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Classic hairy cell leukemia
Hairy cell leukemia (HCL) is a rare type of leukemia in which abnormal B-lymphocytes are present in the bone marrow, spleen and peripheral blood. It is a slowly progressive chronic lymphocytic leukemia (CLL). The name comes from the abnormally shaped lymphocytes with hair-like projections.
ORPHA:58017Classification level: Disorder
- Leukemic reticuloendotheliosis
- Prevalence: 1-9 / 100 000
- Inheritance: -
- Age of onset: Adult
- ICD-10: C91.4
- OMIM: -
- UMLS: C0023443
- MeSH: D007943
- GARD: 6560
- MedDRA: 10019053
HCL accounts for 2% of all leukemia cases and the annual incidence has been estimated at 1 in 500,000. It affects men more often than women (5:1) and occurs most commonly in middle-age or older adults (average age of onset is 55).
Symptoms of HCL are related to the disruption of normal blood cell production. Low red cell production leads to anemia, low white cell production to increased infections, and low platelet counts to bleeding or easy bruising. Abdominal discomfort is a common symptom, resulting from hepatosplenomegaly. Splenomegaly is present in virtually all cases, and is classed as massive in more than 80% of cases. Hepatomegaly with mild liver dysfunction is found in 20% of cases and lymphadenopathy is found in 10% of cases. Complications include recurrent infections, bleeding, anemia and splenic rupture.
Etiology is unknown. Family history of blood cancers, Ashkenazi Jewish heritage, personal history of cancer, and exposure to radiation, chemicals and sawdust are considered as possible risk factors.
Diagnosis is based on the results of the physical examination, blood tests, bone marrow biopsy and CT scan.
Management and treatment
HCL can be treated with chemotherapy (2-chlorodeoxyadenosine, pentostatin) or biological therapy (interferon alpha, rituximab). In 2004, cladribine received EU marketing authorization as an Orphan drug for treatment for HCL. Complete or partial remission with chemotherapy is achieved in about 90% of patients. Splenectomy may be useful in patients with uncontrollable infections. In some cases, the disease is so mild and slow growing that patients do not require any treatment and remain stable for many years.
Most patients live 10 years or longer with the disease.