Thoracic fungal infections can be divided into two basic categories that are based on a balance between the virulence of the invading fungal organism and the immune status of the individual. Endemic fungi develop pathogenic infections when by sheer number of organisms they defeat the host's normal immune mechanism. Conversely, opportunistic fungal organisms possess lesser degrees of virulence; only rarely can they infect a normal immune system, but they are capable of establishing infections in immunoincompetent hosts (Figs. 90-1 and 90-2). Since the portal of entry for all fungal spores is through the airways, the pulmonary system is uniquely at risk for fungal infection compared with other visceral organs. The need for T-cell modulation to prevent graft rejection in organ transplant recipients places these individuals at particular risk for fungal infections. The proliferation of surviving transplant recipients has been accompanied by a rising incidence of fungal infections with novel yeast organisms that carry various degrees of antibiotic resistance.1
CT scan demonstrating multiple peripheral sites of fungal infection in an immunocompromised individual. (X-ray courtesy of Dr. F. Jacobson.)
CT scan demonstrating fungus balls in the right and left upper lung in an immunocompromised individual. (X-ray courtesy of Dr. F. Jacobson.)
Endemic fungal infections typically occur in regions specific to certain fungi. Denizens of these areas are at risk for the following infections: histoplasmosis, coccidioidomycosis, blastomycosis, and paracoccidioidomycosis (South American blastomycosis). Surgical treatments for these fungal infections have been well reviewed by Bethlem and colleagues,2 Robinson,3 and Johnson and Sarosi4 and are outlined below.
Histoplasma capsulatum is endemic in the midwestern region of the United States. Cases arise in a bandlike distribution along both sides of the Mississippi and Ohio River valleys. It is also found in certain regions of Central and South America, Africa, India, and Southeast Asia. The symptomatic infection usually is heralded by flulike symptoms, including fever, cough, headaches, and myalgias. The acute infection resolves spontaneously in 99% of individuals who have an immediate polymorphonuclear (PMN) and macrophage response, which isolates but does not destroy the fungus. If the inoculum is sufficiently large, the initial immune response may create a clinical scenario of acute respiratory distress syndrome. The initial response is followed by a chronic phase in which there is granuloma formation with fungal destruction by a delayed cell-mediated response. If the cell-mediated response is muted or absent, there may be progressive dissemination affecting mucosal surfaces, liver, spleen, adrenal gland, and meninges with multiorgan system failure.
The fungus is found in soil that has been contaminated with bird or bat droppings. Approximately 80% of populations in areas of endemic disease skin-test positive for exposure to the fungus.5 The mode of transmission ...