Allergic fungal rhinosinusitis (AFRS) has been defined by the following characteristics: presence of nasal discharge, nasal obstruction, decreased sense of smell or facial pressure for 12 weeks, mucin within the sinus cavity containing fungal hyphae and degranulating eosinophils, endoscopic evidence of nasal polyps within the sinus cavity, computed tomography (CT) or MRI findings consistent with chronic impaction of eosinophilic mucin within diseased sinuses, evidence of fungal-specific IgE by skin prick or serum IgE testing, and no evidence of invasive fungal disease. Fungal culture is variably sensitive, therefore the histologic appearance of fungal elements within eosinophilic mucin remains the more reliable indicator of AFRS. This is a well written review of the pathophysiology of allergic fungal rhinosinusitis (AFRS), which is not fully understood and is in constant evolution. Although initial theories favoured an immunoglobulin E-mediated immune response to fungal antigens as having a primary role in the immunopathologic process of AFRS, the purpose of this review was to highlight recent studies that suggest a more complex, epithelial cell-driven immune response being central to the pathophysiology. Recent studies demonstrate a central role of cytokines derived from respiratory epithelial cells, including interleukin (IL)-25, IL-33, and thymic stromal lymphopoietin, in the orchestration of both innate and adaptive T helper 2 (Th2) immune responses that are important components of the immunopathology of chronic rhinosinusitis with nasal polyposis and AFRS. In addition, the robust Th2 adaptive response may be mediated by both fungal antigens and Staphylococcus aureus superantigens. Given the evolving understanding of AFRS pathophysiology, management continues to focus on minimising the burden of the inflammatory trigger(s) and suppressing the inflammatory cascade. This is primarily accomplished through surgery and corticosteroid therapy. Immunotherapy, antimicrobial therapy and other immunomodulatory medications may help mediate the disease process as well.

Current understanding of allergic fungal rhinosinusitis and treatment implications.
Plonk DP, Luong A.
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Susan A Douglas

Sheffield, UK.

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