Hairy cell leukemia (HLC) is a rare, chronic form of B-lymphocytic leukemia.
Patients usually present on diagnosis with pancytopenia, splenomegaly, and circulating hairy cells . All the signs and symptoms of hairy cell leukemia are the result of the proliferation of the abnormal white blood cells. All of the symptoms are reversible by reducing the number of malignant cells .
Signs and symptoms include the following  :
The cause of hairy cell leukemia is not known, however exposure to toxic chemicals, radiation, and wood dust have been implicated. The mechanism involved in the development of the abnormal hairy leukocytes is as yet unknown.
Patients may be asymptomatic and the disease is only identified when a complete blood count is done for an unrelated complaint . Most symptomatic patients present with complaints of fatigue, bruising, and abdominal pain. Other patients are seen initially for infections due to cytopenia .
Hairy cell leukemia is suspected initially when the abnormal hairy cells are present in the peripheral blood. Diagnosis is confirmed by demonstration of hairy cells in biopsy specimens from the bone marrow or spleen or in peripheral blood . Bone marrow aspiration and the presence of the abnormal cells is the least invasive means of making a definitive diagnosis . However, bone marrow aspiration is often impossible because of fibrosis of the marrow. Bone marrow biopsy is then the method of choice and the final step in confirming the diagnosis .
Diagnostic tests include :
The most consistent laboratory finding is cytopenia, usually affecting all three types of blood cells: red cells, white cells, and platelets . Physical examination may show significant signs of anemia, pale skin and mucosa, elevated pulse and respiratory rate, fatigue and exercise intolerance. In most cases splenomegaly is a presenting sign.
The goal of therapy in hairy cell leukemia is to decrease the risk of infection and other serious complications . Hairy cell leukemia is diagnosed based on the presence of the characteristic malignant white blood cells called hairy cells in the bone marrow. It is important to exclude other leukemia which present the same but require different treatment.
Once the diagnosis has been made the first determination to be made is if treatment is required at the time. Since all treatment modalities are associated with some side effects deferring treatment until the patient is symptomatic seems appropriate  . If the patient has significant cytopenia and its related problems: anemia, infections or bleeding, and/or significant splenomegaly, treatment should be started immediately .
Currently the initial treatment of choice are Purine analogues (nucleosides) and/or Interferon A. Both are effective treatment regimes, but nucleosides are the first line of treatment because they have a higher complete remission rate  . However, there are still instances where Interferon therapy is indicated   .
Splenectomy was the recommended treatment for hairy cell leukemia until the mid-1980s. The efficacy of splenectomy on survival of patients has not been demonstrated . In the past three decades, three very effective therapies have been approved for use with this disease: Interferon Alfa, pentostatin, and cladribine . Splenectomy is rarely performed currently except in cases of profound splenomegaly or excessive blood burden   .
Pentostatin and cladribine are the two most commonly used Purine analogues    . Studies have shown that a single courses of cladribine orpentostatin administered to patients with hairy cell leukemia have high response rates with a majority of patients achieving complete responses. Most patients then go on to long-lasting complete remissions. These rates have been recorded as high as 90-95%. Patients, approximately 30%, who relapse, may be re-treated successfully with repeat treatment    .
Alpha-interferon has a complete remission rate of 86 % . Interferon Alfa alone or in conjunction with one of the Purine analogues is indicated in patients with infections at diagnosis. Studies indicate that its inclusion in the treatment regime may increase the survival rate patients with advanced diesease. How this works is unclear .
Growth factors such as Granulocyte colony-stimulating factor (G-CSF) may be used in hairy cell leukemia to treat severe neutropenia. It can be given before, during and/or after treatment with a Purine analogue. Its routine use is not recommended .
Long-term follow-up with repeat bone marrow biopsy is necessary in order to detect relapse or residual disease early . Relapse has been reported in about 30% of patients. These cases respond well to retreatment with the drugs used in initial therapy (92%) .
Follow-up studies have shown a complete remission rate of approximately 95% and a partial response rate of 5%. These rates were often achieved after a single course of treatment . About 37% of treated patients experienced relapse after their first course of treatment. The time to relapse had a median of 42 months .
There is no clear guidelines to predict the progress of the disease. Since hairy cell leukemia primarily affects bone marrow and spleen and progresses slowly, prognosis depends on status of both these organs .
The response to purine analogue therapy is also a predictor of patient outcome. Those achieving complete remission did better than those with only partial response. For this reasons, the goal of treatment is achieve a complete remission .
The complications of hairy cell leukemia are primarily responsible for the morbidity and mortality associated with the disease. These complications include:
Complications associated with hairy cell leukemia are due to interruption in the production of normal blood cells. Anemia occurs with low red cell production. Decreased white cell production increases the risk of infection. Low platelet counts result in bleeding or excessive bruising. Abdominal pain and potential splenic rupture are complications resulting from splenomegaly which is present in almost all cases. Hepatomegaly and liver dysfunction may be found in 20% of patients  .
