ABSTRACT
An intact defense system offers protection against infections through a complex interrelationship of protecting surfaces, cells, and soluble factors. A good general condition, optimal nutritional status, and normal organ function, together with all components of the cellular and humoral immune system, provide adequate protection against pathogenic microorganisms. There are fundamental differences between hematologic malignancies and solid tumors which affect the incidence as well as the severity of infectious complications concerned. Leukemias and lymphomas reside by definition within the immune system itself, exerting a dual deleterious effect. The malignant population interferes with and supplants the immunocompetent elements at their original location. Hemorrhages, inevitable during the course of acute leukemia, may impede organ function and facilitate the growth of microorganisms that may be present. The effects of the various noxious events that occur while treating a hematologic malignancy differ in severity and in primary targets. Moreover, such hazardous events exercise their impact dynamically as the degree of disturbance varies with time during or after a course of treatment. There is, in fact, a reciprocity: better supportive
care allows more aggressive therapy to achieve better cure rates at the price of peculiar, hitherto rare, infectious complications. Therefore, the survival of patients with a hematologic malignancy depends heavily on the quality of supportive care. Neutropenia is the most important risk factor, there being an inverse correlation between the number of circulating neutrophils and the frequency of infection. All patients with a neutrophil count of less than 100/µl for more than three weeks will develop fever, whereas only one-fifth of patients who are not neutropenic become febrile.1
