What is the evidence to support an immunologic theory of the etiology of allergic fungal sinusitis (AFS)?

Updated: Mar 16, 2018
  • Author: John E McClay, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

Controversy has existed over whether the disease is infectious or allergic. Manning and Holman objectively addressed this controversy in 2 separate studies. [10] In the first study, 8 patients with culture-positive Bipolaris allergic fungal sinusitis (AFS) were prospectively compared with 10 control subjects who did not have allergic fungal sinusitis (AFS). Both groups were evaluated with (1) radioallergosorbent test (RAST) and enzyme-linked immunosorbent assay (ELISA) inhibition to Bipolaris -specific IgE and IgG antibodies and (2) skin testing with Bipolaris antigen. All 8 patients had positive skin test reactions to Bipolaris antigen and positive RAST and ELISA inhibition to Bipolaris -specific IgE and IgG. Eight of the 10 control subjects had negative results on both skin and serologic testing, implicating the importance of allergy to fungal antigens (both in vivo and in vitro) in the pathophysiology of allergic fungal sinusitis (AFS).

In a complementary study, sinus mucosal specimens from 14 patients with allergic fungal sinusitis (AFS) were compared with those from 10 control subjects who did not have allergic fungal sinusitis (AFS). Immunohistochemical analysis for eosinophilic mediators (major basic protein and eosinophilic-derived neurotoxin) and a neutrophil-derived mediator (neutrophil elastase) was performed to assess the underlying nature of inflammation. Eosinophilic-derived mediators were much more common (P< 0.00001) than neutrophil-derived mediators in the allergic fungal sinusitis (AFS) group, whereas significant differences were not observed in the control group. The predominance of eosinophilic-derived mediators further supports the association between noninfectious (ie, allergic) inflammation and allergic fungal sinusitis (AFS).

The concept of eosinophilic activation associated with allergic fungal sinusitis (AFS) was further emphasized by Feger et al, who studied eosinophilic cationic protein levels in the serum and mucin of patients with allergic fungal sinusitis (AFS). No differences in serum eosinophilic cationic protein were detected between patients with allergic fungal sinusitis (AFS) and control subjects, but eosinophilic cationic protein levels were significantly higher in the mucin of patients with allergic fungal sinusitis (AFS); P < 0.01).

Studies such as those by Manning et al and Feger et al offer strong immunologic and histologic data to support the argument that allergic fungal sinusitis (AFS) represents an immunologically mediated disorder rather than a point on the spectrum of infectious fungal disease. [11]

A study by Lu-Myers et al found that socioeconomic factors differed between patients with allergic fungal rhinosinusitis and those with chronic rhinosinusitis, with the latter tending to be white and older, with a higher income and greater access to primary care. The study, which involved a total of 186 patients (93 patients in each group), also found that patients with allergic fungal rhinosinusitis tended to have greater quantitative serum IgE levels and higher Lund-Mackay scale scores than did patients with chronic rhinosinusitis. [12]

A study by Mostafa et al found serum levels of vitamin D3 to be significantly lower in patients with allergic fungal rhinosinusitis than in controls. The investigators suggest that the agent may serve as a prophylactic against the disease. The study included 25 patients with allergic fungal rhinosinusitis and 19 controls. [13]


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