Phaeohyphomycosis and onychomycosis due to Chaetomium spp., including the first report of Chaetomium brasiliense infection.

Chaetomium species have been rarely described as aetiological agents of invasive and dermatomycotic infections in humans. The majority of cases have been reported within the last two decades. Treatment failed in most of these cases. In this paper we present two cases in which Chaetomium spp. can be clearly identified as an aetiological agent in pathological conditions. In the first report, we describe a new aetiological agent, Chaetomium brasiliense, which was implicated in a case of otitis externa in a patient with spinocellular carcinoma basis cranii. The patient had been repeatedly treated for relapsing otitis externa and had previously undergone surgery several times for otitis media. The fungal aetiology was confirmed by repeated positive culture and histologic studies. The second case involved onychomycosis with strikingly brown nail discoloration due to Chaetomium globosum in an otherwise healthy patient. The nail lesion was successfully cured by oral terbinafine. The determination of both species was supported by sequencing of rDNA regions. The morphological aspect of Chaetomium spp. identification is also discussed. In vitro antifungal susceptibility tests demonstrated that both isolates were susceptible to terbinafine and azole derivates except fluconazole. Amphotericin B was effective only against the C. brasiliense strain. We review the literature to summarize clinical presentations, histologic findings, and treatment strategies.