Dermal arteritis of the nasal philtrum in a Giant Schnauzer and three Saint Bernard dogs.

Arteritis of the nasal philtrum is described in four dogs. Two of the Saint Bernards were related. The lesions were solitary, well-circumscribed, linear ulcers that were neither pruritic nor painful. The age of the dogs at the time the owners first noticed the lesion ranged from 3 to 6 years. The ulcers had been present for 0.5-5 years before diagnosis was pursued. Three of the dogs experienced repeated, mild episodes of arterial bleeding from the ulcers. Two dogs also experienced a severe episode of bleeding that required surgical intervention. Histopathological findings included a V-shaped ulcer, neutrophilic dermal inflammation subjacent to the ulcer and lymphoplasmacytic dermatitis bordering the ulcer. The most remarkable pathological findings were present in the deep dermal arteries and arterioles subjacent to the ulcer. The changes were characterized by subendothelial spindle cell proliferation with marked extracellular matrix deposition that stained blue with Alcian Blue (mucin) and Masson's trichrome (collagen) and resulted in intimal thickening, and stenosis of dermal arteries and arterioles. Immunohistochemical studies suggested that the proliferating spindle cells were of either myofibroblast or smooth muscle origin (actin and vimentin positive). Anti-inflammatory therapy (glucocorticoids; tetracycline and niacinamide; fish oil) may be beneficial for long-term control of this condition, however, long-term maintenance treatment appears to be necessary.