Chapter 082. Infections in Patients with Cancer (Part 8)

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Brain Masses Mass lesions of the brain most often present as headache with or without fever or neurologic abnormalities. Infections associated with mass lesions may be caused by bacteria (particularly Nocardia), fungi (particularly Cryptococcus or Aspergillus), or parasites (Toxoplasma). Epstein-Barr virus (EBV)–associated lymphoproliferative disease may also present as single or multiple mass lesions of the brain. A biopsy may be required for a definitive diagnosis. Pulmonary Infections Pneumonia (Chap. 251) in immunocompromised patients may be difficult to diagnose because conventional methods of diagnosis depend on the presence of neutrophils. Bacterial pneumonia in neutropenic patients may present without purulent sputum—or, in fact,...

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Chapter 082. Infections in Patients with Cancer (Part 8) Brain Masses Mass lesions of the brain most often present as headache with or without fever or neurologic abnormalities. Infections associated with mass lesions may be caused by bacteria (particularly Nocardia), fungi (particularly Cryptococcus or Aspergillus), or parasites (Toxoplasma). Epstein-Barr virus (EBV)–associated lymphoproliferative disease may also present as single or multiple mass lesions of the brain. A biopsy may be required for a definitive diagnosis. Pulmonary Infections
Pneumonia (Chap. 251) in immunocompromised patients may be difficult to diagnose because conventional methods of diagnosis depend on the presence of neutrophils. Bacterial pneumonia in neutropenic patients may present without purulent sputum—or, in fact, without any sputum at all—and may not produce physical findings suggestive of chest consolidation (rales or egophony). In granulocytopenic patients with persistent or recurrent fever, the chest x- ray pattern may help to localize an infection and thus to determine which investigative tests and procedures should be undertaken and which therapeutic options should be considered (Table 82-7). The difficulties encountered in the management of pulmonary infiltrates relate in part to the difficulties of performing diagnostic procedures on the patients involved. When platelet counts can be increased to adequate levels by transfusion, microscopic and microbiologic evaluation of the fluid obtained by endoscopic bronchial lavage is often diagnostic. Lavage fluid should be cultured for Mycoplasma, Chlamydophila, Legionella, Nocardia, more common bacterial pathogens, and fungi. In addition, the possibility of Pneumocystis pneumonia should be considered, especially in patients with ALL or lymphoma who have not received prophylactic trimethoprim-sulfamethoxazole (TMP-SMX). The characteristics of the infiltrate may be helpful in decisions about further diagnostic and therapeutic maneuvers. Nodular infiltrates suggest fungal pneumonia (e.g., that caused by Aspergillus or Mucor). Such lesions may best be approached by visualized biopsy procedures.
Table 82-7 Differential Diagnosis of Chest Infiltrates in Immunocompromised Patients Cause of Pneumonia Infiltrate Infectious Noninfectious Localized Bacteria, Legionella, Local hemorrhage or mycobacteria embolism, tumor Nodular Fungi (e.g., Recurrent tumor Aspergillus or Mucor), Nocardia Diffuse Viruses (especially Congestive heart failure, CMV), Chlamydophila, radiation pneumonitis, drug-induced Pneumocystis, Toxoplasma lung injury, diffuse alveolar gondii, mycobacteria hemorrhage (described after BMT) Abbreviations: BMT, bone marrow transplantation; CMV,
cytomegalovirus. Aspergillus spp. (Chap. 197) can colonize the skin and respiratory tract or cause fatal systemic illness. Although Aspergillus may cause aspergillomas in a previously existing cavity or may produce allergic bronchopulmonary aspergillosis, the major problem posed by this genus in neutropenic patients is invasive disease due to A. fumigatus or A. flavus. The organisms enter the host following colonization of the respiratory tract, with subsequent invasion of the blood vessels. The disease is likely to present as a thrombotic or embolic event because of the organisms' ability to invade blood vessels. The risk of infection with Aspergillus correlates directly with the duration of neutropenia. In prolonged neutropenia, positive surveillance cultures for colonization of the nasopharynx with Aspergillus may predict the development of disease. Patients with Aspergillus infection often present with pleuritic chest pain and fever, which are sometimes accompanied by cough. Hemoptysis may be an ominous sign. Chest x-rays may reveal new focal infiltrates or nodules. Chest CT may reveal a characteristic halo consisting of a mass-like infiltrate surrounded by an area of low attenuation. The presence of a "crescent sign" on a chest x-ray or a chest CT scan, in which the mass progresses to central cavitation, is characteristic of invasive Aspergillus infection but may develop as the lesions are resolving.
In addition to causing pulmonary disease, Aspergillus may invade through the nose or palate, with deep sinus penetration. The appearance of a discolored area in the nasal passages or on the hard palate should prompt a search for invasive Aspergillus. This situation is likely to require surgical debridement. Catheter infections with Aspergillus usually require both removal of the catheter and antifungal therapy.