Greasy Pig Disease- Staphylococcus hyicus
Haired skin: The epidermis is hyperplastic and multifocally covered by a thick serocellular crust with large numbers of degenerate neutrophils and small colonies of coccoid bacteria. There are occasional follicles dilated by accumulation of neutrophils which in one case infiltrates the wall of the follicle. There is mild superficial dermal edema with infiltration by low numbers of neutrophils and lymphocyctes.
Haired skin: Proliferative and exudative epidermitis, with ulceration – Exudative epidermitis (greasy pig disease)
The bacteria produces an exotoxin called “exfoliatin” which binds to filaggrin in keratohyalin granules causing focal erosions. Lesions commonly develop around the eyes, ears, snout, chin and abdomen, and often are very “greasy” looking due to the exudation of serum and keratin. Folliculitis is common, and there is minimal dermal inflammation unless ulceration is severe. Diagnosis can be made by gross examination, but histopathology and cultures are definitive.