[Allergic fungal sinusitis: is this rare disease an allergy or infection?].
Allergic Fungal Sinusitis (AFS) is a newly recognized form of benign, non invasive sinusitis the histopathologic features of which are similar to those of allergic bronchopulmonary aspergillosis. AFS is a rare condition. However, because treatment and prognosis vary widely, it is important that this disorder be recognized and differentiated from chronic bacterial sinusitis and other forms of fungal sinusitis. AFS does not discriminate by age although it is primarily found in young adults. AFS patients are usually atopic, often having a history of asthma and nasal polyposis. Many have suffered from the symptoms of chronic sinusitis for years while others have had multiple sinus surgery. Radiographs reveal the involvement of multiple sinuses, often with bone destruction. Laboratory findings support an allergic state with a marked increase in eosinophilia and total IgE. At times RAST testing proves positive for fungi and immediate cutaneous reactivity to fungi is also present. Histologic review of the sinus contents reveals characteristic "allergic mucin", with numerous eosinophiles, Charcot-Leyden crystals and fungal hyphae, without any fungi tissue invasion. A wide variety of fungal agents has been implicated, although the majority belong the Dematiacee family. Those patients with allergic mucin but no documented fungi are indicated as having AFS-like syndrome. The pathogenesis of AFS is uncertain. There is controversy in the literature as to what role hypersensitivity (Gell and Coombs type I and type III responses) in infection play. To date current therapeutic recommendations include complete exenteration of all allergic mucin. Adjunctive, short-term systemic steroids often prove useful and nasal steroid spray should be continued for long term. Systemic antifungal agents are not recommended in AFS. Recurrence is common and thus close clinical, endoscopic and radiographic follow-up is important. The clinicopathologic features of one patient with AFS are reported and etiopathogenetic problems are discussed. The presented case showed a positive culture with negative immunological testing (RAST-positive and immediate cutaneous reactivity to fungal antigen), thus confirming the pathogenetic hypothesis of the saprophytic fungal growth in an atopic patient.