Granulomatous dermatitis of the auricolar pinna in a heifer.

This study is aimed to describe the morpho-pathological and etiopathogenic aspects of a unique case of granulomatous dermatitis. A 2 y.o. Italian Friesian heifer showed a papillomatous-like lesion at the edge of the right auricular pinna. The lesion sized 9 cm x 11.5 cm, was exophytic, globular in shape, firm and with the outer surface uneven, depigmented and ulcerated. Cytological examination revealed the presence of an inflammatory population mainly composed by neutrophils and macrophages. On the basis of the cytological observation, the mass was excised and subjected both to histological staining (H&E, PAS, Gram) and molecular biology examination (PCR). The histological examination allowed the diagnosis of a pyogranulomatous inflammation characterized by a epithelioid and giant cells, neutrophilic and macrophagic infiltrate organized around focal areas of eosinophilic homogeneous material consistent with the Splendore-Hoeppli phenomenon. PAS staining highlighted numerous coccoid formations within the piogranulomatous reaction or freely standing in the tissue. Gram stain revealed Gram-positive bacterial colonies confirmed by PCR as Corynebacterium mucifaciens. Granulomatous dermatites are caused by agents against whom the body is sensitized and react through an immunomediated response(1). Sometimes the above reactions are histologically characterized by the Splendor-Hoeppli phenomenon that may represent the deposition of antigen-antibody complexes (immunoglobulins and major basic proteins) and debris from the host inflammatory cells(2). The lesion described in this work seemed worth of description because of the etiologic agent. In fact, Corynebacterium mucifaciens is a newly-described species belonging to the the largest genus in the group of coryneform bacteria(3). Moreover, the seat of development was extremely atypical for the bovine species. Corynebacterium mucifaciens is better differentiated from closely-related species by molecular biology techniques, such as sequencing of the 16S rRNA gene and is isolated from human blood or other normally-sterile body fluids, often considered as part of the normal skin flora or contaminants. To date, literature data report the occurrence of disease due to Corynebacterium mucifaciens only in humans where it has been related to severe infections, lethal bacteremia (4), cavitary pneumonia (5), corneal ulcer (6), otitis and nasal polips (7). To the author’s knowledge, this is the first report of a lesion induced by C. mucifaciens in veterinary medicine.