Pyoderma Gangrenosum: Diagnostic Criteria, Subtypes, Systemic Associations, and Workup.

Pyoderma gangrenosum (PG) is an inflammatory neutrophilic dermatosis with variable clinical features. The classic presentation is an ulceration with an erythematous to violaceous undermined border. Extracutaneous manifestations may occur. Associated systemic diseases include inflammatory bowel disease, inflammatory arthritides, and hematologic disorders. The pathophysiologic mechanism of disease is not completely known but likely related to the cumulative impact of inflammation, immune-mediated neutrophilic dysfunction, and genetic predisposition. Incidence is between 3 and 10 people per million but may be greater due to under recognition. In this article, we will discuss the diagnostic criteria, disease subtypes, systemic associations, and workup.