Aspergillus fumigatus is a fungus of the genus Aspergillus, and is one of the most common Aspergillus species to cause disease in individuals with an immunodeficiency. A. fumigatus, a saprotroph widespread in nature, is typically found in soil and decaying organic matter. Colonies of the fungus produce thousands of small conidia (2-3 μm) that readily become airborne. The fungus is capable of growth at temperatures up to 50 °C, with conidia surviving at 70 °C. Humans are continuously in contact with these asexual spores and it is estimated that an individual inhales several hundred conidia each day; typically these are quickly eliminated by the immune syste Aspergillosis develops mainly in individuals who are immunocompromised, either from disease or from immunosuppressive drugs, and is a leading cause of death in acute leukemia and hematopoietic stem cell transplantation.The term aspergillosis comprises a number of different diseases caused by fungi of the genus Aspergillus. The most common forms are allergic bronchopulmonary aspergillosis (ABPA), pulmonary aspergilloma and invasive aspergillosis (IA).Allergic bronchopulmonary aspergillosis is characterized by an exaggerated response of the immune system to Aspergillus species. It occurs in patients suffering from asthma or cystic fibrosis. Clinically, ABPA manifests as a bronchial asthma with transient pulmonary infiltrates that may proceed to proximal bronchiectasis and lung fibrosis.Aspergilloma, commonly referred to as 'fungus ball,' occurs in preexisting pulmonary cavities that were caused by tuberculosis, sarcoidosis, or other bullous lung disorders. The fungus settles in a cavity and grows until it forms a compact sphere, which incorporates dead tissue from the surrounding lung, mucus, and other debris. Patients are usually asymptomatic and often co-exist for decades with aspergillomae prior to incidental diagnosis. However, it may cause hemoptysis.Invasive aspergillosis is a rapidly progressive, often fatal disease, targeting severely immunocompromised patients, including those with hematological malignancies such as leukemia, those who have received solid organ or hematopoietic stem cell transplants, and individuals with chronic granulomatous disease or advanced AIDS. IA is characterized by invasion of blood vessels, resulting in multifocal infiltrates. Dissemination to other organs, particularly the central nervous system, may occur.
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