Infectious complications in chronic lymphocytic leukaemia

Infections are the major cause of morbidity and mortality in patients with chronic lymphocytic leukemia (CLL). Predisposition to infection in CLL is mediated through various abnormalities including both the immune defects inherent in the primary disease (impairment in humoral and cellular immunity) and in the further immunosuppression related to the management of CLL. Hypogammaglobulinemia is probably the most important immune defect in terms of risk of severe bacterial infections, its frequency and severity progressing with the duration of the disease. Newer antineoplastic agents such as purine analogues, especially when used in previously treated patients, may be associated with a new spectrum of pathogens (Listeria monocytogenes, Pneumocystis carinii, cytomegalovirus, herpes simplex virus, and mycobacteria) involving T-cell dysfunction. In this review we focus on the clinical characteristics of infections in CLL and on the risk factors involved in the pathogenesis of this complication. Furthermore, we describe the evolving patterns of infections associated with purine analogues and discuss the currently accepted approaches to prophylaxis and treatment.