Allergic Fungal Sinusitus

Allergic Fungal Sinusitis

Senior Surgery

January 16, 2005

Fungal sinusitis currently encompasses four different histologic categories with allergic fungal sinusitis (AFS) being the most common. The other three, in order of decreasing frequency, include mycetoma (also known as a "fungus ball"), chronic invasive fungal sinusitis, and acute fulminant fungal sinusitis (Granville). AFS and mycetoma are seen in immunocompetent patients while the chronic invasive and acute fulminant forms are seen in immunocompromised patients. This group of diagnoses range from merely irritating AFS to rapidly fatal acute sinusitis. Invasive disease rarely occurs in AFS (Cox and Perfect).

In recent years, there has been an increase in the number of reported AFS cases (Tichenor), and Cox and Perfect suggest that this is due to lack of awareness on the physician's part, a view that will likely change with the recent attention given to allergic fungal sinusitis. In a retrospective study by Granville, AFS was initially misdiagnosed in 47 percent of cases that had the typical features of AFS. AFS is benign and noninvasive and is attributed to an IgE-mediated hypersensitivity response to fungi in the paranasal sinuses, most frequently the frontal and ethmoidal sinuses. The process begins with an obstruction of the nasal passageway from polyps, inflamed mucosa from chronic sinusitis, a deviated septum, or any (WOULD TAKE OUT ANY) other obstructive process. Fungi then become entrapped in the normal mucous and stimulate the hypersensitive reaction (Cox and Perfect). This theory is not without argument. In fact, in September of 1999, Ponikau et. al. from the Mayo Clinic in Rochester proposed that AFS be renamed eosinophilic fungal rhinosinusitis (EFRS) as they believe that the underlying physiology is the presence of eosinophils in the allergic mucin, not a type I hypersensitivity reaction. This is because almost as much fungi were found in normal controls, (but the difference was that) (CHANGE TO: the difference being) there were no eosinophils in the mucin of the normal controls, only in those with AFS. As late as 1994, however, another group from the Mayo Clinic felt (THEORIZED, instead of felt) the disease was IgE-mediated (Cody). Today, the two terms are sometimes used interchangeably, though McClay and Marple make a subtle distinction in that fungi are not identified in the allergic mucin in EFRS. For a diagnosis of AFS, on the other hand, (delete prepositional phrase (on the other hand) the presence of fungi must be proven, either by hematoxylin & eosin (H & E) or Gomori methenamine silver (GMS) stains or culture. Tichenor states that while the Mayo Clinic's theory did not gain much support initially in 1999, new research will prove them correct.

It was originally thought that Aspirgillus was the main culprit of AFS. (INSTEAD: Aspirgilus was originally discussed as the main etiologic organism.) However, DeShazo has published several studies concluding that 75 percent of AFS cases are caused by dematiaceous molds and only 10 to 20 percent are attributable to Aspirgillus. The most common mold indicated is Bipolaris (80 percent of cases according to Granville) followed by Curvularia. As noted earlier, AFS occurs in immunocompetent hosts. The typical patient is young and has a history chronic sinusitis not responsive to antibacterial agents (Cox and Perfect). Generally these patients have had symptoms of sinusitis for months and have a history of other allergic processes such as atopy or asthma. Most have nasal polyps (Cox and Perfect). Radiographs will show opaque sinuses and thickened mucosal surfaces.

There are two requirements for diagnosis. The first is the presence of "allergic mucin" which is mucus containing necrotic debris and eosinophils with Charcot-Leyden crystals. This mucin has the color and consistency of peanut butter (Granville). The second requirement is the presence of fungi by either stain or culture. H & E stain will show allergic mucin with necrotic debris and eisonophils with Charcot-Leyden crystals while a GMS stain will reveal hyphae in the