Allergic Fungal Sinusitis: Controversy and Evolution of Understanding with Therapeutic Implications

Abstract

Fungal rhinosinusitis can be categorized into distinct forms on the basis of histopathology. The invasive manifestations are fulminant or rapidly progressing, chronic or indolent, and granulomatous. The noninvasive manifestations are fungus balls and allergic fungal sinusitis (AFS). A noninvasive and controversial category introduced within the last decade resembles AFS; however, patients are not allergic and are termed nonallergic eosinophilic fungal rhinosinusitis (NA-EFRS). AFS or NA-EFRS is the subject of this chapter and will be contrasted to eosinophilic sinus disease in which fungi are absent.Classically, AFS is defined as the histopathologic presence of eosinophilic mucin containing fungal hyphae retrieved from the nose or paranasal sinuses from patients who demonstrate IgE mediated allergy to the fungus. Patients with AFS often have asthma, peripheral eosinophilia, nasal polyps, and allergic rhinitis. The nose and sinus contents contain green, sticky or tan mucin plugs, which when examined pathologically reveal eosinophilic mucin, Charcot Leyden crystals, degenerating inflammatory cells, and sparse hyphae (Fig. 1 ).The presence of hyphae is considered to be important in making the diagnosis; however, hyphal presence is often sparse and the diagnosis of AFS may be missed due to sampling error [1] . The absence of fungus histopathologically or of allergy has lead to two additional categorizations: (1) Nonfungal eosinophilic mucin rhinosinusitis (NF-EMRS) in which fungi are not seen or cultured and are NOT considered to be of etiologic importance [2] (Fig. 2 ) and (2) Nonallergic eosinophilic fungal rhinosinusitis (NA-EFRS) in which fungi are present and believed to be causal in the pathophysiology through nonallergic mechanisms [3] .

Fungal Rhinosinusitis: A Radiological Review with Intraoperative Correlation

“…Recent research and publications continue to generate more questions than answers regarding this condition [9,10]. Whether fungi drive the inflammatory disease process or are just an associated finding remains a debated topic.…”