Rare Pediatrics News

Disease Profile

Hairy cell leukemia

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

1-9 / 100 000

US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Leukemic reticuloendotheliosis; HCL


Blood Diseases; Rare Cancers


Hairy cell leukemia is a rare, slow-growing cancer of the blood in which the bone marrow makes too many B cells (lymphocytes), a type of white blood cell that fights infection. The condition is named after these excess B cells which look 'hairy' under a microscope. As the number of leukemia cells increases, fewer healthy white blood cells, red blood cells and platelets are produced.[1][2] The symptoms include a large spleen (splenomegalia) but without an increase of lymph nodes, and general symptoms such as fever, night sweats, fatigue, weight loss. Blood exams show the decreased number of blood cells and platelets. The diagnosis can be made with the biopsy of the bone marrow, blood exams showing antigens that are released by the B-cells. The leukemia cells show an specific change (variation or mutation) in a gene involved in cell growth, the BRAF gene, that increases the growth and spread of cancer cells. The decision to treat depends in whether or not symptoms, splenomegaly, or other complications are present. About 10% of all patients will never require treatment.[3][4] The cause is still unknown. While there is no cure, treatment can lead to remission which can last for years.[1][2]


FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • MayoClinic.com has an information page on Hairy cell leukemia.
  • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
  • The National Cancer Institute provides the most current information on cancer for patients, health professionals, and the general public.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Hairy cell leukemia. Click on the link to view a sample search on this topic.


  1. Hairy cell leukemia. MayoClinic.com. 2015; https://www.mayoclinic.org/es-es/diseases-conditions/hairy-cell-leukemia/symptoms-causes/syc-20372956.
  2. Dugdale DC & Mason JR. Hairy cell leukemia. MedlinePlus. 2017; https://www.nlm.nih.gov/medlineplus/ency/article/000592.htm.
  3. Hairy Cell Leukemia Treatment (PDQ®)–Health Professional Version. American Cancer Society. 2016; https://www.cancer.gov/types/leukemia/hp/hairy-cell-treatment-pdq#section/_1.
  4. Tallman MS. Treatment of hairy cell leukemia. UpToDate. November 27, 2017; https://www.uptodate.com/contents/treatment-of-hairy-cell-leukemia#H5.