Allergic fungal sinusitis (AFS) is recognized by most rhinologists as an allergic reaction to fungi. This condition leads to the formation of fungal debris, allergic mucin, and nasal polyps within the nasal cavity and paranasal sinuses. The fungi responsible for AFS are typically dematiaceous fungi. Common genera include Bipolaris, Curvularia, Exserohilum, Alternaria, Drechslera, Helminthosporium, and Fusarium. Aspergillus is also implicated, but less frequently compared to dematiaceous fungi in Afs Diagnosis.
Manning’s 1996 literature review identified 263 AFS cases. Among the 168 cases with positive fungal cultures, dematiaceous genera accounted for 87%, while Aspergillus was found in only 13%. This highlights the predominant role of dematiaceous fungi in AFS diagnosis.
The University of Texas Southwestern Medical Center, as the largest single institution reporting on AFS, has provided valuable insights into AFS diagnosis. Their evaluations indicate Bipolaris and Curvularia as the most prevalent pathogens, with similar occurrence rates in both adult and pediatric AFS diagnosis. These findings are consistent with broader reviews, reinforcing Bipolaris and Curvularia species as the most commonly identified fungi in AFS.
Geographical location influences the type of fungi involved in AFS diagnosis. Studies show a higher prevalence of Bipolaris species in western and inland regions. Conversely, Curvularia species are more frequently recovered in the Southeast. Interestingly, Aspergillus was found in 13% of adult AFS cases at UT Southwestern but was absent in children. However, a study from India reported only Aspergillus species in all 11 AFS patients where fungus was identified, suggesting regional variations in fungal etiology for AFS diagnosis.
The nature of AFS, whether infectious or allergic, has been a point of debate. Manning and Holman addressed this controversy in two distinct studies, providing clarity for AFS diagnosis. In the first study, they compared 8 patients with culture-positive Bipolaris AFS to 10 controls without AFS. Both groups underwent radioallergosorbent test (RAST) and enzyme-linked immunosorbent assay (ELISA) inhibition for Bipolaris-specific IgE and IgG antibodies, as well as skin testing with Bipolaris antigen. All AFS patients showed positive skin test reactions and positive RAST and ELISA inhibition for Bipolaris-specific IgE and IgG. In contrast, 8 out of 10 control subjects had negative results in both skin and serologic testing. This strongly suggests the crucial role of allergy to fungal antigens in the pathophysiology of AFS diagnosis, confirmed through both in vivo and in vitro tests.
In a related study, sinus mucosal specimens from 14 AFS patients and 10 controls were analyzed. Immunohistochemical analysis focused on eosinophilic mediators (major basic protein and eosinophilic-derived neurotoxin) and a neutrophil-derived mediator (neutrophil elastase) to understand the inflammatory basis of AFS diagnosis. Eosinophil-derived mediators were significantly more prevalent in AFS patients (P<0.001), while neutrophil-derived mediators showed no significant difference between the groups. This further emphasizes the eosinophilic nature of inflammation in AFS diagnosis, pointing towards an allergic rather than infectious process.
Feger et al. further supported the concept of eosinophilic activation in AFS diagnosis by measuring eosinophilic cationic protein levels in serum and mucin of AFS patients. While serum levels were similar between AFS patients and controls, mucin eosinophilic cationic protein levels were significantly elevated in AFS patients (P<0.05). This localized eosinophilic activity in mucin reinforces the allergic inflammatory mechanism central to AFS diagnosis.
These immunological and histological studies, notably by Manning et al. and Feger et al., provide substantial evidence that AFS is an immunologically mediated disorder, not an infectious fungal disease. This understanding is critical for accurate AFS diagnosis and management.
Lu-Myers et al. explored socioeconomic factors in patients with allergic fungal rhinosinusitis versus chronic rhinosinusitis. Their study of 186 patients (93 in each group) revealed that chronic rhinosinusitis patients were more likely to be white, older, with higher income, and better access to primary care. Patients with allergic fungal rhinosinusitis, relevant to AFS diagnosis, tended to have higher quantitative serum IgE levels and increased Lund-Mackay scale scores compared to chronic rhinosinusitis patients.
Mostafa et al. investigated vitamin D3 serum levels in AFS rhinosinusitis patients and controls. Their study of 25 AFS patients and 19 controls found significantly lower vitamin D3 levels in AFS patients. This suggests vitamin D3 may have a protective role against the disease, offering a potential avenue for preventative strategies related to AFS diagnosis.
In conclusion, AFS diagnosis relies on understanding its underlying allergic nature and the characteristic fungal and inflammatory profiles. Research consistently points towards an immunologically driven disease, primarily mediated by eosinophilic inflammation triggered by fungal allergens. Accurate AFS diagnosis is crucial for effective management and differentiating it from other forms of rhinosinusitis.
