Bronchopulmonary Aspergillosis

Bronchopulmonary aspergillosis is a lung condition that develops when the immune system overreacts to a common fungus found in soil and decaying plants, causing inflammation that can worsen breathing problems in people with asthma or cystic fibrosis.

Table of contents

• What Is Allergic Bronchopulmonary Aspergillosis?
• What Causes This Condition?
• Who Is Affected?
• Signs and Symptoms
• How Is It Diagnosed?
• Treatment and Management
• Possible Complications
• Reducing Your Risk

What Is Allergic Bronchopulmonary Aspergillosis?

Allergic bronchopulmonary aspergillosis, commonly called ABPA, is a lung infection caused by a hypersensitivity reaction to a fungus known as Aspergillus fumigatus^[1]. A hypersensitivity reaction means the immune system overreacts to something that is normally harmless. This fungus is found in soil and on decaying vegetation like compost heaps and fallen leaves^[2].

• Lungs
• Airways
• Bronchi
• Bronchioles

Although most people breathe in Aspergillus spores regularly without problems, certain individuals with weakened immune systems or existing lung conditions experience a severe allergic response^[2]. When the airways of patients with asthma or cystic fibrosis become colonized with Aspergillus, their immune system treats the fungus as a threat, triggering antibody and cell-mediated immune responses^[1].

ABPA most commonly affects people with asthma or cystic fibrosis^[2]. The thick mucus in the airways of these patients makes it difficult to clear the Aspergillus spores when inhaled^[1]. This immune reaction causes airway obstruction and can lead to permanent lung damage if left untreated^[2].

What Causes This Condition?

Aspergillus species are molds that are present everywhere in the environment, especially in organic matter. There are over 100 species worldwide, but most illness is caused by Aspergillus fumigatus, which is the most common cause of ABPA^[1]. Other species that can cause problems include Aspergillus niger, Aspergillus flavus, and Aspergillus clavatus^[1].

Aspergillus conidia are tiny spores measuring only 2 to 3 micrometers in diameter. Because of their small size, they easily reach deep into the lungs and deposit in the pulmonary alveoli, which are the tiny air sacs where oxygen exchange occurs^[1].

Genetic factors may play a role in who develops ABPA. Certain HLA-DR molecules (DR2, DR5, and possibly DR4 or DR7) contribute to susceptibility, while HLA-DQ2 contributes to resistance. A combination of these genetic markers may determine whether someone with cystic fibrosis or asthma will develop ABPA^[1].

Who Is Affected?

ABPA commonly appears in people during their third to fifth decade of life, though it is also seen in children. It usually affects people with severe asthma and patients with cystic fibrosis^[1].

Allergy to Aspergillus, as shown by a positive skin prick test to Aspergillus antigen, is present in almost 25% of people with asthma and 50% of cystic fibrosis patients. However, ABPA is not as common as the allergy itself. The prevalence of ABPA in asthma is about 13% and in cystic fibrosis is about 9%^[1].

Many people with ABPA also suffer from other allergic conditions such as atopic dermatitis (eczema), urticaria (hives), allergic rhinitis (hay fever), and sinusitis^[2].

Signs and Symptoms

If you have asthma, the first noticeable symptoms of ABPA are usually progressive worsening of your asthma symptoms such as wheezing and shortness of breath^[2]. The symptoms are similar to those of an asthma or cystic fibrosis exacerbation, but with additional signs^[1].

Common symptoms include:

• Wheezing
• Shortness of breath
• Cough that produces dirty-green or brown mucus plugs or brownish flecks
• Coughing up blood or bloody mucus
• Fever
• General weakness or feeling unwell (malaise)
• Loss of appetite
• Difficulty exercising
• Chest pain

These symptoms reflect airway obstruction, specifically wheezing and prolonged expiration, which are hard to distinguish from a regular asthma attack^[1].

How Is It Diagnosed?

Diagnosis for ABPA is determined by health history, imaging tests, allergy skin testing, and blood tests^[2]. Your doctor will suspect ABPA if you have asthma or cystic fibrosis with frequent exacerbations, infiltrates on chest x-ray that move or don’t resolve, evidence of bronchiectasis (abnormal widening of the airways), positive sputum cultures for Aspergillus fumigatus, or notable increase in certain white blood cells called eosinophils^[1].

The diagnostic process typically includes:

Imaging Tests: Chest X-rays or CT scans can reveal a fungal mass or show signs of ABPA. High-resolution CT scans are particularly useful for detecting bronchiectasis^[2].

