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Infection with the human immunodeficiency virus (HIV) induces a secondary immune deficiency, rendering the host susceptible to infection. The immunosuppressive combination of HIV infection in the setting of the immature pediatric immune system represents an ideal medium for opportunistic pathogens to thrive and the challenge rests with the pediatrician to diagnose, treat, and prevent these infections.
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Infections in HIV-infected children occur in two broad groups: opportunistic infections (OI) and nonopportunistic infections. OI are defined by the Centers for Disease Control and Prevention (CDC) disease classification of pediatric HIV infection (see Table 53–1 in Chapter 53).1,2 Nonopportunistic infections represent all other known pathogens. The description of an infection as an OI is helpful in defining an AIDS-related illness (ARI), but does not mean that the nonopportunistic infections are any less common or severe.
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In the United States, earlier detection of HIV infection through screening of pregnant women as well as the widespread use of highly active antiretroviral therapy (HAART) and pneumocystis prophylaxis have dramatically decreased the rates of AIDS-related OI in children. These advances have converted pediatric HIV in most children from an acute life-threatening condition to a chronic illness. Despite these advances, OI continue to occur in this population.
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The epidemiology of infections in the HIV-infected child in the United States has dramatically altered after the introduction of HARRT in 1996 and its subsequent widespread use. In the pre-HAART era, the five most common OI, which all occurred at an event rate of greater than 1 per 100 patient-years, were serious bacterial infection, herpes zoster, disseminated Mycobacterium avium complex (MAC), Pneumocystis jiroveci pneumonia (PCP, formerly called Pneumocystis carinii pneumonia), and mucosal candidiasis (Table 54–1).3 Other less common opportunistic conditions included cytomegalovirus (CMV) disease particularly retinitis, tuberculosis, invasive fungal disease other than mucosal candidiasis, toxoplasmosis, and progressive multifocal leukoencephalopathy. In the HAART era, opportunistic illnesses occur mainly in two settings: as the presenting sign of a child in whom the diagnosis of HIV was previously unknown and in known HIV-infected children with a persistently low CD4+ T-lymphocyte percentage.4 Following the introduction of HAART, the four most common OI, all of which occur at a lower event rate than the pre-HAART era, are now bacterial pneumonia, herpes zoster, oral candidiasis, and dermatophyte infections (Table 54–1).5
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