The SAM Syndrome
Allergic fungal sinusitis (AFS) is a noninvasive form of fungal sinusitis that is seen in highly atopic individuals with fungal-specific IgE, intractable sinusitis, and nasal polyposis.
Chronic bacterial sinusitis results when large accumulations of eosinophil-rich allergic mucin containing sparse fungal elements cause mucous impaction and obstruction of the osteomeatal complex. Mucous plugs may become an expanding mass that is capable of penetrating the cartilaginous walls of the sinuses laterally into the orbits or superiorly or posteriorly into the cerebrum.
Over 100 case reports of AFS have followed a series of five patients reported in an abstract in 1981 and the first published series of seven patients described by Katzenstein et al in 1983. Subsequently, the diagnostic criteria for AFS were established, and we and others have reported on the clinical features of patients with the condition.
AFS has been suggested to be the upper airway manifestation of a similar process occurring in the lower airways of atopic asthmatic patients, which is now termed allergic bronchopulmonary mycosis (ABPM).
McCarthy and Pepys have reported that 10% of patients with ABPM produce nasal plugs that are similar to the airway casts that are present in the bronchi of patients with ABPM. Safirstein has reported that nasal discharge containing airway casts improved when a patient with ABPM was treated with corticosteroids. The hypothesis that AFS and ABPM share immunopathogenic mechanisms is further supported by the observation that the distinctive, eosinophil-rich, laminated, allergic mucin is the substrate for the mucous plugs that are common to both conditions.
An IgE-driven hypersensitivity response to low-level fungal colonization may be the principal operative mechanism, but abnormalities of local immunity or mucus itself could play a role in predisposing an individual to this process.
In that regard, an association between ABPM and cystic fibrosis (CF) has been reported.
If the mechanisms of AFS and ABPM are similar, it would be likely that individuals with one disease would have the propensity to develop the other and that a number of patients with coexistent disease could be identified. In this study, we provide evidence that this is, in fact, the case.