The fungal conundrum

Allergic Aspergillus Rhinosinusitis

Allergic fungal rhinosinusitis (AFRS) is a unique variety of chronic polypoid rhinosinusitis usually in atopic individuals, characterized by presence of eosinophilic mucin and fungal hyphae in paranasal sinuses without invasion into surrounding mucosa. It has emerged as an important disease involving a large population across the world with geographic variation in incidence and epidemiology. The disease is surrounded by controversies regarding its definition and etiopathogenesis. A working group on "Fungal Sinusitis" under the International Society for Human and Animal Mycology (ISHAM) addressed some of those issues, but many questions remain unanswered. The descriptions of "eosinophilic fungal rhinosinusitis" (EFRS), "eosinophilic mucin rhinosinusitis" (EMRS) and mucosal invasion by hyphae in few patients have increased the problem to delineate the disease. Various hypotheses exist for etiopathogenesis of AFRS with considerable overlap, though recent extensive studies have made certain in depth understanding. The diagnosis of AFRS is a multi-disciplinary approach including the imaging, histopathology, mycology and immunological investigations. Though there is no uniform management protocol for AFRS, surgical clearing of the sinuses with steroid therapy are commonly practiced. The role of antifungal agents, leukotriene antagonists and immunomodulators is still questionable. The present review covers the controversies, recent advances in pathogenesis, diagnosis, and management of AFRS.

Distinctions between Allergic Fungal Rhinosinusitis and Chronic Rhinosinusitis

Background

Recent reports have attempted to redefine the accepted diagnostic criteria for allergic fungal rhinosinusitis (AFRS), a form of chronic rhinosinusitis (CRS) with nasal polyps. As a result, the existence of AFRS as a distinct entity has been questioned, suggesting that allergy has no role in CRS with sinonasal eosinophilia, and the condition should be referred to as eosinophilic fungal rhinosinusitis. The purpose of the study was to differentiate between AFRS and CRS by studying antibody responses in these two clearly defined patient groups.

Methods

Ninety-nine patients were enrolled and classified as AFRS or CRS (without AFRS). Serum total IgE, IgG anti–Alternaria-specific antibodies (UniCAP 100), and IgE antifungal antibodies (immunoblotting) were compared between the groups.

Results

Sixty-four patients fit the traditional criteria for AFRS, with 35 as CRS. Mean serum total IgE and mean IgG anti–Alternaria-specific antibodies were statistically significantly increased in AFRS over CRS patients. There was also a statistically significant increase in the mean number of IgE antifungal bands from AFRS compared with CRS patients.

Conclusion

We have shown a clear immunologic difference between AFRS and CRS patients. The overwhelming evidence of increased total IgE and fungal-specific IgE in AFRS supports an allergic component in AFRS. IgG anti–Alternaria-specific antibodies also point to an exaggerated fungal immune response in these patients. These results support the existence of AFRS as a separate, distinct entity of CRS. It is important to recognize AFRS to ensure proper treatment in these patients.

Allergic fungal sinusitis: pathophysiology, diagnosis and management

Allergic fungal sinusitis (AFS) is a noninvasive form of fungal rhinosinusitis with an incidence of between 6 and 9% of all rhinosinusitis requiring surgery. Regional variation in incidence has been reported, with the southern and southwestern US particularly endemic. Patients with AFS commonly present with chronic rhinosinusitis with nasal polyps, inhalant atopy, elevated total serum immunoglobulin E (IgE), and sinus-obstructing inspissates of a characteristic extramucosal 'peanut buttery' visco-elastic eosinophil-rich material called 'allergic mucin' that contains sparse numbers of fungal hyphae. Sinus CT is always abnormal, showing findings of chronic rhinosinusitis that often include central areas of increased contrast ('hyperattenuation') within abnormal paranasal sinuses that represent the presence of fungal-containing allergic mucin. AFS has been found to be analogous in several ways to allergic bronchopulmonary aspergillosis (ABPA). Both are chronic inflammatory respiratory tract disorders that are driven by hypersensitivity responses to the presence of small numbers of extramucosal fungi found growing within airway-impacting allergic mucin. AFS allergic mucin typically cultures positive for either dematiaceous fungi such as Bipolaris spicifera or Curvularia lunata, or Aspergillus species such as A. fumigatus, A. flavus or A. niger. As with ABPA, patients have type I immediate hypersensitivity to the etiologic mold in AFS. Further, both AFS and ABPA have been found to have association with specific class II major histocompatibility alleles. Proper diagnosis of AFS and differentiation from the other forms of both noninvasive and invasive fungal rhinosinusitis requires strict adherence to published diagnostic criteria. Medical treatment of AFS has been modeled to an extent after treatment approaches for ABPA that includes the use of postoperative oral corticosteroids and aggressive antiallergic inflammation therapy. The use of follow-up measurements of total serum IgE during treatment of both AFS and ABPA patients can help to monitor disease activity. Future AFS research will lead to further insights into pathogenesis, improved treatments, and ultimately decreases in surgical recurrence rates for this highly recurrent hypertrophic rhinosinusitis disorder.

Chronic rhinosinusitis in adults

There is no consensus on diagnostic criteria for chronic rhinosinusitis. By convention, the symptoms of chronic rhinosinusitis are similar to those of acute rhinosinusitis but last more than 8 weeks. Diagnosis is based on history, physical examination, and computed tomography scan of the sinuses or rhinoscopy. Treatment options are numerous and, for the most part, not evidence based. They include antibiotics, nasal or oral corticosteroids, antihistamines, naval lavage, decongestants, immunotherapy, and surgery. Which diagnostic and therapeutic options to exercise when, is the focus of this article.