Allergic fungal sinusitis: Detection of Universal Fungal, Aspergillus and Bipolaris DNA in sinus aspirate using polymerase chain reaction and evaluation of Aspergillus specific IgE

Allergic fungal sinusitis (AFS) is believed to represent a hypersensitivity reaction to fungal antigens. The pathophysiology of AFS is still not clearly understood. It is believed that it is not a true fungal infection, but an allergic response to fungal organisms that have colonized the sinus mucosa and secondarily cause a hypersensitivity reaction in the host. However, some patients with AFS do not have allergy to the fungi identified in their eosinophilic mucous but may have elevated IgE levels to other fungi. The patients are usually atopic to multiple aeroallergens. Early reports noted primarily Aspergillus species in allergic mucin, but more recently, the dematiaceous fungi, which include Bipolaris, Curvularia, Alternaria and Helmenthosporium species have been identified in most AFS cases. PCR is significantly more sensitive than nasal swabs cultures in detecting the presence of fungi in nasal mucosa. In our study, 68 cases were selected and sinus aspirates were withdrawn whereas a part of the mucous was used for fungal culture and the other part was used for PCR assay for universal fungal , Aspergillus and Bipolaris DNA. Measurement of Aspergillus specific IgE in sinus aspirate and serum total IgE were done. A control group (10 cases) was included. Among the total number of AFS (68), only 42 cases gives positive fungal growth with a percentage of 61.7 % while among 10 control cases, only 3 cases gives positive growth with a percentage of 30%. Regarding AFS (42 cases), Dematiaceous family was the most common as it was isolated from 30 cases (71.4%). Bipolaris was the most common isolated species (18 cases) followed by Curvularia (11 cases) and Alternaria (1 case). Aspergillus family was isolated from 11 cases (26.1 %). Aspergillus fumigatus was more common as it was isolated from 8 cases followed by Aspergillus niger (3 cases). The results of PCR assay assured the detection of fungal DNA in all cases of AFS group (68 cases) and in 4 cases of control group (40%). Aspergillus DNA was detected in 15 cases (22.05%) while Bipolaris DNA was detected in 27 cases (39.70%). Ten patients were positive for Aspergillus fumigatus specific IgE (14.7 %) out of 68 patients and the mean value was 11.32 ±4.12 IU/ml which was significantly higher than the mean value of this specific IgE in our control group which was 0 IU/ml. Also, only 7 patients from the above 10 patients were positive to Aspergillus fumigatus by PCR (5 only gives positive culture) and this indicates that 3 patients were negative to Aspergillus fumigatus either by culture or PCR but they showed Aspergillus fumigatus allergen specific IgE, on the other hand, 8 cases were positive to Aspergillus fumigatus by PCR and 3 cases were positive by culture failed to show any Aspergillus fumigatus specific IgE indicating that the presence of fungus is not essentially accompanied with allergic process.