Fungal Infections of Respiratory Tract Final Section

His toplasma capsulatum var. capsulatum, Blas tomyces dermatitidis, Coccidioides immitis, Paracoccidioides brasiliensis, and Penicillium marnefei are endemic dimorphic fungi that may infect the respiratory tract. Sporothrix schenkeii, which manifes ts the typical thermal dimorphism of the endemic dimorphic organisms, does not seem to follow a geographically deined endemic pattern of dis tribution. Mos t infections with any of these fungi are initiated by inhalation of conidia in nature. The pulmonary infection may be asymptomatic and resolve spontaneously, but reactivation may occur subsequently. Any of these fungi may disseminate from the lungs to other organs. These fungi routinely infect persons with apparently normal immunity and hence are named primary fungal pathogens. The fungi usually are contained by alveolar macrophages which are modulated by T lymphocytes, producing granulomatous inlammatory response for H. capsulatum, P. brasiliensis, and P. marnefei. A combined acute or pyogenic and chronic inlammatory response is often observed with C. immitis and B. dermatitidis. More than 95% of cases of his toplasmosis, coccidioidomycosis, and paracoccidioidomycosis are es timated to be selflimiting. In mos t cases the only evidence of infection is the development of an immune response, which is manifes ted by the production of speciic antibodies, development of precipitins and complement-ixing antibodies. The small percentage of these events that advance to progressive pulmonary infection or clinically overt disseminated infection are often associated with predisposing risk factors, particularly underlying defects in HIV-infected hos ts or patients receiving corticos teroids. The dimorphic fungi that cause sys temic mycoses are identiied by direct microscopic examination of specimens, by isolation and characterization of the fungus in cultures, by DNA probing of isolates, or by demons tration of speciic exoantigens produced in culture.