The Aspergillus fungus causes aspergillosis pulmonary infections. Although there are more than 100 Aspergillus species, most human illnesses are caused by Aspergillus fumigatus and Aspergillus niger and, less frequently, Aspergillus flavus and Aspergillus clavatus.
The fungus that causes the infection is commonly found on dead leaves, stored grain, compost piles, and decaying vegetation. People are commonly exposed to the fungus, but it usually only causes infections in individuals who have weakened immune systems, such as HIV/AIDS patients.
The fungal spores are transmitted to humans when they are inhaled. Therefore, the infection primarily affects the lungs. However, if the patient is severely immunocompromised (as in HIV/AIDS or cancer patients), the infection may spread to other organs. In such cases, the infection may cause endophthalmitis (inflammation of the eye that is a medical emergency), endocarditis (infection of the lining of the heart), and abscesses in the heart muscle, kidney, liver, spleen, soft tissue, and bone.
There are four main types of aspergillosis: allergic bronchopulmonary aspergillosis (ABPA), chronic necrotizing Aspergillus pneumonia (CNAP), aspergilloma, and invasive aspergillosis.
According to the U.S. Centers for Disease Control and Prevention (CDC), aspergillosis is not considered an AIDS-defining illness (illness that indicates that the patient's condition has progressed to AIDS).
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types of aspergillosis
Allergic bronchopulmonary aspergillosis (ABPA): Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitive reaction to A. fumigatus, which causes inflammation of the airways and air sacs of the lungs. This reaction usually occurs along with asthma and cystic fibrosis (genetic disorder of the mucus in the lungs that causes breathing problems). Allergic fungal sinusitis (inflammation of the sinuses caused by fungal exposure) may also occur. ABPA may worsen asthma symptoms. Repeated episodes of ABPA may cause widespread bronchiectasis (dilation of airway passages) and cause chronic fibrotic lung disease.
About 25% of asthmatics and 50% of patients who have cystic fibrosis are allergic to Aspergillus.However, only a few people develop ABPA. According to surveys and an ABPA registry, only 0.25-0.8% of asthmatics and about seven percent of patients with cystic fibrosis are estimated to have ABPA. The incidence of ABPA in people with asthma who are dependent on steroid inhalers or have associated central bronchiectasis is estimated to be between 7-10%.
pneumonia (CNAP): Chronic necrotizing Aspergillus pneumonia (CNAP) is a rare condition that usually occurs in patients who have weakened immune systems. This condition is frequently associated with underlying lung disease, alcoholism, or long-term corticosteroid therapy. Since the condition usually is not discovered until an autopsy is conducted after the patient has died, the frequency of CNAP may be underestimated. Also, because CNAP is rare, it often remains unrecognized for weeks or months, allowing the fungus spores to multiply in the lungs. CNAP has a reported mortality rate of 10-40%. However, rates as high as 100% have been noted because it often remains undiagnosed for such a long time.
Aspergilloma: An aspergilloma is a fungus ball (mycetoma) that develops in a pre-existing lung cavity (abnormal space between the membranes that line the lungs). Underlying causes of the cavitary disease may include tuberculosis or other necrotizing infection, sarcoidosis (inflammation of the lymph nodes, liver, lungs, and spleen), cystic fibrosis, and emphysematous bullae (blisters under the skin). According to one survey of patients who had cavitary lung disease due to tuberculosis, 17% developed aspergilloma. The ball of fungus may move inside the cavity, but it does not enter the cavity wall. Aspergilloma may cause hemoptysis (blood in the sputum), which may be severe and life threatening.
Invasive aspergillosis: Invasive aspergillosis is a rapidly progressive, often fatal infection that occurs in patients who have extremely weakened immune systems. Patients who have undergone bone marrow transplants or solid organ transplants, those who are neutropenic (low levels of white blood cells called neutrophils), and patients with advanced AIDS or chronic granulomatous disease (inherited disorder that impairs phagocytic cells that normally kill bacteria that enters the body) are susceptible to invasive aspergillosis. The fungus spores invade the blood vessels and infiltrate the membranes that surround the lungs. The infection may spread to other organs, especially the central nervous system (CNS).
Invasive aspergillosis is estimated to occur in 5-13% of bone marrow transplant recipients, 5-25% of patients who have received heart or lung transplants, and 10-20% of patients receiving intensive chemotherapy for leukemia. Although there have been reports of invasive aspergillosis in patients who have healthy immune systems, it is extremely rare. Invasive aspergillosis is associated with a high rate of mortality (30-95%).