What causes allergic fungal sinusitis (AFS)?

Updated: Mar 16, 2018
  • Author: John E McClay, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

Most rhinologists believe that allergic fungal sinusitis (AFS) is an allergic reaction to fungi, in which fungal debris, allergic mucin, and nasal polyposes are formed in the nasal cavity and paranasal sinuses. The causative fungi in allergic fungal sinusitis (AFS) are usually dematiaceous fungi, consisting of the genera Bipolaris, Curvularia, Exserohilum, Alternaria, Drechslera, Helminthosporium, and Fusarium, with a small component of allergic fungal sinusitis (AFS) caused by Aspergillus. In a 1996 review of English literature performed by Manning, 263 cases of allergic fungal sinusitis (AFS) were identified, of which 168 cases yielded positive fungal cultures. Of these 168 positive cultures, 87% were from the dematiaceous genera, while only 13% yielded Aspergillus.

The largest reported single institutional experience to date is at the UT Southwestern Medical Center in Dallas, Texas. The fungi recovered from the paranasal sinuses in that evaluation by the author and colleagues revealed that Bipolaris, followed by Curvularia, is the most common pathogen present, seen with similar incidence in adults and children, see Table 1 below. Most large reviews agree, indicating that Bipolaris and Curvularia species are the most common fungi recovered.

When geographic location is specifically reviewed, the further west and inland the series, the more likely that Bipolaris species dominated the fungi recovered. When the series was performed in the Southeast, Curvularia species were more likely to be recovered. Interestingly, in the UT Southwestern experience, Aspergillus was recovered in 13% of adults but in no children. A report from India found only Aspergillus species identified in all 11 patients with allergic fungal sinusitis (AFS) in whom fungus was recovered.

Table 1. Causative Fungus Identified at UT Southwestern Medical Center (Open Table in a new window)

Fungus

Children (n=44)

Adults (n=107)

Bipolaris

21 (66%, 21/32)

40 (57%, 40/70)

Curvularia

7 (22%, 7/32)

12 (17%, 12/70)

Exserohilum

2

2

Alternaria

1

3

Aspergillus (niger/flavus)

0

9 (13%)

Acremonium

0

1

Chrysosporium

0

1

Helminthosporium

0

1

No Growth

2

21

No Data

12

16

Combination

1 Bipolaris/Curvularia

1 Aspergillus/Acremonium


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