What is the pathophysiology of mold-related allergic fungal sinusitis (AFS)?

Updated: Dec 02, 2020
  • Author: Shih-Wen Huang, MD; Chief Editor: Harumi Jyonouchi, MD  more...
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Allergic Aspergillus sinusitis primarily occurs in patients with nasal polyps and mucoid impaction of the sinuses. The mucus typically contains eosinophils, Charcot-Leyden crystals (breakdown products of eosinophils), and hyphae of A fumigatus. AFS can also be induced with exposure to other fungi, including Bipolaris, Curvularia, Alternaria, Exserohilum, Helminthosporium, and Rhizopus species. This condition is relatively rare in the pediatric population and is a result of type 1, type 3 (immune complex), and type 4 (delayed type) hypersensitivity reactions. Manning et al reported on 6 patients aged 8-16 years who had findings typical to allergic Aspergillus sinusitis. [11]

A review of allergic fungal rhinitis and rhinosinusitis indicated epidemiologic studies have failed to demonstrate a direct relationship between fungal allergy and allergic rhinitis either via outdoor or indoor exposure. [5] The author indicated fungal allergy is clearly linked to a subset of chronic rhinosinusitis (CRS) known as allergic fungal rhinosinusitis (AFRS). The condition represents an intense allergic response against colonizing fungi that give rise to formation of allergic (eosinophilic) mucin, mucostasis, and sinus opacification.

A broader role for colonizing fungi has been postulated in CRS, owing to the demonstration of fungi in mucus in the vast majority of cases of CRS and in vitro studies that have demonstrated certain fungi, particularly Alternaria, modify an allergic response in patients with CRS that is independent of IgE. 

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