The infectious complications of chronic lymphocytic leukemia.

Infectious complications continue to have a major impact on the clinical course of patients with chronic lymphocytic leukemia despite advances in therapeutic approaches to this disease and supportive care. Although the pathogenesis of infection in these patients is multifactorial, systemic hypogammaglobulinemia is the major immune defect accounting for the increased risk of infection. Despite common knowledge of systemic immune defects in this population, information regarding mucosal immune function is minimal. In patients treated with conventional alkylating agents, infections commonly occur at mucosal sites, especially the respiratory tract, and organisms such as Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa are frequent isolates. The use of purine analogues as fludarabine has resulted in a change in this spectrum of infection, with the appearance of opportunistic infections caused by Pneumocystis, Listeria, Mycobacterium tuberculosis, Nocardia, Candida, Aspergillus, and herpesviruses. Further knowledge of the impact of chemotherapy on immune function, and of the immune defects in these patients, both inherent to the primary disease process and therapy-related, will aid in the formulation of better prophylactic and therapeutic interventions to reduce the risk of infection and improve the ultimate outcome of patients with chronic lymphocytic leukemia.