Nasal cavity, paranasal sinuses, nasopharynx
Infectious lesions
Allergic fungal sinusitis

Topic Completed: 1 March 2016

Minor changes: 2 March 2020

Copyright: 2003-2020,, Inc.

PubMed Search: Allergic fungal sinusitis [title] nasal

Jihong Sun, M.D.
Margaret S. Brandwein-Weber, M.D.
Page views in 2019: 5,816
Page views in 2020 to date: 3,023
Cite this page: Sun J. Allergic fungal sinusitis. website. Accessed September 28th, 2020.
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

Images hosted on PathOut server:

Contributed by Margie Brandwein-Gensler, M.D.

Image hosted on other servers:
Missing Image

Allergic fungal
rhinosinusitis, thick mucin,
often described as similar
to peanut butter or wet clay

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

Images hosted on PathOut server:

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.

Image hosted on other servers:

Allergic mucin

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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