Fungal Sinusitis: Current Trends in Diagnosis and Treatment

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Allergic Fungal Sinusitis

Allergic fungal sinusitis (AFS) colonizes the sinuses of an atopic immunocompetent patient and acts as an allergen, eliciting an immune response. Millar and colleagues[21] describe the similarities between the histologic material obtained from the maxillary sinuses of 5 patients and pathologically diagnosed specimens of allergic bronchopulmonary asperillosis (ABPA). Seven sinus specimens in a series of 119 reviewed by Katzenstein and colleagues[22] contained eosinophils, Charcot-Leyden crystals, and fungal hyphae, histologically resembling ABPA. Allergic Aspergillus sinusitis was the name used to describe this entity. Numerous reports since that time have documented multiple fungi as causative, prompting the name change to allergic fungal sinusitis (AFS). [23,24,25,26,27,28,29]

Patients commonly present with a history of nasal obstruction, polyposis, or a history of multiple sinus procedures. Nasal endoscopy reveals polyposis, allergic mucin, and thick, tenacious debris. A review by Bent and Kuhn[30] defined the criteria for AFS diagnosis. These include:

 

  1. type 1 hypersensitivity confirmed by history, skin testing, or serology;

  2. nasal polyposis; characteristic CT scan;

  3. histologic evidence of eosinophilic mucus without evidence of fungal invasion into sinus tissue; and

  4. positive fungal stain or culture of the sinus contents removed intraoperatively or during office endoscopy.

 

The pathophysiology of AFS remains unclear. Most authorities postulate that a ubiquitous fungus comes in contact with the sinus mucosa and proliferates. In certain predisposed immunocompetent, atopic individuals, this causes an immune reaction producing mucosal thickening and the formation of allergic mucin, fungal concretions, and polyps. The same scenario in a nonatopic host may result in a fungus ball or no sinus disease.

CT reveals:

 

  1. complete unilateral or bilateral opacification of multiple paranasal sinuses;

  2. sinus expansion and erosion of a wall of the involved sinus; and

  3. scattered areas of intrasinus high attenuation amid mucosal thickening on noncontrasted CT. The degree of bone erosion and extension beyond a sinus may mimic aggressive sinonasal neoplasms.[31] MRI demonstrates isointense or slightly hypodense regions on T1-weighted images and marked hypodensity on T2-weighted images, which correlate to fungus, surrounded by mucosal inflammation with increased density.[32]

 

Histologic examination demonstrates allergic mucin containing sheets of eosinophils, necrotic eosinophils, and cellular debris within an amorphous stroma. Charcot-Leyden crystals with hexagonal cross-section and bipyramidal longitudinal section are visualized on high-power examination. Fungal stains highlight the fungal hyphae. The pathologist must closely examine the specimen to rule out mucosal or bony invasion. Fifty-five patients have been treated at our institution with AFS. Cultures positively identified fungal organisms in 49 patients, with 16 containing multiple organisms (Table 1).

Functional endoscopic sinus surgery (FESS) reveals thick, tenacious mucus ranging in color from yellow to green to brown. Curettage, irrigation, and utilization of the microdebrider facilitate removal. The fungal concretions, mycoliths, are sent to pathology for fungal stain and to microbiology for fungal, aerobic, and anaerobic cultures.[33]

Even with the best surgical treatment, it is unlikely that all fungal hyphae and spores can be removed. Therefore, adjunctive medical therapy should be used. Nasal endoscopy is used to establish staging (Table 2), which is the most efficacious modality to follow the response to medical therapy. Critical nasal endoscopy allows for objective staging of the disease. It is also important in the postoperative period; it standardizes disease recurrence definitions and determines the need for further medical or surgical intervention.[33]

Patients who received postoperative steroids were more often maintained in the lower stages (0 and 1). Those who did not receive additional therapy had a higher rate of recurrence necessitating additional surgical intervention.[33] There are no definitive steroid doses, but we recommend oral prednisone, topical nasal steroids, and nasal irrigations. For the average 70-kg male, prednisone is given at the following doses: 60 mg once a day for 3 days, then decreasing the dose by 10 mg every 3 days 20 mg per day is reached. The patient is maintained at this dosage until the 1-month visit. The dosage may be adjusted accordingly at that time.

Fungal directed immunotherapy has been shown to decrease postoperative nasal crusting, re-accumulation of debris, and allergic mucin within the sinus cavities. Maybry and colleagues[34] found that there were no exacerbations of the symptoms generally associated with AFS using this technique. This consisted of patients undergoing dilutional intradermal testing for a panel of fungal agents. Agents for which positive responses were obtained were incorporated into a treatment mixture in the concentration for each antigen that initiated positive whealing.

Children who present with AFS should be given special consideration. The distortion of the normal sinus anatomy requires that the physician have a comprehensive understanding of the growth patterns of children's sinuses because if surgery is performed, there is a greater risk of penetration into the orbit or anterior cranial fossa.[35,36] Medical therapy is similar to that of adults. They should receive initial prednisone doses between 0.5 mg/kg and 1.0 mg/kg followed by a slow taper. However, children who have not achieved their maximum growth potential need to be weaned off the systemic steroid by 6 months regardless of their disease status. The surgeon's threshold for revision FESS should be lowered because continuing steroids carries the risk of long-term complications.[37] Certain measures should be undertaken in children to minimize the adverse effects of steroids. Supplemental calcium in dosages between 1200 mg to 1500 mg and vitamin D (400 IU) are given if a dietary deficiency is suspected (ie due to poor dairy product intake). Both adults and children should receive H2 blockers or proton pump inhibitors to decrease the incidence of peptic ulcers.

A 25-year-old black male presented with unilateral nasal obstruction, postnasal drainage, anosmia, and facial pressure. He had no other medical problems. Physical examination revealed nasal polyposis completely blocking off the right nasal cavity. The CT scan is illustrated in Figures 6 and 7. The patient underwent FESS and debridement of all affected sinus cavities. Figure 8 depicts the fungal debris. Histologic examination revealed allergic mucin and Charcot-Leyden crystals. Fungal cultures contained Curvularia.

Figure 6.

Axial CT scan through the ethmoid sinuses revealing complete opacification of the right anterior and posterior ethmoids as well as the right sphenoid sinus. The hyperdensities are evident within the anterior and posterior ethmoids.

Figure 7.

Coronal CT scan through the osteomeatal complex region. The hyperdensities are evident in the ethmoid and maxillary sinuses. Evidence of previous uncinate resection is evident on the opposite side.

Figure 8.

Gross appearance of the fungal debris on removal from the sinuses.

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