Allergic Fungal Rhinosinusitis: Distinct Clinical Features, Diagnostic Challenges, and Evolving Therapeutic Strategies.

Allergic fungal rhinosinusitis (AFRS) is a distinct, noninvasive endotype of chronic rhinosinusitis with nasal polyps characterized by type 2 inflammation, eosinophilic mucin-containing fungal elements, and dramatic radiographic findings. Despite extensive sinonasal disease with expansile remodeling that may extend into orbital or intracranial spaces, patients often report disproportionately mild symptoms, contributing to delayed diagnosis. This article presents a representative case of unilateral AFRS in a young, immunocompetent patient and uses it as a framework to review current diagnostic criteria, epidemiologic features, radiographic nuances, and common diagnostic pitfalls. We discuss the evolving understanding of AFRS pathophysiology, including emerging immunologic insights that distinguish AFRS from other eosinophilic chronic rhinosinusitis phenotypes. Management remains centered on early, comprehensive endoscopic sinus surgery for removal of eosinophilic mucin, followed by long-term topical anti-inflammatory therapy. Recent observational studies and a randomized controlled trial suggest a role for type 2-targeted biologics as adjunctive therapy in select patients with refractory disease. Recognition of AFRS as a unique clinical entity is essential to ensure appropriate management, avoid unnecessary medical therapy, and prevent disease-related complications.