Approximately 30% of patients diagnosed with hairy cell leukemia develop secondary cancers during or following treatment for the disease .
All leukemias result from the proliferation immature of blood cell that are not functional. They do not then allow adequate production of normal erythrocytes, lymphocytes, granulocytes, and platelets. This pancytopenia results in severe anemia, life-threatening infection, bleeding, and the possibility of secondary malignancies . Hairy cell leukemia was first described by Bouroncle, et al. in 1958 . Hairy cell leukemia differs from other in two aspects: the presence of the distinctive hairy cells and the fact that it is the most treatable of all the blood malignancies .
The progression varies from patient to patient. Some patients may need no treatment; the majority (> 90 %) have complete remissions; some have chronic symptoms for many years; while still others die early from complications .
The annual incidence has been estimated to be approximately 1 in 500,000. It is a rare disorder accounting for only 2% of all leukemia cases. It affects men five times more often than women (5:1 incidence) and occurs most commonly in middle-age or older adults (average age of onset is 50 years) .
Hairy cell leukemia is seen more often in Caucasians and Ashkenazi Jewish males. It is rare in those of Japanese and African descent .
Hairy cell leukemia occurs most often in males, with a male-female ratio of 5 to 1 .
Hairy cell leukemia occurs most often in middle-aged men, with a median age of 52 years .
HCL is a rare, highly treatable, chronic B-cell leukemia. They disorder is distinguished by the presences of malignant white blood cells called hairy cells because of their characteristic appearance. These cells also possess a rare acid phosphatase enzyme (tartrate-resistant acid phosphatase (TRAP)) which acts as a useful marker for the disease  .
The abnormal cells proliferative slowly, so that symptomatology results from an abnormally prolonged cell survival rate . The effect of the accumulation of hairy cells on the other blood cell types is pancytopenia. The etiology of this is unclear .
The distinctive biological features include :
In hairy cell leukemia all types of blood cells are affected resulting in:
Unlike other lymphoid disorders, hairy cell leukemia has distinctive tissue distribution :
Hairy cell leukemia also has a distinctive pattern of bone marrow fibrosis.
Since the cause of hairy cell leukemia is not known, ways to prevent the disease are not clear. Some toxic chemicals and radiation have been implicated in the incidence of the disorder. Avoidance of these environmental substances may prevent the disease.
Hairy cell leukemia (HLC) is a chronic form of B-lymphocytic leukemia in which the predominant feature is the presence of characteristic malignant white blood cells  . These cells are named hairy cells because of protrusions on the surface of the cells that appear hair like . These malignant cells infiltrate the bone marrow, spleen, peripheral blood, and, occasionally, the liver . The primary symptoms are anemia, pancytopenia, and splenomegaly .
Hairy cell leukemia is a rare disorder, accounting for only 2% of all cases of leukemia  . It is a very treatable form of blood malignancy. Its diagnosis and differentiation from other forms of leukemia is of prime importance so that appropriate treatment is instituted as soon as possible.
The etiology of hairy cell leukemia is not known. But exposure to chemicals and radiation has been implicated. The highest incidence of Hairy cell leukemia is seen in middle-aged men . It is five times as prevalent in men as in women  . With chemotherapy complete remission occurs in about 90% of patients. The disease may be mild and slowly progressive so that patients do not need treatment. Complications include recurrent and life threatening infections, severe anemia, bleeding, and ruptured spleen.
What is hairy cell leukemia?
Hairy cell leukemia is a rare, highly treatable form of leukemia, blood cell cancer. Leukemia is a blood disorder where abnormal white blood cells are produced instead of normal cells. The malignant cells in this disease are called hairy cells because of the hair-like protrusions on the surface of the cell. In hairy cell leukemia the abnormal cells also interfere with the production of all blood cell types, red blood cells, white blood cells, and platelets.
What are the symptoms?
The symptoms are the result of the suppression of normal blood cells. They include:
What causes hairy cell leukemia?
The cause of hairy cell leukemia is not known. Exposure to toxic chemicals and radiation have been suspected but not proven to cause the disease.
Who gets hairy cell leukemia?
Anyone can get hairy cell leukemia, however it occurs most often in middle aged or elderly Caucasian men. The mean age at diagnosis is 50 years. The incidence in men is 5 times as high as in women.
How is it diagnosed?
Diagnosis is based on the results of the physical examination, blood tests, bone marrow biopsy and CT scan. The initial suspicion may occur with a routine blood test. Confirmation is based on the presence of characteristic malignant white blood cells called hairy cells in the bone marrow.
How is hairy cell leukemia treated?
Hairy Cell leukemia can be treated with intravenous medications that interfere with the production of the abnormal cells. Complete remission occurs in nearly 90% of patients. Usually only one course of treatment is necessary. However relapse occurs in approximately 30% of patients. Relapse can be treated with another course of treatment with a 90% success rate.
What are the complications?
The complications of hairy cell leukemia are due to the decrease in the production of normal blood cells. They include: