Hairy cell leukemia is a rare, slow-growing cancer of the blood in which the bone marrow overproduces B cells (lymphocytes). Lymphocytes are a type of blood cells that fight infection.

The excess B cells are abnormal and as the number of leukemia cells increases, fewer healthy white and red blood cells as well as platelets are produced.

Hairy cell leukemia occurs more commonly in middle-aged to older adults and it is more common in men than women.

Hairy cell leukemia is a chronic disease because it may never completely disappear although it may go into remission with proper treatment.



In some cases, there are no symptoms of hairy cell leukemia and a blood test for another disease may unintentionally reveal hairy cell leukemia.

On the other hand, symptoms of hairy cell leukemia may include:


  • Fatigue
  • Easy bruising
  • A feeling of fullness in the abdomen
  • Recurring infections
  • Weight loss
  • Weakness



The exact cause of hairy cell leukemia is unclear.

Cancer occurs when cells develop errors in the DNA. In hairy cell leukemia, mutations in the DNA cause the bone marrow stem cells to overproduce abnormal white blood cells. However, doctors are uncertain of the cause of the DNA mutations that cause hairy cell leukemia.


Risk factors

Possible risk factors for hairy cell leukemia include:


  • Exposure to radiation (working around X-rays or radiation therapy)
  • Exposure to chemicals (industrial and agricultural chemicals)
  • Exposure to sawdust (working with wood and sawdust)
  • Ethnicity (affects men of Ashkenazi Jewish ancestry more than other ethnic groups)



Untreated, progressive hairy cell leukemia may outnumber healthy blood cell, leading to the following complications:


  • Infections: low levels of white blood cells increase the risk of infections due to the inability to fight them off
  • Bleeding: low levels of platelets means low clotting factors. Low clotting factors cause difficulty to stop bleeding or easy bruising while very low platelet count can cause spontaneous bleeding.
  • Anemia: low levels of red blood cells indicate that less cells are available to carry oxygen throughout the body leading to fatigue.


Increased risk of second cancers

Studies have shown that people with hairy cell leukemia may have an increased risk of developing a second type of cancer. Second cancers more commonly found in people treated for hairy cell leukemia include non-Hodgkin lymphoma.