Skin Testing: A small amount of Aspergillus antigen is injected into the skin of your forearm. If your blood has antibodies to the mold, you’ll develop a hard, red bump at the injection site^[2].

Blood Tests: These look for high levels of certain antibodies, particularly IgE (immunoglobulin E), which indicates an allergic response. Blood tests also measure circulating precipitins and Aspergillus fumigatus-specific antibodies^[2].

Sputum Tests: A sample of mucus you’ve coughed up is stained with dye and checked for the presence of Aspergillus fibers. The sample is then placed in a culture that encourages the mold to grow, which helps confirm the diagnosis^[1].

Blood Eosinophil Count: An elevated count of these white blood cells can support the diagnosis^[1].

Treatment and Management

The fungus that causes ABPA is difficult to avoid, so medication is typically prescribed to manage the condition^[2]. Treatment typically includes oral steroids for several weeks, sometimes in combination with an antifungal medication^[6].

Corticosteroids: These are the main treatment for ABPA and work by reducing inflammation. Asthma medications such as oral corticosteroids open the airways and make it easier to cough and clear out the fungus^[2]. It’s important to understand that inhaled steroids are not effective for ABPA; oral steroids are required^[11]. The prescription depends on the individual and the severity of ABPA. Some people take the medication when they have symptoms, while others with more severe cases may require daily corticosteroid therapy^[2].

Antifungal Medications: An oral antifungal such as itraconazole may be recommended to reduce the fungal burden^[2]. Adding oral itraconazole to steroids in patients with recurrent or chronic ABPA may be helpful, allowing for more rapid resolution of infiltrates and symptoms, and facilitating steroid tapering or lowering the needed maintenance corticosteroid dosage^[11]. It’s important to note that in cystic fibrosis patients with ABPA, the combined use of itraconazole and inhaled corticosteroids may increase the risk of adrenal insufficiency^[11].

Biologic Medications: Newer treatments including biologics such as omalizumab (Xolair) and dupilumab are being clinically evaluated in patients with ABPA. Case reports have described beneficial use of the anti-IgE monoclonal antibody omalizumab in patients with ABPA^[11].

Mucus Clearance: Mucus clearance physiotherapy can help remove secretions from the airways^[6].

If you are diagnosed with ABPA, you should be followed closely by your physician to prevent or minimize damage to your lungs^[2]. The goal is to treat the disease early to protect the lung from damage caused by long-standing inflammation^[13].

Possible Complications

Over time, if ABPA is not properly managed, the immune reactions combined with direct toxic effects of the fungus can lead to airway damage with dilation and, ultimately, bronchiectasis and fibrosis (scarring) of the lungs^[1].

Some complications of untreated ABPA include:

Haemoptysis: The irritated and inflamed airways can bleed, and blood-stained phlegm is coughed up^[19].

Bronchiectasis: Recurring bouts of inflammation eventually damage the bronchiolar walls, causing abnormal widening of the bronchial tubes. This can result in worse lung function and increased risk of infection^[6].

Atelectasis: This involves varying degrees of lung tissue collapse^[19].

Respiratory Failure: The airways become obstructed, or a severe asthma attack squeezes the airways closed^[19].

Pulmonary Fibrosis: Long-term infection can cause lung tissue to thicken and scar, making it more difficult for the lung to exchange gases with the blood supply^[13].

Pulmonary Hypertension: High blood pressure in the arteries of the lungs^[13].

While ABPA cannot be cured, it can go into remission. In remission, the person with ABPA has no symptoms, has asthma under control, and has no new suspicious findings on X-ray or any increases in IgE levels for at least 6 months^[13].

Reducing Your Risk

Aspergillus spores are common in indoor and outdoor environments, making it difficult to avoid breathing them in^[16]. However, there are some ways to lower your chances of developing problems:

Avoid Dusty Areas: Try to avoid areas like construction or excavation sites. If you cannot avoid these areas, wear an N95 respirator^[16].

Limit Contact with Soil and Dust: Avoid activities involving close contact with soil or dust. When doing outdoor activities, wear shoes, pants, and long sleeves^[16].

Environmental Control: Reduce exposure to mold and dust in your home. This includes controlling dampness and addressing any mold problems^[6].

Good Hygiene: Clean skin injuries well with soap and water to avoid skin infection^[16].

Stick to Your Treatment Plan: Attend regular check-ups, monitor symptoms like coughing, mucus, breathlessness or chest pain, and practice good airway clearance techniques^[18].

It’s important to note that although these actions are recommended, they haven’t been proven to prevent ABPA^[16]. Some events can cause disease exacerbation even with preventive measures^[13].