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An infectious disease of the lung, with occasional hematogenous spread, caused by various Aspergillus spp, especially A. fumigatus. A noninvasive pulmonary disorder may also occur as an allergic reaction to A. fumigatus or other species.
Etiology, Incidence, and Pathology
Aspergillus spp are some of the most common fungi in the human environment. They are frequently found in decaying vegetation (compost heaps), in insulating materials in walls and ceilings, around steel girders (to lessen condensation) in operating pavilions (often causing postoperative infections), and in patient rooms on television control knobs, IV pumps, tables, and beds. In numerous studies, species are variably commensals in the mouth, stool, or skin.
Superficial infections are uncommon, with the questionable exception of the ear canal. The fungus, an opportunist, appears after antibacterial or antifungal therapy (to which it is usually resistant) in bronchi damaged by bronchitis, bronchiectasis, or TB. The fungus ball (aspergilloma), a characteristic form of the disease, is composed of a tangled mass of hyphae, fibrin, exudate, and a few inflammatory cells. It is not usually invasive but gradually enlarges in bronchi or cavitations affected or caused by bronchiectasis or TB.
Invasive disease (septicemia) is seen in patients immunocompromised by specific diseases or treatments such as malignancy. Aspergillosis occurs especially frequently in recipients of heart and liver transplants. (However, because of its infrequency in AIDS patients, aspergillosis is not a defining disease.) In invasive disease, the tissue reaction at sites of fungal impaction and multiplication is usually suppurative. Occasionally granulomas surround hyphal fragments. Lesions are most commonly found in the brain and kidneys.
Symptoms and Signs
In otitis externa the only symptoms are itching, occasionally painful irritation, and a spot on the pillow from drainage (usually minimal).
The fungus ball is usually asymptomatic and discovered only on a chest film, appearing as a dense round ball, capped by a slim meniscus of air, in a cavity. The principal symptom is hemoptysis, frequently recurrent, occasionally severe, and rarely (but tragically) fatal.
In invasive (septicemic) disease, the symptoms seem no less intense or frequent than in bacterial septicemia and include fever, chills, shock, skin lesions, consumption coagulopathy, and multiple organ failure (azotemia, acidosis, hypoxia, jaundice, delirium). Emboli are common in endocarditis. With leukemia, organ transplantation, or corticosteroid or immunosuppressive therapy, the clinical picture is a typical septicemia, and dissemination to the brain and kidneys may occur.
Chronic necrotizing pulmonary aspergillosis is related to chronic suppurative lung disease.
Diagnosis
When otitis externa is caused, rarely, by Aspergillus (usually A. niger), diagnosis depends on culture. Diagnosis of fungus ball by culture of respiratory secretions is very difficult, probably because the local intrabronchial or intracavitary reaction is so infrequently inflammatory.
In invasive (septicemic) disease, Aspergillus spp have been similarly difficult to culture from blood specimens, partly because of the fulminant, brief, and fatal course of the disease. Even in endocarditis, in which bacteremia is considered to be constant, the fungus is almost never cultured from blood specimens and only occasionally from resected emboli.
Prognosis and Treatment
Otitis externa responds to nonfungal solution (ie, aluminum acetate [Burow's]). The fungus ball must be resected, though intravascular (bronchial artery) coagulation therapy has been tried occasionally. In invasive (systemic) disease, amphotericin B should be given IV (see General Therapeutic Principles, above), although tolerated doses are usually ineffective, since most strains are resistant. Ketoconazole has not been any more effective. Itraconazole appears more active in vitro against more isolates and has been successful in a few cases; controlled comparative studies may demonstrate that it is the best drug.
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