This disorder refers to symptomatic infection with organisms of the Aspergillus species. Aspergillus is a dimorphic fungus which is ubiquitous and is commonly found in stored hay or grain, decaying vegetation, soil, dung and compost piles. Most cases of aspergillosis are secondary to infection with A. fumigatus and, less commonly, A. flavus. Other Aspergillus species include A. niger, A. sydowi, A. terreus, A. ustus, A. versicolor, A. amstelodami, A. oryzae, A. restrictus, A. candidus, A. nidulans, A. carneus, A. caesiellus, A. clavatus, and A. avenaceus. Infection occurs when airborne conidia (spores) are inhaled and enter the alveoli. Other less common sites of infection include the nose, paranasal sinuses, skin, cardiac valves (endocarditis associated with intravenous drug abuse), central nervous system, and eye.
There are three distinct syndromes that occur with pulmonary infection to include aspergilloma, allergic bronchopulmonary aspergillosis (ABPA), and invasive aspergillosis. All three disorders have various manifestations, are diagnosed differently and require differing therapies.
An aspergilloma refers to a fungus ball that results when Aspergillus organisms infect a preexistent pulmonary cavity or ectatic bronchus. Therefore, this organism causes secondary infections associated with such disorders as tuberculosis, sarcoidosis, coccidioidomycosis, histoplasmosis, emphysematous bullae, bronchiectatic cavities, and pneumoconiosis. Most patients present with either an asymptomatic chest radiograph cavitary lesion or hemoptysis (secondary to anticoagulants produced by the infecting organism). The differential diagnosis includes other secondary fungal infections, disintegrating echinococcal cysts, intracavitary blood clot, necrotic tissue within a cavitating carcinoma, or lung abscess. The diagnosis is usually established by typical chest radiographic abnormalities, the recovery of Aspergillus in multiple sputum samples and the presence of serum precipitins (Aspergillus complement fixation titers). Therapy is controversial. When associated with severe symptoms, such as life-threatening hemoptysis, surgical resection is the treatment of choice. Many asymptomatic aspergillomas require no therapy. The role of intracavitary or systemic antifungal agents is controversial.
When there is a hypersensitivity response to Aspergillus infection, the patient suffers from allergic bronchopulmonary aspergillosis (ABPA). Patients afflicted with this disorder are usually persons who suffer from asthma. The differential diagnosis includes asthma, pulmonary eosinophilic syndromes and helminthic lung disease. The major diagnostic criteria for ABPA are as follows: episodic bronchial obstruction, peripheral eosinophilia, a positive immediate skin test reactivity to Aspergillus, a significantly elevated serum IgE, a positive serum Aspergillus complement fixation titer, pulmonary infiltrates and central bronchiectasis noted on chest radiograph or chest CT scan. Minor criteria include the following: sputum cultures positive for Aspergillus, a late skin test reactivity to Aspergillus and a history of expectorating brown mucus plugs. One approach to the diagnosis of ABPA is to perform skin test sensitivity to Aspergillus in any patient suspected of infection (persons with asthma, pulmonary infiltrates or central bronchiectasis on CXR and sputum contaminated with Aspergillus). If the skin test is positive, the levels of serum IgE and Aspergillus complement fixation titers should be checked. Therapy entails corticosteroids with bronchodilators and cromolyn sodium.
The third form of pulmonary disease is invasive aspergillosis, which usually manifests as a diffuse, patchy necrotizing bronchopneumonia. This form of infection may be seen in nonimmunosuppressed patients, but this is mostly a disease of the immunocompromised. It is most commonly associated with acute leukemia; however, patients suffering from AIDS (usually with CD4 counts less than 50 mm3), lymphoma, or renal transplant recipients may also be affected. This disease usually manifests as dyspnea, tachypnea, a nonproductive cough and pleuritic chest pain. The diagnosis is established by transbronchial biopsy or positive blood cultures. Examination of the sputum for Aspergillus or the serum for Aspergillus complement fixation titers is generally unrewarding. This form of infection is generally fatal, and therapy with amphotericin B or other antifungals usually has little effect on the prognosis.