|Classification and external resources|
Aspergillomas complicating tuberculosis: multiple aspergillomas within large cavitary lesions of tuberculous origin.
An aspergilloma, also known as a mycetoma or fungus ball, is a clump of fungus which exists in a body cavity such as the lung. It is associated with the Aspergillus species, but Zygomycota and Fusarium may also form similar structures.
The most common place affected by aspergillomas is the lung. Aspergillus fumigatus, the most common species, is typically inhaled as small (2 to 3 micrometer) spores which do not affect people without underlying lung or immune system disease. However, people who have pre-existing lung problems, especially the cavities typically caused by tuberculosis, are at risk for developing aspergillomata. The fungus settles in a cavity and is able to grow free from interference because the immune system is unable to penetrate into the cavity. As the fungus multiplies, it forms a ball, which incorporates dead tissue from the surrounding lung, mucus, and other debris.
Typically, individuals who are affected by aspergillomata do not have symptoms related to the infection. People often co-exist for decades with aspergillomata prior to incidental diagnosis, typically by X-ray or computed tomography. However, a small percentage of aspergillomata invade into the wall of the cavity and can result in bleeding. Thus, the most common symptom of associated with aspergillomata is coughing up blood (hemoptysis). Although this can occasionally be life-threatening, the amount of blood produced is usually inconsequential.
Aspergillomata can form in other body cavities. They can form abscesses in the brain, usually in people who are immunocompromised. They can also form within the different sinuses in the face, within the kidneys and urinary system, the ear canal, and on the heart valves.
Most cases of aspergilloma do not require treatment. Treatment of diseases which increase the risk of aspergilloma, such as tuberculosis, may help prevent their formation. In cases complicated by severe hemoptysis, surgery may be required to remove the aspergilloma and stop the bleeding. There has been interest in treatment with antifungal medications, such as itraconazole, but as of 2005, none has been shown to eradicate aspergillomae.
While fungus can grow within a pre-existing lung cavity as a rounded mass of hyphae, there is another, probably more common cause of "fungus ball." Although fungi, especially Aspergillus, fail to grow in healthy humans, significant growth may occur during periods of diminished resistance including very low white blood cell counts. Within the lungs of immunocompromised individuals the fungal hyphae spread out as a spherical growth. With restoration of normal defense mechanisms, white blood cells are attracted to the edge of the spherical fungal growth where they lyse, releasing tissue-digesting enzymes as a normal function. A sphere of infected lung is thus cleaved from the adjacent lung. This sphere flops around in the resulting cavity and is recognized on x-ray as a fungus ball but is really a "lung ball". This process is benficial as a potentially serious invasive fungal infection is converted into surface colonization. Although the fungus is inactivated in the process, surgeons may choose to operate to reduce the possibility of bleeding. Microscopic examination of surgically removed recently-formed fungus balls clearly show a sphere of dead lung containing fungal hyphae. Microscopic examination of older lesions reveal mummified tissue which may reveal faint residual lung or hyphal structures.
- "aspergilloma" at Dorland's Medical Dictionary
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- Aspergillus organization: diagnosis, treatment, cases, images, educational video