A positive fungal culture does not confirm the diagnosis of allergic fungal sinusitis (AFS), nor does a negative culture exclude it. For example, fungi may proliferate as saprophytic growth in diseased sinuses. Furthermore, mycology laboratories vary in capability, and specimen handling significantly influences the rate of positive fungal cultures in a clinical setting. Allergic mucin remains the most reliable indicator of allergic fungal sinusitis (AFS). Because nasal polyposis and fungal disease in the sinuses are not unique to allergic fungal sinusitis (AFS), other mycotic diseases in the differential diagnosis must be defined and include the following:
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Invasive fungal sinusitis: This condition typically is encountered in patients who are immunocompromised or have diabetes mellitus and is characterized by angioinvasive fungal penetration of tissue. Hypesthesia, local pain, and intranasal necrosis (in an immunocompromised person) strongly suggest invasive fungal sinusitis and help to differentiate this disease from allergic fungal sinusitis (AFS).
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Saprophytic fungal growth: This growth may be found in one or more paranasal sinus cavities of patients who have chronic suppurative rhinosinusitis. Similar growth may occur within nasal debris of patients who have undergone aggressive sinonasal surgery or those who have rhinitis sicca. Although fungal cultures may be positive, the absence of gross and histiologic findings of allergic mucin and the lack of clinical manifestations of invasive fungal sinusitis suggest saprophytic fungal growth.
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Mycetoma, aspergilloma, or fungus ball of the sinuses: This clinical entity differs from allergic fungal sinusitis (AFS) in presentation. Rather than involving multiple sinuses, a fungus ball typically involves a single sinus, most often the maxillary antrum or sphenoid. Patients affected by this condition are not necessarily allergic and generally do not exhibit nasal polyps. On histologic examination, the material removed from the sinuses demonstrates only fungal hyphae without eosinophils. Surgery in such patients generally is curative.
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Eosinophilic mucin sinusitis: Pansinusitis, polyposis, and mucin that is clinically indistinguishable from that of allergic fungal sinusitis (AFS) are characteristic. However, examination of mucin reveals no fungal hyphae. Allergy is not as constant a feature in this condition as it is in allergic fungal sinusitis (AFS), but asthma is observed more frequently. Ferguson has suggested that this condition may represent a variant of the Samter triad.
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Left middle meatus with suctioning of thick allergic mucin from the ethmoid bulla in the center of the picture; the end of the suction is in the inferior portion of the picture.
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The viscosity of a thick allergic mucin being suctioned from the nasal cavity and vestibule in a patient with allergic fungal sinusitis.
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View just inside the nasal vestibule showing diffused polyposis extending into the anterior nasal cavity and vestibule; the septum is on the right, and the right lateral vestibular wall (nasal ala) is on the left. The polyps all are in the center. The polyps almost hang out of the nasal vestibule.
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A 15-year-old boy with allergic fungal sinusitis causing right proptosis, telecanthus, and malar flattening; the position of his eyes is asymmetrical, and his nasal ala on the right is pushed inferiorly compared to the left.
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A 9-year-old girl with allergic fungal sinusitis displaying telecanthus and asymmetrical positioning of her eyes and globes.
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Coronal CT scan showing extensive allergic fungal sinusitis involving the right side with mucocele above the right orbit and expansion of the sinuses on the right.
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Typical view of a middle meatus in a patient with allergic fungal sinusitis with expansion of the ethmoid complex and extension of the middle turbinate more inferiorly. This is a postoperative view.
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Coronal CT scan showing typical unilateral appearance of allergic fungal sinusitis with hyperintense areas and inhomogeneity of the sinus opacification; the hyperintense areas appear whitish in the center of the allergic mucin.
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Coronal MRI showing expansion of the sinuses with allergic mucin and polypoid disease; the hypointense black areas in the nasal cavities are the actual fungal elements and debris. The density above the right eye is the mucocele. The fungal elements and allergic mucin in allergic fungal sinusitis always look hypointense on MRI scanning and can be mistaken for absence of disease.
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Immediate postoperative 30° angled view showing the complete removal of polyps with a widened frontal sinus recess superiorly and widened ethmoid cavity in the mid portion. The middle turbinate is on the right, pushed against the septum. The lateral nasal wall is on the left.
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Fungal ball in the right maxillary sinus.
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Fungal debris being removed from the ethmoid complex. A suction device is seen in the right lower corner of the picture.
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Allergic mucin, fungal debris, and polyps are shown after removal from the patient. The scale is in inches.
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Coronal CT scan showing the postoperative view following removal of disease after significant disease recurred on both the right and left sides of the nasal cavity and sinuses; mild mucosal thickening of all involved sinuses is present, with some moderate thickening of the left maxillary sinus. All disease, even the lateral mucocele, was removed or drained endoscopically.
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Two-week postoperative endoscopic picture showing polypoid thickening already in the ethmoid cavities while the patient was still on tapering steroids; on the left is the lateral nasal wall. The right shows the middle turbinate next to the septum.
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A polypoid recurrence in the center of the ethmoid cavity. The septum is on the left.
