Chronic Lymphocytic Leukemia

Definition

Chronic lymphocytic leukemia (CLL) is a clonal malignancy of mature B lymphocytes characterized by accumulation of small, functionally incompetent lymphocytes in blood, bone marrow, lymph nodes, and spleen. It is the most common leukemia in adults in Western countries.

Epidemiology

• Most common leukemia in adults in Western countries
• Median age at diagnosis: 65–70 years
• Male predominance (male:female ratio ~1.5–2:1)
• Incidence lower in Asian populations
• Often diagnosed incidentally through routine blood tests showing lymphocytosis

Etiology

• Exact cause unknown; multifactorial
• Genetic abnormalities: deletion 13q14, 11q22–23, 17p13 (TP53), trisomy 12
• Inherited susceptibility may play a minor role
• Environmental exposures: benzene, herbicides, ionizing radiation (less clearly established)
• Association with autoimmune disorders in some cases

Pathophysiology

• Clonal proliferation of mature B lymphocytes with impaired apoptosis
• Accumulation in peripheral blood, bone marrow, lymph nodes, and spleen
• Defective immune function leading to hypogammaglobulinemia
• Autoimmune complications: hemolytic anemia, thrombocytopenia
• Disease progression varies from indolent to aggressive depending on genetic features and molecular markers