Folgoration as an Example of Pathergy in a Patient Affected by Pyoderma Gangrenosum and Takayasu's Arteritis

Pyoderma gangrenosum (PG) is a neutrophilic dermatosis of unknown aetiology. Clinical manifestations of PG are characterized by destructive, necrotizing, and noninfective ulceration of the skin. 20–30% of cases are initiated and aggravated by minor trauma or surgery, a phenomenon named pathergy. PG is related to several autoimmune diseases including ulcerative colitis, Crohn's disease, rheumatoid arthritis, and monoclonal gammopathy. The association with Takayasu's arteritis (TA), a chronic inflammatory and stenotic disease of large and medium-sized arteries, is instead less common. We report a case of PG associated with TA that was induced by an accident with folgoration of the skin; in this case the folgoration can be considered as an exemple of Pathergy, that is, a characteristic feature of PG.