Phaeohyphomycosis by Phialophora verrucosa: first European case in a cat

PHAEOHYPHOMYCOSES are uncommon opportunistic infections in human beings (Rippon 1988, Kwon-Chung and Bennett 1992) and animals (Foil 1998). They are caused by dematiaceous filamentous fungi, showing a melanin-like pigment in the walls of the hyphae and spores. Usually these fungi are plant pathogens, soil saprophytes or laboratory and environment contaminants. Approximately 15 genera of dematiaceous fungi have been recognised as agents of feline pheohyphomycosis. Phialophora verrucosa has been reported as the agent of feline phaeohyphomycosis in Canada (Dion and others 1982, Pukay and Dion 1984). Recently, P verrucosa has been identified as the agent of canine phaeohyphomycosis in Belgium (Remy and others 2001). This short communication describes, to the authors’ knowledge, the first European case of feline phaeohyphomycosis. An eight-year-old, male shorthair cat with an indoor/ outdoor lifestyle was presented with a black mass on its left pinna. The owner reported that the cat was otherwise healthy and that the mass had been observed for the first time one month previously. A solitary, ulcerated, pigmented tumourlike lesion, approximately 3 cm in diameter, was observed on the distal convex surface of the pinna, behind the cutaneous marginal pouch (Fig 1). The mass was firm and localised in the dermal subcutaneous tissue, and had a smooth surface with a small fistula draining black-brown fluid. A general physical examination proved unremarkable. A complete blood count revealed mild anaemia, and biochemical serum analysis showed increased creatinine and blood urea nitrogen (BUN) (Table 1). Urinalysis showed only a mild proteinuria. The ELISA test for feline leukaemia virus antigen was negative, and the test for antibodies to feline immunodeficiency virus (FIV) was positive. A tissue sample of the mass was fixed in 10 per cent buffered formalin, processed routinely, then stained with haematoxylin and eosin and periodic acid-Shiff. Histopathological examination revealed diffuse granulomatous and pyogranulomatous dermatitis and panniculitis with numerous fungal elements. Brown-pigmented, septate, branched and unbranched hyphae were easily detected in all the sections examined (Fig 2). They were surrounded by packed epithelioid macrophages, neutrophils, plasma cells and lymphocytes. Based on the biopsy results, a mycotic granuloma, caused by a pigmented (dematiaceous) fungus suggestive of phaeohyphomycosis, was diagnosed. Cultures of both the aspirate fluid and the biopsy sample of the mass were performed in Mycobios Selective Agar and Sabouraud’s dextrose agar (Biolife). Some slow-growing, blackish fungal colonies, which were dome-shaped at first and then became flattened, developed within 15 days at 27°C. Microscopic examination of the cultured organism revealed chains of smooth, septate hyphae producing typical phialides with a cup-shaped collarette (flared mouth). The phialides were flask-shaped, 3 to 4 μm wide and 4 to 7 μm long, and occurred laterally or on the tip of the hyphae, and appeared singly or occasionally in clusters with or without stalks. Within their necks, elliptical, thin-walled conidia, 1 to 3 μm wide and 2 to 4 μm long, were present. The conidia appeared organised in a mass to form large balls at the tip of the Veterinary Record (2005) 157, 93-94