Hairy cell leukemia is a cancer of lymphocytes (B cells) that leads to low blood counts.

Hairy cell leukemia (HCL) is an uncommon cancer of the blood. It can be one of the causes of low numbers of normal blood cells. The disease is caused by the abnormal growth of B cells that can look "hairy" under the microscope because they have fine projections coming from their surface.

The cause of this disease is unknown. It affects men 5 times more often than women, and the average age of onset is 55. Hairy cell leukemia is rare and only accounts for about 2% of the leukemias diagnosed each year.

• Weakness
• Fatigue
• Weight loss
• Easy bruising or bleeding
• Recurrent infection
• Excessive sweating (especially at night)
• Swollen lymph glands
• Early satiety (feeling full after eating only a small amount)

• A physical examination can reveal an enlarged spleen and/or liver.
• A bone marrow biopsy shows hairy cells.
• A peripheral blood smear may show hairy cells.
• A special test done on blood or bone marrow cells (tartrate-resistant acid phosphatase) can confirm the diagnosis.
• An abdominal CT scan shows an enlarged spleen and liver.
• A CBC shows low white blood cell count, low red cell count, and low platelets.

Early in the course of the disease, no treatment may be necessary. Some patients may need an occasional blood transfusion.

If treatment is needed because of very low blood counts, a variety of chemotherapy drugs (cladribine, pentostatin) can be used. Interferon is also used. In the majority of cases these drugs can produce a remission (complete relief from the disease) that lasts for many years. It is unclear if chemotherapy will cure the disease, however, because most patients will relapse over time.

The removal of the spleen may improve blood counts, but is unlikely to cure the disease. Symptomatic treatment of infections with antibiotics or low blood counts with growth factors and transfusions may be required.