FINAL DIAGNOSIS: ALLERGIC FUNGAL SINUSITIS SECONDARY TO BIPOLARIS SPP
Allergic fungal sinusitis (AFS) is a slowly progressive, non-invasive form of paranasal sinus mycosis. The disease is relatively common and usually occurs in immunocompetent individuals, most of whom lack a history of atopy.1 The patient usually complains of nasal congestion, but the disease may progress to present as a mass lesion, as in the case described herein. Untreated, multiple sinuses may be involved, with sinus wall erosion resulting from pressure. When particularly extensive, this may result in anosmia due to involvement of the cribriform plate, visual disturbances due to orbital involvement, and epidural, subdural, or intracranial abscesses following extension through the skull base into the cranial cavity.1 Histologic examination reveals sinonasal polyposis in a background of allergic mucin. Silver stains often reveal fungal hyphae, but unfortunately the specimen is only rarely cultured.2 Originally, Aspergillus species were commonly designated as the etiologic agent. Several clinicopathologic studies have correlated cultures of sinonasal contents with the histologic features of the fungal organisms.2,3,4,5 Surprisingly, the most common etiologic agents for AFS are members of the dematiaceous family (81% of AFS). Bipolaris is the most common genus recovered, followed by Curvularia. Other members of the dematiaceous family that have been reported include Exserohilum and Alternaria. Fortunately, noninvasive AFS usually responds well to surgical debridement and aeration of the sinuses. Systemic and topical corticosteroids may be of use as well. 1,2,6 In this case, the patient responded well to surgical debridement and sinus aeration and was discharged one week following surgery. He is recovering well and is being followed for recurrence.
Phaeohyphomycosis is the term used to describe infections caused by the diverse group of dematiaceous molds. The term phaeohyphomycosis is used for infections caused by rapidly growing molds, including Bipolaris, Alternaria, Curvularia, Exophiala, and Exserohilum species. The slower growing dematiaceous molds are the etiologic agents of chromomycosis and eumycotic mycetoma. 8,9 All of the dematiaceous molds are characterized by dark gray, brown or black colonies in culture. The various genera are best identified by differences in fruiting bodies and conidiation. Bipolaris species are differentiated by the production of germ tubes arising from the end cells of the conidium. The conidium has 3-5 septa. While phaeohyphomycosis is usually a superficial cutaneous infection, rarely more severe forms of infection may occur, including sinusitis, keratitis, panniculitis, and invasive/systemic infections. These infections are most commonly seen in immunocompetent hosts, with immunosuppressed hosts presenting with unusual sites of infection.8,9
Contributed by Christine C. Dorvault, MD, E. Leon Barnes, MD, John Sheaffer, and William Pasculle, ScD