Chronic Lymphocytic Leukemia
This booklet provides information about chronic lymphocytic leukemia (CLL) for patients and their families. Brief descriptions of normal blood and bone marrow and the lymphatic system are provided to help readers better understand the CLL-specific information in the booklet.
Chronic lymphocytic leukemia (CLL) results from an acquired (not present at birth) change (mutation) to the DNA of a single marrow cell that develops into a lymphocyte. In 95 percent of people with CLL, the change occurs in a B lymphocyte. In the other 5 percent of people with CLL, the cell that transforms from normal to leukemic has the features of a T lymphocyte or an NK cell. Thus, any of the three major types of lymphocytes (T cells, B cells or NK cells) can undergo a malignant transformation that causes diseases related to B-cell CLL.