Fungal balls of the paranasal sinuses are commonly referred to as mycetomas in the literature (though this is a misnomer as mycetomas technically represent superficial fungal infections on the feet) (Ferguson, 2000c). Fungal balls are noninvasive, non-immunogenic types of fungal sinusitis. Patients are immunocompetent and generally are neither atopic nor do they suffer from other disorders specific to the respiratory tract.
The masses themselves are mycelial mats which can rest in the sinus cavities for months or years without any sort of tissue invasion. They are described as cheeselike, gritty, rubbery, or greasy masses that are easily discernible from the surrounding mucosa. They may be black or brownish in color, and often have a fetid odor associated with them. A small, localized inflammatory response may be seen, but the integrity of the nasal architecture is unchanged (Washburn, 1994). The benign mass is usually limited to the maxillary sinus cavity, with infections occurring infrequently in the sphenoid cavity as well. Symptoms include chronic nasal congestion, pain localized to the maxillary sinus, and a postnasal drip. Often a superimposed acute bacterial infection will occur, though the infection is opportunistic and not directly integrated with the fungal sinusitis.
Several species of fungi have been reported in clinical settings as etiological agents involved with noninvasive fungal sinusitis (Table 1.1). The most predominant organisms seen within this disease state are
Table 1.1. Fungal Etiological Agents Associated with Types of Fungal Sinusitis
Type of fungal sinusitis Fungal etiological agents
Noninvasive fungal masses (fungal balls) A. fumigatus, A. flavus, Alternaria species,
Penicillium (Ferguson, 2000b) Invasive (acute and chronic subtypes) A. fumigatus, A. flavus, Alternaria species,
C. neoformans and C. albicans (Ferguson 2000a, Schell 2000)
Chronic rhinosinusitis A. fumigatus, A. flavus, Alternaria species, C. albicans,
Penicillium, Fusarium (Ponikau Sherris et al., 1999) Allergic fungal rhinosinusitis (AFRS) A. fumigatus, Alternaria, Bipolaris, Curvularia
(Ferguson, 2000a; Houser and Corey, 2000)
Aspergillus fumigatus, A. flavus, and species of Alternaria, with Penicillium being seen in extremely rare cases (Schell, 2000). The prevalence of Aspergillus in noninvasive fungal sinusitis parallels the prevalence of this organism as one of the most common airborne fungal pathogens (Latge, 1999).
The exact pathogenesis of noninvasive fungal masses is currently unknown, though the most likely cause is the persistence of the fungal spores within the nasal cavity (Ferguson, 2000c). Normally factors such as mucociliary beat are responsible for clearing fungal spores from the sinus region; however when an antigen is not removed, for reasons that are unclear, it may undergo germination (Baraniuk, 1994). Once hyphal extension transpires, the organism can become too large to be cleared by normal physiological means and is then able to establish an infection, though a nonimmunomodulatory one (Ferguson, 2000c).
Currently the only treatment available for noninvasive fungal sinusitis is surgery to remove the obstruction (Ferguson, 2000c). Irrigation can be useful in washing out small mycelial masses, but in the case of larger masses endoscopic surgery is preferred in targeting both the maxillary and sphenoid sinuses.
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