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These infections result from inhalation of the spores of dimorphic fungi that have their mold forms in the soil. Within the lungs, the spores differentiate into yeasts or other specialized forms, such as spherules.

Most lung infections are asymptomatic and self-limited. However, in some persons, disseminated disease develops in which the organisms grow in other organs, cause destructive lesions, and may result in death. Infected persons do not communicate these diseases to others.

Important features of the systemic fungal diseases are described in Table 49–1. Systemic fungi are also called endemic fungi because they are endemic (localized) to certain geographic areas.

TABLE 49–1Important Features of Systemic Fungal Diseases

Additional information regarding the clinical aspects of infections caused by the fungi in this chapter is provided in Part IX, entitled Infectious Diseases.



Coccidioides immitis and Coccidioides posadasii cause coccidioidomycosis. The clinical manifestations of disease caused by these two species are the same, but the geographical distribution differs. For simplicity, the original species name, C. immitis, will be used most often in this chapter.


Coccidioides species are dimorphic fungi that exist as a mold in soil and as a spherule in tissue (Figure 49–1). C. immitis and C. posadasii are distinguished by genotyping but not by routine diagnostic tests in the clinical laboratory.


Stages of Coccidioides immitis. A: Arthrospores form at the ends of hyphae in the soil. They germinate in the soil to form new hyphae. If inhaled, the arthrospores differentiate into spherules. B: Endospores form within spherules in tissue. When spherules rupture, endospores disseminate and form new spherules. (Reproduced with permission from Brooks GF, Butel JS, Ornston LN: Jawetz, Melnick & Adelberg’s Medical Microbiology, 20th ed. New ...

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