Autoimmune diseases may also go into remission after treatment of HCL. Epidemiology
This disease is rare, with fewer than 1 in 10,000 people being diagnosed with HCL during their lives. Men are four to five times more likely to develop hairy cell leukemia than women. In the United States, the annual incidence is approximately 3 cases per 1,000,000 men each year, and 0.6 cases per 1,000,000 women each year.Most patients are white males over the age of 50, although it has been diagnosed in at least one teenager. It is less common in people of African and Asian descent compared to people of European descent. It does not appear to be hereditary, although occasional familial cases that suggest a predisposition have been reported, usually showing a common Human Leukocyte Antigen (HLA) type. Research directions
The Hairy Cell Leukemia Consortium was founded in 2008 to address researchers concerns about the long-term future of research on the disease. Partly because existing treatments are so successful, the field has attracted very few new researchers. In 2013 the Hairy Cell Leukemia Foundation was created when the Hairy Cell Leukemia Consortium and the Hairy Cell Leukemia Research Foundation joined. The HCLF is dedicated to improving outcomes for patients by advancing research into the causes and treatment of hairy cell leukemia, as well as by providing educational resources and comfort to all those affected by hairy cell leukemia.Three immunotoxin drugs have been studied in patients at the NIH National Cancer Institute in the U.S.:  BL22, HA22 and LMB-2.
About 10% of people with HCL have this variant form of the disease, representing about 60-75 new cases of HCL-V each year in the U.S. While classic HCL primarily affects men, HCL-V is more evenly divided between males and females. While the disease can appear at any age, the median age at diagnosis is over 70.Similar to B-cell prolymphocytic leukemia (B-PLL) in chronic lymphocytic leukemia, HCL-V is a more aggressive disease. Historically, it has been considered less likely to be treated successfully than is classic HCL, and remissions have tended to be shorter. The introduction of combination therapy with concurrent rituximab and cladribine therapy, though, has shown excellent results in early follow-up. As of 2016, this therapy is considered the first-line treatment of choice for many people with HCL-V.Many older treatment approaches, such as interferon-alpha, the combination chemotherapy regimen "CHOP", and common alkylating agents such as cyclophosphamide, showed very little benefit. Pentostatin and cladribine administered as monotherapy (without concurrent rituximab) provide some benefit to many people with HCL-V, but typically induce shorter remission periods and lower response rates than when they are used in classic HCL. More than half of people respond partially to splenectomy.In terms of B-cell development, the prolymphocytes are less developed than are lymphocytes or plasma cells, but are still more mature than their lymphoblastic precursors.