Pathergy

Pathergy is a skin condition in which a minor trauma such as a bump or bruise leads to the development of skin lesions or ulcers that may be resistant to healing. Pathergy can also lead to ulcerations at the site of surgical incisions.

Pathergy seen with both Behçet's disease and pyoderma gangrenosum. A highly similar phenomenon known as Koebner occurs in autoimmune diseases such as psoriasis and systemic lupus erythematosus, among others.