Leukemia, Chronic Lymphocytic



  • Chronic lymphocytic leukemia (CLL) is a monoclonal disorder characterized by a progressive accumulation of mature but functionally incompetent lymphocytes.
  • Based on percentage of prolymphocytes, the disease may be regarded as CLL (<10% prolymphocytes), prolymphocytic leukemia (PLL; >55%), or CLL/PLL (>10% and <55%).
  • Small lymphocytic lymphoma is a lymphoma variant of CLL.
  • System(s) affected: hematologic, lymphatic, immunologic



  • CLL represents the most common form of leukemia in adults in the United States with an estimated 21,050 new cases diagnosed in 2021.
  • In 2021, an estimated 4,320 adults in the United States died from CLL, which makes it the second leading cause of death among adults with leukemia in the United States after acute myeloid leukemia.
  • CLL primarily affects elderly individuals, median age of diagnosis being 70 years. Incidence continues to rise in those age >55 years.
  • Predominant sex: male > female (1.6:1)
  • The incidence is higher among Caucasians than among African Americans.

Etiology and Pathophysiology

  • The cell of origin in CLL is a clonal B cell arrested in the B-cell differentiation pathway, intermediate between pre–B cells and mature B cells. In the peripheral blood, these cells resemble mature lymphocytes.
  • Genetic mutations leading to disrupted function and prolonged survival of affected lymphocytes are suspected but not well known. The BCL2 proto-oncogene (suppressor of apoptosis or programmed cell death) is overexpressed in CLL.

Truly familial cases are exceedingly rare. CLL has been shown, however, to occur at higher frequency among first-degree relatives of patients with the disease, and several somatic gene mutations have been identified at significantly higher rates among CLL patients (1).

Risk Factors

The exact cause of CLL is uncertain. Possible chronic immune stimulation is suspected but is still being evaluated. Monoclonal B-cell lymphocytosis: 1% risk progression to CLL

General Prevention


Commonly Associated Conditions

  • Immune system dysregulation is common.
  • Autoimmune hemolytic anemia (AIHA)
  • Immune thrombocytopenia purpura (ITP)
  • Pure red cell aplasia (PRCA)

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