There are challenges involved in long-term therapy with corticosteroids—which can induce severe immune dysfunction when used chronically, as well as metabolic disorders—and approaches have been developed to manage ABPA alongside potential adverse effects from corticosteroids.The most commonly described technique, known as sparing, involves using an antifungal agent to clear spores from airways adjacent to corticosteroid therapy. The antifungal aspect aims to reduce fungal causes of bronchial inflammation, whilst also minimising the dose of corticosteroid required to reduce the immune systems input to disease progression. The strongest evidence (double-blinded, randomized, placebo-controlled trials) is for itraconazole twice daily for four months, which resulted in significant clinical improvement compared to placebo, and was mirrored in CF patients. Using itraconazole appears to outweigh the risk from long-term and high-dose prednisone. Newer triazole drugs—such as posaconazole or voriconazole—have not yet been studied in-depth through clinical trials in this context.Whilst the benefits of using corticosteroids in the short term are notable, and improve quality of life scores, there are cases of ABPA converting to invasive aspergillosis whilst undergoing corticosteroid treatment. Furthermore, in concurrent use with itraconazole, there is potential for drug interaction and the induction of Cushing syndrome in rare instances. Metabolic disorders, such as diabetes mellitus and osteoporosis, can also be induced.In order to mitigate these risks, corticosteroid doses are decreased biweekly assuming no further progression of disease after each reduction. When no exacerbations from the disease are seen within three months after discontinuing corticosteroids, the patient is considered to be in complete remission.
These cytokines up-regulate mast cell degranulation, exacerbating respiratory decline.Aspergillus also utilises a number of factors to continue evading host responses, notably the use of proteolytic enzymes that interrupt IgG antibodies aimed towards it. Another important feature is its ability to interact and integrate with epithelial surfaces, which results in massive pro-inflammatory counter-response by the immune system involving IL-6, IL-8 and MCP-1 (a CCL2 receptor ligand). Proteases released by both the fungus and neutrophils induce further injury to the respiratory epithelium, leading to initiation of repair mechanisms (such as an influx of serum and extracellular matrix (ECM) proteins) at the site of infection. Aspergillus spores and hyphae can interact with ECM proteins, and it is hypothesised that this process facilitates the binding of spores to damaged respiratory sites.As concentrations of Aspergillus proteases increase, the immunological effect switches from pro-inflammatory to inhibitory, and further reduces phagocytic ability to clear Aspergillus. Ultimately, repeated acute episodes lead to wider scale damage of pulmonary structures (parenchyma) and function via irreversible lung remodelling. Left untreated, this manifests as progressive bronchiectasis and pulmonary fibrosis that is often seen in the upper lobes, and can give rise to a similar radiological appearance to that produced by tuberculosis. Diagnosis
The exact criteria for the diagnosis of ABPA are not yet universally agreed upon, though working groups have proposed specific guidelines.