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Aspergillosis, caused by any of several species of Aspergillus, usually manifests in immunocompromised or debilitated hosts as necrotizing cavitary pulmonary lesions or as hematogenously disseminated foci in multiple organs. Aspergillus can also cause a hypersensitivity or allergic pneumonitis in immunocompetent hosts and in patients with chronic pulmonary diseases. This is referred to as allergic bronchopulmonary aspergillosis (ABPA) (eFig. 295.1).

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Ubiquitous in nature, Aspergillus spp are commonly found in soil, water, and on decaying vegetation. Human exposure to the spores of potentially pathogenic species, particularly A fumigatus, is unavoidable. Aspergillus fumigatus has been implicated in most of the disseminated and pulmonary infections, but A flavus and A niger, among others, have also been recovered as pathogens. Transmission occurs by inhalation of airborne spores that regularly contaminate the environment; human-to-human transmission or zoonotic transmission has not been documented. Patients with immunosuppression are at greatest risk, especially those who are being treated for lymphoreticular disorders and other hematologic malignancies. Because the phagocytic functions of neutrophils and mononuclear cells are the primary immune defense against invasive aspergillosis, Aspergillus is a common infectious cause of death in bone marrow transplant recipients. Outbreaks in transplant units have been epidemiologically linked to building demolition and construction, which releases fungal spores into the environment. There has been a significant increase in the incidence of invasive aspergillosis over the past few decades owing to the increasing numbers of patients undergoing transplantation, specifically for hematologic malignancies, as well an increase in the intensity of treatment regimens. Invasive aspergillosis in a patient without underlying disease is infrequent, and intensive investigation for a predisposing disorder should be undertaken.

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Clinical Manifestations

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Infection with Aspergillus can manifest as three distinct syndromes; two types of noninvasive aspergillosis; pulmonary aspergilloma and allergic bronchopulmonary aspergillosis (ABPA), as well as invasive aspergillosis, either locally invasive or disseminated disease.1

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Aspergilloma is the most common form of pulmonary aspergillosis2 and occurs when the fungus grows as a dense mass of hyphae and tissue debris within a preexistent pulmonary cavity caused by a concomitant pulmonary disease such as tuberculosis, lung abscess, or bronchiectasis. A patient with an aspergilloma may be asymptomatic and the lesion noted on incidental radiographic examination; however, there may be significant and life-threatening hemoptysis as a result of invasion of local bronchial blood vessels lining the cavity.

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ABPA is a hypersensitivity reaction to fungal antigens and is most commonly caused by A fumagatis. ABPA is seen in patients with chronic pulmonary disease such as asthma or cystic fibrosis. Some studies suggest that ABPA occurs in up to 15% of patients with cystic fibrosis3 and in 7% to 14% of patients with corticosteroid dependent asthma.4 Inhalation of fungal spores leads to hyphal colonization of the bronchopulmonary tree resulting in mucus plugging, ...

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