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Chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a disorder of morphologically mature but immunologically less mature lymphocytes and is manifested by progressive accumulation of these cells in the blood, bone marrow, and lymphatic tissues.


CLL is the most common leukemia in adults in western countries, and it accounts for approximately 25% of all leukemias.

The incidence is also age dependent, with an increase from 5.2 per 100,000 persons older than 50 years to 30.4 per 100,000 in people older than 80.

Estimated new cases and deaths from chronic lymphocytic leukemia (CLL) in the United States in 2005:

  • New cases: 9,730.

  • Deaths: 4,600.


The male to female ratio is 2:1. This trend appears to be lost with age; the male-to-female ratio is 2:1 for patients < 50 years old, compared with 1.1:1.0 for those ≥ 75 years old.


CLL occurs primarily in middle-aged and elderly individuals, with increasing frequency in successive decades of life. The median age at diagnosis is 70 years.

Race and ethnicity

In the American population, the incidence of CLL is similar in different races.


The incidence is much lower in Asia (Japan, Korea, and China), Latin America, and Africa than in the United States.

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