Nasal cavity, paranasal sinuses, nasopharynx

Infectious lesions

Allergic fungal sinusitis

Last author update: 1 March 2016
Last staff update: 12 August 2022

Copyright: 2003-2023,, Inc.

PubMed Search: Allergic fungal sinusitis [title] nasal

Margaret S. Brandwein-Weber, M.D.
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Cite this page: Sun J. Allergic fungal sinusitis. website. Accessed March 22nd, 2023.
Definition / general
  • Chronic allergic fungal sinusitis is an eosinophil mediated hypersensitivity reaction initiated by environmental fungi
Essential features
  • Characterized by thick allergic mucin (with degranulated eosinophils and Charcot crystals) and hyphal fragments on GMS stain
  • Also called allergic fungal rhinosinusitis
  • Multiple; nasal cavity or paranasal sinuses
  • Environmental causes
  • A. fumigatus, A. flavus or demateaceous fungi can trigger extreme eosinophil driven hypersensitivity to fungi in susceptible individuals
  • Allergic fungal sinusitis is a TH 2-like lymphocyte mediated response
Clinical features
  • Young adult with recurrent sinonasalpolyp, asthma, poor response to medical treatment
  • Peripheral eosinophilia, elevated IgE
Radiology description
  • CT: opacification of the nasal cavity and one or more paranasal sinuses
  • Erosion of bone (skull base and orbit) is seen in 20 - 60% of cases
Case reports
  • Complete endoscopic removal of the mucus and inflamed tissue followed by intranasal or systemic corticosteroids and possible maintenance therapy with fungal desensitization vaccines
Gross description
  • Edematous polypoid respiratory mucosa with thick, tenacious mucus similar to peanut butter or wet clay
Gross images

Contributed by Margie Brandwein-Gensler, M.D.

Allergic fungal rhinosinusitis

Microscopic (histologic) description
  • Diagnostic features: eosinophilic mucin with red and blue ripples (laminations composed of cellular debris, epithelium, polymorphonuclear cells, degranulated eosinophils and Charcot Leyden crystals)
  • Charcot Leyden crystals are pink/red refractive, and form long needle-like structures
  • Rare noninvasive fungal hyphae (often found only with GMS stain)
  • Schneiderian mucosa reveals thickened basement membrane with goblet cell hyperplasia, and numerous inflammatory cells with prominent eosinophils
  • Eosinophils may have degenerative changes of smudged, elongated or basophilic nuclei
Microscopic (histologic) images

Contributed by Kelly R. Magliocca, D.D.S., M.P.H.

Eosinophilic mucin associated with allergic fungal sinusitis

Charcot-Leyden crystals

Grocott-Gomori methenamine silver

Contributed by Margie Brandwein-Gensler, M.D.

Eosinophilic mucin

Fungal detection

Differential diagnosis
  • It is unclear if eosinophilic mucin rhinosinusitis (EMRS) is a distinct entity from allergic fungal sinusitis (AFS) because:
  • Fungal hyphae are not always detected in allergic mucin, although the sensitivity for fungal detection by the gold standard Gomori methanamine silver (GMS) stain is dramatically improved by trypsin predigestion, which speaks against EMRS as a distinct entity
  • On the other hand, aspirin sensitivity and bilateral sinus disease are more common types of eosinophilic mucin rhinosinusitis than allergic fungal sinusitis, consistent with the idea that ERMS represents a distinct clinical entity
  • Thus, this issue remains unresolved
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