BACKGROUND

Coccidioidomycosis, first described over a century ago by Alejandro Posadas, is a disease of protean manifestations endemic primarily to ecologic regions of the Western Hemisphere characterized as the Lower Sonoran Life Zone. This includes areas in the southwestern United States (California, Arizona, western Texas, and selected areas of New Mexico, Nevada, and Utah), northern Mexico, and scattered foci in Central and South America. Within these general endemic areas the incidence of coccidioidomycosis may vary significantly due to geographic pockets and climatic conditions particularly favorable for infection. The etiologic agent, classically known as Coccidioides immitis, is a dimorphic fungus that grows in its soil reservoir in the mycelial (mould) phase. Under appropriate conditions, infectious spores, dubbed arthroconidia, disarticulate from mycelia and are carried airborne and inhaled, reaching the alveoli of the host. There the organism converts to the parasitic spherule phase, which reproduces by a process characteristic of Coccidioides species known as endosporulation. Infection usually is controlled locally and confined to the site(s) of initial alveolar implantation. In some cases, such as if the infecting inoculum is large and or the host is unable to mount an effective immune response, a chronic pulmonary infection may result or infection may go on to spread within the thorax or distantly, via the lymphatics and bloodstream. Disseminated (extrapulmonary) infection, especially when it involves the meninges, carries with it considerable potential for morbidity and mortality and therefore must always be treated.