Aspergillus is a family of mold with over 100 species worldwide. It is a common fungus found within indoor environments and a cause of a type of fungal infection called allergic bronchopulmonary aspergillosis (ABPA).
ABPA is a combination of allergy plus lung infection. After Aspergillus spores invade the lung tissue, it can grow in a process known as germination. The invading mold triggers a hypersensitivity reaction and can cause:
- Bronchospasm: tightness in the lungs
- Pulmonary infiltrates: inflammation in the lungs
- Eosinophilia: a rise in an allergic-related immune cell, the eosinophil, within the blood
- Immune response: a rise in IgG or IgE antibodies.
Four main species cause this dangerous medical condition:
- Aspergillus fumigatus,
- Aspergillus niger,
- Aspergillus flavus,
- and Aspergillus clavatus.
Of these species, Aspergillus fumigatusis the leading cause of ABPA. One reason for its ability to infect is the small size of its spores. At 2 to 3 micrometers, the spores can easily reach the deepest part of the lung with breathing.
Host factors matter as well. Exposure to Aspergillus is common, but only the vulnerable develop the condition. The susceptibility arises from HLA susceptibility, along with three medical conditions—asthma, cystic fibrosis, and a weak immune system.
Tests for Aspergillosis
No test for ABPA is 100% accurate. This condition is diagnosed based on complex pattern recognition involving the clinical features, radiographic findings, and immune testing. Tests include:
- Skin prick with Aspergillus antigen This test is positive in up to 25% of patients with asthma and 50% suffering from cystic fibrosis. By itself a positive skin prick test is not diagnostic of ABPA as only about 9-13% of patients with either condition will also develop ABPA.
- High total IgE IgE is an antibody produced by the immune system. It can be measured through a blood test to assess for a range of allergic conditions, including asthma, ABPA, and other immune-related disorders.
- High IgE to Aspergillus fumigatus This body test demonstrates an allergic-type response to this form of Aspergillus.
- High eosinophilsEosinophils are a type of white blood cell that can be measured in a standard blood test. They help the body defend against parasites, allergens, and other outside organisms.
There are radiographic tests to assess for ABPA.
- Chest x-rays are the most common and can show lung inflammation, as well as bronchiectasis, a swelling of the bronchi airways within the lungs.
- High-resolution CT scan of the chestis the best method for assessing bronchiectasis, nodule growths and other imaging irregularities. The absence of abnormalities on HRCT does not necessarily exclude ABPA in a patient who has clinical and blood markers of this condition.
As an inflammatory disorder caused by infection, the treatment of ABPA focuses on eliminating Aspergillus growth, along with controlling the extent of inflammation. Treatment is intended to control symptoms, prevent flares, and preserve lung health.
There are four categories of drugs used in the standard treatment of ABPA:
- Anti-inflammatory drugs such as corticosteroids
- Anti-fungal drugs, usually itraconazole
- Anti-IgE therapy that reduces allergic responses
- Antibiotics to prevent bacterial infections from adding onto the lung infection.
With appropriate treatment started early enough, patients who are not too sick can control symptoms and keep the condition in remission. The duration and type of treatment varies based on the stage of the condition.
SISODIA JITENDRA, Bajaj T. Allergic Bronchopulmonary Aspergillosis. [Updated 2023 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
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