Overview of Infections in the Immunocompromised Host

This chapter briefly reviews the components of host defense and the types of infections that are most likely to occur with specific defects in the defense mechanisms. It describes the infections that occur in patients with a variety of primary and secondary immunodeficiency disorders so as to provide illustrative examples. Patients on potent immunosuppressive regimens are at risk for fungal infections. The majority of these infections are caused by Candida and Aspergillus species. A variety of fungal infections that are kept in check by granuloma formation have also been reported for these patients, the most common of which are disseminated histoplasmosis, cryptococcosis, coccidioidomycosis, and aspergillosis. The period from 1 to 6 months after transplantation is the critical time after transplantation during which infections unique to the immunocompromised hosts most often arise. Based upon information provided in the chapter, the types of infections, the drugs being used, and other symptoms should help to focus the laboratory workup on specific parts of the immune system. Immunocompromised hosts have an increased susceptibility to infections for a wide variety of reasons. The chapter lays the groundwork for understanding why an individual patient may have an increased susceptibility to specific types of pathogens.