Chapter 082. Infections in Patients with Cancer (Part 9)

Diffuse interstitial infiltrates suggest viral, parasitic, or Pneumocystis pneumonia. If the patient has a diffuse interstitial pattern on chest x-ray, it may be reasonable to institute empirical treatment with TMP-SMX (for Pneumocystis) and a quinolone (for Chlamydophila, Mycoplasma, and Legionella) or an erythromycin derivative (e.g., azithromycin) while considering invasive diagnostic procedures. Noninvasive procedures, such as staining of sputum smears for Pneumocystis, serum cryptococcal antigen tests, and urine testing for Legionella antigen, may be helpful. In transplant recipients who are seropositive for cytomegalovirus (CMV), a determination of CMV load in the serum should be considered. Viral load studies (which allow...
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Chapter 082. Infections in Patients with Cancer (Part 9) Chapter 082. Infections in Patients with Cancer (Part 9) Diffuse interstitial infiltrates suggest viral, parasitic, or Pneumocystispneumonia. If the patient has a diffuse interstitial pattern on chest x-ray, it may bereasonable to institute empirical treatment with TMP-SMX (for Pneumocystis) anda quinolone (for Chlamydophila, Mycoplasma, and Legionella) or an erythromycinderivative (e.g., azithromycin) while considering invasive diagnostic procedures.Noninvasive procedures, such as staining of sputum smears for Pneumocystis,serum cryptococcal antigen tests, and urine testing for Legionella antigen, may behelpful. In transplant recipients who are seropositive for cytomegalovirus (CMV),a determination of CMV load in the serum should be considered. Viral loadstudies (which allow physicians to quantitate viruses) have superseded simplemeasurement of serum IgG, which merely documents prior exposure to virus.Infections with viruses that cause only upper respiratory symptoms inimmunocompetent hosts, such as respiratory syncytial virus (RSV), influenzaviruses, and parainfluenza viruses, may be associated with fatal pneumonitis inimmunocompromised hosts. An attempt at early diagnosis by nasopharyngealaspiration should be considered so that appropriate treatment can be instituted. Bleomycin is the most common cause of chemotherapy-induced lungdisease. Other causes include alkylating agents (such as cyclophosphamide,chlorambucil, and melphalan), nitrosoureas [carmustine (BCNU), lomustine(CCNU), and methyl-CCNU], busulfan, procarbazine, methotrexate, andhydroxyurea. Both infectious and noninfectious (drug- and/or radiation-induced)pneumonitis can cause fever and abnormalities on chest x-ray; thus, thedifferential diagnosis of an infiltrate in a patient receiving chemotherapyencompasses a broad range of conditions (Table 82-7). Since the treatment ofradiation pneumonitis (which may respond dramatically to glucocorticoids) ordrug-induced pneumonitis is different from that of infectious pneumonia, a biopsymay be important in the diagnosis. Unfortunately, no definitive diagnosis can bemade in ~30% of cases, even after bronchoscopy. Open-lung biopsy is the gold standard of diagnostic techniques. Biopsyvia a visualized thoracostomy can replace an open procedure in many cases. Whena biopsy cannot be performed, empirical treatment can be undertaken with aquinolone or erythromycin (or an erythromycin derivative such as azithromycin)and TMP-SMX (in the case of diffuse infiltrates) or with amphotericin B or otherantifungal agents (in the case of nodular infiltrates). The risks should be weighedcarefully in these cases. If inappropriate drugs are administered, empiricaltreatment may prove toxic or ineffective; either of these outcomes may be riskierthan biopsy. Cardiovascular Infections Patients with Hodgkins disease are prone to persistent infections bySalmonella, sometimes (and particularly often in elderly patients) affecting avascular site. The use of IV catheters deliberately lodged in the right atrium isassociated with a high incidence of bacterial endocarditis, presumably related tovalve damage followed by bacteremia. Nonbacterial thrombotic endocarditis hasbeen described in association with a variety of malignancies (most often solidtumors) and may follow bone marrow transplantation as well. The presentation ofan embolic event with a new cardiac murmur suggests this diagnosis. Bloodcultures are negative in this disease of unknown pathogenesis. Endocrine Syndromes Infections of the endocrine system have been described inimmunocompromised patients. Candida infection of the thyroid may be difficultto diagnose during the neutropenic period. It can be defined by indium-labeledWBC scans or gallium scans after neutrophil counts increase. CMV infection cancause adrenalitis with or without resulting adrenal insufficiency. The presentationof a sudden endocrine anomaly in an immunocompromised patient may be a signof infection in the involved end organ. Musculoskeletal Infections Infection that is a consequence of vascular compromise, resulting ingangrene, can occur when a tumor restricts the blood supply to muscles, bones, orjoints. The process of diagnosis and treatment of such infection is similar to that innormal hosts, with the following caveats: 1. In terms of diagnosis, a lack of physical findings resulting from a lack ofgranulocytes in the granulocytopenic patient should make the clinician moreaggressive in obtaining tissue rather than relying on physical signs. 2. In terms of therapy, aggressive debridement of infected tissues may berequired, but it is usually difficult to operate on patients who have recentlyreceived chemotherapy, both because of a lack of platelets (which results inbleeding complications) and because of a lack of WBCs (which may lead tosecondary infection). A blood culture positive for Clostridium perfringens—anorganism commonly associated with gas gangrene—can have a number ofmeanings (Chap. 135). Bloodstream infections with intestinal organisms such asStreptococcus bovis and C. perfringens may arise spontaneously from lowergastrointestinal lesions (tumor or polyps); alternatively, these lesions may beharbingers of invasive disease. The clinical setting must be considered in order todefine the appropriate treatment for each case.