cell Leukemia
By analyzing the blood cells and bone marrow of a patient, a hematopathologist (a doctor who specializes in examining tissues and diagnosing diseases) can make an accurate diagnosis for hairy cell leukemia. Hairy cells are difficult to find in the blood, but can often be identified by a thorough search. Occasionally there are many hairy cells in the blood, causing the total white blood cell count increases. However, neutrophil and monocyte count (types of white blood cells) are still extremely low.
It is usually necessary to perform a bone marrow aspiration (extraction of a liquid sample of cells from the bone marrow by a needle) and biopsy (extraction of a very small amount of bone with bone marrow cells) to diagnose hairy cell leukemia.
Imaging studies are done with special machines that produce the types of images that show the inside of the body. The images can be used to measure the extent of the illness. An ultrasound can be used to confirm the precise size of the spleen. Further imaging studies may be performed to identify a decrease in the size of the spleen, liver and lymph nodes as a measure of the patient’s response to treatment.
Enlargement of the abdominal, thoracic or superficial lymph nodes (lymphadenopathy) is not a common problem at the time of initial hairy cell leukemia diagnosis. In fact, this medical problem is found in only 5 to 10 percent of patients. In patients who have a relapse and those who are in the advanced stages of the disease there is a relatively high frequency of lymphadenopathy and, therefore, it may be necessary to perform a computed tomography (CT scan) in the course of their treatment for the hairy cell leukemia.
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