Pyoderma Gangrenosum By Julia Benedetti, MD, Harvard Medical School Reviewed / Revised Apr 2022 | Modified Sep 2022 View Patient Education Etiology Pathophysiology Symptoms and Signs Diagnosis Treatment Key Points Topic Resources Pyoderma Gangrenosum Ulcerative... Pyoderma Gangrenosum Bullous... Pyoderma Gangrenosum Vegetative... Pyoderma gangrenosum is a chronic, neutrophilic, progressive skin necrosis of unknown etiology often associated with systemic illness and sometimes skin injury.