There are a number of recognised pulmonary forms, the number depending on the author 1,3-4 . Each form has specific clinical and radiological features and are discussed in separate articles:
- aspergilloma (saprophytic/noninvasive aspergillosis): the most common form seen radiographically
- allergic bronchopulmonary aspergillosis (ABPA)
- invasive aspergillosis
- obstructive bronchopulmonary aspergillosis
The remainder of this article discusses general concepts pertaining to pulmonary aspergillosis.
The various species of Aspergillus are ubiquitous and usually do not cause any human pathology provided the lungs are structurally normal and the host immunity is intact. If either of these is abnormal, then there is the possibility that this otherwise benign fungus may cause pathology.
Role of immunity in aspergillosis
In a patient with normal immunity, Aspergillus is unable to cause pulmonary pathology. Altered immunity, both heightened (hypersensitivity) or reduced (immunocompromised) predisposes to Aspergillus related lung disease.
Patients with hypersensitivity may develop allergic bronchopulmonary aspergillosis (ABPA), whereas immunocompromised patients can develop semi-invasive or invasive aspergillosis depending on the degree to which their immune system is depressed.
Role of pulmonary structure in aspergillosis
Aspergillus can colonise pre-existing pulmonary cavities, particularly those left behind by pulmonary tuberculosis. In this setting the fungus grows and as it is free to move within the cavity, typically takes on a spherical shape, and is known as an aspergilloma. Other cavities that can predispose to aspergilloma include bullae which may be secondary to emphysema.
- 1. Franquet T, Müller NL, Giménez A et-al. Spectrum of pulmonary aspergillosis: histologic, clinical, and radiologic findings. Radiographics. 21 (4): 825-37. Radiographics (full text) - Pubmed citation
- 2. Zmeili OS, Soubani AO. Pulmonary aspergillosis: a clinical update. QJM. 2007;100 (6): 317-34. doi:10.1093/qjmed/hcm035 - Pubmed citation
- 3. Collins J, Stern EJ. Chest radiology, the essentials. Lippincott Williams & Wilkins. (2007) ISBN:0781763142. Read it at Google Books - Find it at Amazon
- 4. Müller NL, Franquet T, Lee KS et-al. Imaging of pulmonary infections. Lippincott Williams & Wilkins. (2007) ISBN:078177232X. Read it at Google Books - Find it at Amazon
- 5. Zander DS. Allergic bronchopulmonary aspergillosis: an overview. Arch. Pathol. Lab. Med. 2005;129 (7): 924-8. doi:10.1043/1543-2165(2005)129[924:ABAAO]2.0.CO;2 - Pubmed citation