Allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is a specific allergic reaction to Aspergillus species observed in individuals with asthma and cystic fibrosis.

AspeOverview

Allergic bronchopulmonary aspergillosis is a disorder caused by the body’s allergic reaction to fungal infection, in this case, Aspergillus fumigatus.  The disease develops when a person inhales the spores of the fungi. Moreover, this occurs almost exclusively in individuals suffering from asthma or cystic fibrosis. Recurrent episodes of Aspergillus infection lead to chronic inflammation and result in bronchiectasis formation and progressive fibrosis of the lungs. Typically, disease manifests with shortness of breath,  coughing and wheezing – these symptoms are characteristic for asthma and cystic fibrosis, but fungal infection induces exacerbation of the comorbidities.

Causes

Aspergillus species are the saprophytic fungus known also as molds. Aspergillus fumigatus, Aspergillus niger, Aspergillus flavus and Aspergillus clavatus are the most common molds observed in humans. The fungi are transmitted when a person inhales spores and cause allergic bronchopulmonary aspergillosis (ABPA), chronic necrotizing Aspergillus pneumonia (or chronic necrotizing pulmonary aspergillosis [CNPA]), aspergilloma or invasive aspergillosis. Furthermore, in individuals who have a very weak immune system (for example, those who receive immunosuppressive drugs, have AIDS or other immunodeficiencies) may develop a severe disease affecting the heart, kidney, liver, spleen or even central nervous system.

As for allergic bronchopulmonary aspergillosis, it develops as a result of hypersensitivity reaction in individuals with asthma and cystic fibrosis to Aspergillus fumigatus that colonizes the respiratory tract.  It was proposed that susceptibility of individuals with asthma and cystic fibrosis is predisposed by the increased activity of A. fumigatus specific T-helpers type 2 and abnormal immune response to this fungus with the production of specific IgE.

Risk factors

The abnormal immune response that trigger development of allergic bronchopulmonary aspergillosis usually occurs in individuals that have:

  • Asthma;
  • Cystic fibrosis;
  • History of other atopic diseases including allergic rhinitis, atopic dermatitis;

Symptoms

Allergic bronchopulmonary aspergillosis manifests as exacerbation of asthma/cystic fibrosis and the following symptoms are typical:

  • Shortness of breath;
  • Productive cough with dirty-green or brown mucus plugs that form bronchial casts or bloody sputum (hemoptysis);
  • Wheezing;
  • Fever;
  • General malaise;
  • Weight loss;

Stages

The disease has several stages, though they are not consistent.

Stage I (acute)

At this stage of the disease, acute fungal infection leads to the formation of pulmonary infiltrates and causes fever, productive cough and wheezing. Blood eosinophilia, elevated serum IgE are detected.

Stage II (remission)

The symptoms are absent for longer than 6 months. Additionally, blood eosinophilia subsides.

Stage III (relapse/exacerbation)

As the infection reactivates individual experiences disease exacerbation.

Stage IV (refractory)

Recurrent infections require retreatment with corticosteroids, therefore, eventually, long-term administration of steroids is necessary to keep asthma/cystic fibrosis under control.

Stage V (fibrosis)

There is diffuse fibrosis of the lungs and multiple bronchiectases leading to severe shortness of breath and bronchospasm that cannot be reversed with treatment.

Diagnosis

Diagnosis of ABPA requires the next investigations:

  • Pulmonary infiltrates and bronchiectasis may be seen on chest X-ray. Chest CT may be required to estimate lung involvement;
  • Skin prick testing with Aspergillus antigen are used to confirm sensitization to A.fumigatus;
  • Aspergillus species may be found in the sputum culture;
  • Levels of serum IgE are increased (>1000 U/mL) and specific IgE to A.fumigatus may be detected in the blood;
  • Blood eosinophilia of >1000 cells/mm3;

Treatment

Allergic bronchopulmonary aspergillosis requires the administration of antifungal medications such as itraconazole or voriconazole.

However, as solely infection treatment is not enough administration of corticosteroids to suppress abnormal immune reaction are necessary. Oral steroids are the mainstay of exacerbation treatment. Inhaled corticosteroids are used to provide symptomatic relief and reduce bronchoconstriction along with β-agonists and anticholinergics.

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