Aspergillosis - Pulmonary
Aspergillus, a hyaline mold, is found ubiquitously worldwide in decaying vegetation, soil, water, food, and plants. Inhalation of Aspergillus conidia into the lungs is the most common mode of acquisition. The varied pulmonary manifestations of infection depend to a large degree on the immune status of the host. They range from colonization leading to tracheobronchitis or a fungus ball to invasive disease in immunocompromised patients. There also can be an allergic response as with allergic bronchopulmonary aspergillosis (ABPA).
Aspergillus tracheobronchitis, which occurs in lung transplant recipients, can be asymptomatic but may cause fever, cough, wheezing, and hemoptysis.
An aspergilloma, or fungus ball, is a solid clump of mold growing in a pre-existing pulmonary cavity. This is most common in an immunocompetent host. It presents clinically with cough and hemoptysis.
ABPA syndrome is characterized by transient pulmonary infiltrates, and exacerbation of dyspnea, wheezing, and cough in chronic asthmatics and patients with cystic fibrosis.
Patients with prolonged and profound neutropenia (absolute neutrophil count <100/mm3), those undergoing hematopoietic stem cell transplantation (HSCT), patients on chronic high dose corticosteroids, patients with chronic granulomatous disease, solid organ transplant recipients (especially lung), and those on newer immunosuppressives such as TNF-alpha antagonists or T-cell ablative agents (alemtuzumab, antithymocyte globulins) are at risk for invasive disease. This most commonly begins in the lung, and dissemination can occur by hematogenous route or as a result of local extension. Dissemination can lead to central nervous system, liver, spleen, heart, bone, and skin involvement. Invasive pulmonary aspergillosis often presents with asymptomatic fever and incidental radiographic findings, but can also present with dry cough, dyspnea, pleuritic chest pain, and fever. These symptoms can resemble those of pulmonary embolism, reflecting the angio-invasive nature of the disease.
A locally invasive or semi-invasive form of the disease that lacks vascular invasion or distant dissemination is also recognized. This is an indolent process that develops over months or years, hence its other name, chronic necrotizing aspergillosis.
Cutaneous aspergillosis begins as red papules that form pustules. These pustules ulcerate and leave a central eschar evocative of the diagnosis.
B44.9 – Aspergillosis, unspecified
65553006 – Aspergillosis
- Other invasive molds like Fusarium and Scedosporium are impossible to distinguish based on morphology, and diagnosis requires a positive culture.
- The molds belonging to the Mucorales order (especially Rhizopus), which cause mucormycosis, may present with similar clinical syndromes but are usually distinguishable from Aspergillus based on morphology. Mucorales fungi are broad, nonseptate hyphae with branches at right angles.
- In immunocompromised patients with pulmonary nodules, there are many infectious and noninfectious etiologies that are possible (an infectious diseases consultation is recommended). Some organisms to consider include Nocardia species, mycobacterial species, Legionella species, cryptococcal infection, and the endemic fungi. In some cases, Pneumocystis jirovecii and even viral pathogens can present with nodular lung disease. Septic emboli are possible (especially in patients who may have indwelling central venous catheters). Noninfectious causes of nodular lung disease including malignancy should also be considered.