Viral opportunistic infections in patients with cancer usually represent symptomatic reactivation from latency facilitated by cancer-associated or therapy-associated cellular immunodeficiency. Herpes simplex virus (HSV) can cause severe and prolonged mucocutaneous infection or disseminated disease. Cytomegalovirus (CMV) can cause focal disease in immunocompromised persons, especially in stem cell transplant patients. Manifestations of CMV disease include hepatitis, pneumonitis, esophagitis, encephalitis, and enteritis with gastrointestinal ulcerations. Reactivation of Epstein-Barr virus (EBV) is associated with posttransplant lymphoproliferative disorder. Varicella zoster virus (VZV) can cause serious primary infection in susceptible persons, often with accompanying encephalitis, hepatitis, or, most ominously, pneumonitis. Zoster also can reactivate during chemotherapy and may be disseminated.
Chemotherapeutic agents target rapidly dividing cells, especially myeloproliferative cells, which cause myelosuppression.Children receiving allogeneic transplants are at greater riskfor infection than children receiving autologous transplants.Prolonged time to hematologic engraftment is a significantrisk factor for infection in these patients. Children receiving stem cell or organ transplants have significantly greaterimmunosuppression as a consequence of the myeloablative conditioning regimens. Foreign bodies (shunts, centralvenous catheters) interfere with cutaneous barriers againstinfection and together with neutropenia or immunosuppression increase the risk of bacterial or fungal infections (seeChapter 121).
The relative rate of infection in patients with cancer at admission or during hospitalization is 10% to 15%. The most frequently infected sites, in descending order, are the respiratory tract, the bloodstream, surgical wounds, and the urinary tract.
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Fever is the most common, and sometimes the only, presenting symptom of serious infection in cancer and transplant patients. The presence of fever with neutropenia, even in the absence of other signs or symptoms, demands prompt evaluation because of the potential for life-threatening infection. Despite being immunocompromised, these patients develop fever and some typical signs and symptoms associated with infections. All symptoms and signs should be evaluated thoroughly. However, some symptoms may be absent based on the underlying immunodeficiency. For example, in the absence of neutrophils to contain and induce localized signs of inflammation, determination of the source of infection by physical examination is often difficult. Chest findings may be absent, despite pneumonia, and revealed only by chest radiograph at presentation or when the neutrophil count recovers.
Assessing fever and neutropenia in immunocompromised persons requires blood cultures for bacterial and fungal pathogens obtained by peripheral venipuncture and from all lumens of any indwelling vascular catheters. A complete blood count with differential, C-reactive protein, complete chemistry panel, culture of urine and Gram staining/culture of potential sites of specific infection found during history and physical should be performed. Antigen tests, especially for serum cryptococcal antigen, should be considered. Chest radiographs are important to assess for the presence of pulmonary infiltrates. Specialized imaging studies, such as the CT or MRI, can be useful in selected cases, such as with suspected sinusitis or intra-abdominal infection, or to further delineate the location and extent of abnormalities seen on plain radiographs. Sinus infection with bacteria, Aspergillus, or Zygomycetes is common in neutropenic hosts and may be detected only on the CT scan.