Nodular granulomatous fungal skin diseases of cats in the United Kingdom: a retrospective review.

IDEXX Laboratories database of cases submitted from the UK between March 2005 and February 2008 (36 months) was investigated for feline nodular granulomatous skin disease associated with fungal infection. Cytological and/or histological slides were reviewed and the diagnosis was based on the microscopic pattern of the inflammatory response and morphology of the causative organism. Aetiological diagnoses were hyalohyphomycosis (64 of 77 cases), phaeohyphomycosis (five of 77 cases) and dermatophytic pseudomycetoma (eight of 77 cases). All cases of hyalohyphomycosis were suspected to be alternariosis based on common features including anatomical distribution of lesions (48 of 64 cases involved the nostril and bridge of nose, face and ears), pattern of histological changes, morphology of the causative organism and results of fungal culture (Alternaria three of 16 and 'saprophyte' nine of 16 cases). Cases of phaeohyphomycosis were demographically and histologically similar to those of alternariosis, except the causative organisms were deeply pigmented brown and had a variety of morphologies that were different from Alternaria. Dermatophytic pseudomycetomas had a characteristic histological pattern including the presence of fungal microcolonies or grains within the tissue. These occurred most often on the trunk (five of eight cases) and four of eight cases were in Persian cats. These findings indicate that alternariosis is by far the most common nodular fungal skin disease of cats in the UK.