Pyoderma gangrenosum is a disorder that can be idiopathic or associated with several systemic conditions, the most frequent being inflammatory bowel disease (in particular ulcerative colitis), rheumatoid arthritis, paraproteinemia (mainly IgA), and hematologic neoplasias.1- 3 Pathergy is also commonly seen in patients with PG and usually presents because of a previous mild lesion, such as a needle puncture.2 Pathergic reaction, which was observed as a skin lesion (pustule or papule) by Blobner4 in 1937, appears some hours after a puncture on the skin and is nonspecific. It has also been described in other conditions such as Behçet disease, rheumatoid arthritis, sarcoidosis, idiopathic erythema nodosum, and genital herpes.
Castro-Durán J, Martín-Armada M, Jiménez-Alonso J. Pyoderma Gangrenosum Induced by Acupuncture in a Patient With Ulcerative Colitis. Arch Intern Med. 2000;160(15):2393. doi: