Allergic Fungal Sinusitis: Diagnosis and Treatment
Diagnosis
Allergic fungal sinusitis is definitively diagnosed by histopathologic identification of extramucosal allergic mucin containing fungal hyphae (without tissue invasion), combined with chronic sinusitis, nasal polyposis, and evidence of fungal-specific IgE hypersensitivity. 1
Clinical Presentation in This Patient Population
Allergic fungal sinusitis occurs exclusively in immunocompetent patients with atopic disease, making this teenage patient with documented atopy, asthma, and allergic rhinitis a classic candidate. 2
The constellation of chronic nasal congestion, facial pressure, recurrent sinus infections, and nasal polyps in an atopic adolescent should immediately raise suspicion for allergic fungal sinusitis. 3, 4
In children and adolescents, unilateral facial deformity or proptosis may be present due to dramatic expansion of intrasinal contents, though true tissue invasion does not occur. 2, 5
Diagnostic Work-Up
CT scanning is the imaging modality of choice, typically showing chronic rhinosinusitis with involvement of multiple sinuses and often characteristic hyperattenuating sinus contents (the "peanut butter-like" allergic mucin). 6, 3, 4
Laboratory evaluation should include total serum IgE (usually markedly elevated) and allergy skin testing to fungal organisms (Aspergillus, Bipolaris, Curvularia, Dreschlera), which will be positive in all cases. 1, 3, 4
Peripheral eosinophilia is commonly present but not required for diagnosis. 3, 5
The definitive diagnosis requires surgical histopathology demonstrating three key features: (1) extramucosal allergic mucin with eosinophils and Charcot-Leyden crystals, (2) fungal hyphae within the mucin (identified by special stains such as Gomori methenamine silver), and (3) eosinophilic-lymphocytic mucosal inflammation without tissue invasion. 1, 6, 4
The most commonly implicated organisms are dematiaceous fungi, particularly Bipolaris spicifera in the southwestern United States, though Aspergillus, Curvularia, and Penicillium species are also frequent. 1, 3, 4
Critical Diagnostic Pitfall
- Do not confuse allergic fungal sinusitis with invasive fungal sinusitis—the presence or absence of fungal hyphae within mucosal tissue (tissue invasion) is the critical histopathologic distinction. 6 Invasive disease occurs in immunocompromised patients and requires urgent surgical debridement plus systemic antifungals, whereas allergic fungal sinusitis occurs in immunocompetent atopic patients and does not require antifungal therapy. 6, 2
First-Line Treatment
Complete surgical removal of all allergic mucin and polyps via endoscopic sinus surgery is mandatory as the initial step, followed immediately by postoperative oral corticosteroids to suppress eosinophilic inflammation and prevent recurrence. 3, 4, 7
Surgical Management
Aggressive endoscopic sinus surgery with complete exenteration of all allergic mucin is required before any medical therapy can be effective. 3, 7
Surgery alone is insufficient—recurrence rates remain high (approximately 55% at one year) without aggressive postoperative medical management. 5, 7
Medical Management Post-Surgery
Immediate Post-Operative Phase
A short course of oral prednisone (typically 25–60 mg daily for 5–20 days, then taper) should be initiated immediately after surgery to reduce eosinophilic inflammation, prevent early recurrence, and forestall the need for repeat surgery. 3, 4, 7
Oral corticosteroids have been shown to reduce disease activity and are a cornerstone of postoperative management in allergic fungal sinusitis. 3, 7
Maintenance Therapy
After the initial oral corticosteroid course, maintenance intranasal corticosteroids (twice-daily dosing) must be continued long-term to control inflammation and reduce polyp recurrence. 1, 3, 7
Twice-daily intranasal corticosteroid dosing is more effective than once-daily for optimal control of nasal polyps. 1
Adjunctive Allergy Management
Aggressive allergy management including allergen immunotherapy to the specific fungal organisms is recommended as part of comprehensive treatment. 3, 4, 7
Antihistamines and antileukotriene agents (montelukast) may provide additional benefit as adjunctive therapy, though evidence is mixed. 7
Nasal saline irrigations should be used routinely to improve mucociliary clearance. 5
Critical Treatment Pitfalls
Systemic antifungal agents are NOT indicated in allergic fungal sinusitis because there is no tissue invasion—this is an immunologically mediated hypersensitivity reaction, not an infection. 6, 8, 3
Do not rely on surgery alone—medical management with oral corticosteroids postoperatively is essential to prevent the high recurrence rates seen with surgery alone. 3, 7
Close follow-up with serial total serum IgE measurements is prognostic—rising IgE levels postoperatively may predict disease recurrence and prompt earlier intervention. 3, 7
Long-Term Management Strategy
Coordinated medical-surgical co-management is crucial because early recognition of recurrence and prompt repeat surgery combined with aggressive medical therapy yields the best outcomes. 3, 4, 7
Regular endoscopic surveillance is necessary given the high recurrence rate, particularly in adolescents with asthma and extensive disease. 5, 7
Patients with asthma and nasal polyps have more difficult-to-control disease, requiring particularly aggressive medical management. 1