ABSTRACT
Much laboratory and clinical research has been conducted in the area of infection and host defense mechanisms, leading to important advances in diagnostic testing and an explosion in the number of agents available for the treatment of infections. Nonetheless, infectious complications remain the major cause of morbidity and mortality in patients undergoing chemotherapy for acute leukemia, with 41-92% of all patients with acute myeloid leukemia (AML) developing infectious complications during therapy.1-6
Infections are also problematic for patients with other hematological malignancies, due either to the underlying disease itself or to therapy-induced perturbations in host defense systems. The ability of the host to protect itself from infection depends on the availability of adequate numbers of functionally competent phagocytic cells as well as the integrity of skin and mucosal barriers to invasion by infectious agents (Table 2.1). In addition, humoral and cellular immune defense systems represent an important level of resistance to infections. Dose-intensive therapies, which are being used increasingly for the treatment of acute
leukemia and other hematological malignancies, result in profound neutropenia and disruption of skin and mucosal barriers. In addition, dose-intensive therapies disturb humoral and cellular immune mechanisms, although these defects are harder to quantitate than neutropenia and mucositis and are thus often overlooked by clinicians and other caregivers. Intensive therapy also introduces other challenges to the clinical management of acute leukemia, such as the need for hospitalization, indwelling venous catheters, and transfusion support (Table 2.2). Because of the varying impact of these problems on patients and differences in the basic biology of the hematological malignancies, a broad range of infectious syndromes is encountered during the care of these patients (Table 2.3). This chapter focuses on the defects in host defense mechanisms that are caused either by disease itself or by the different treatment regimens employed, and the influence that these defects have on the incidence and type of infectious illnesses encountered in patients with hematological malignancies.
