Pyoderma gangrenosum versus chronic venous ulceration: Comparison of diagnostic features

Background: Diagnosis of pyoderma gangrenosum can be difficult, leading to overdiagnosis or underdiagnosis. Objective: To identify clinical features helpful in establishing a diagnosis of pyoderma gangrenosum and to compare the characteristics of patients with pyoderma gangrenosum with those of patients with chronic venous ulcers. Method: A retrospective chart review was performed in 28 patients with typical pyoderma gangrenosum and compared with the clinical features in 28 patients with chronic venous ulcers. Results: (1) Even when other body sites are affected, pyoderma gangrenosum usually affects the upper and lower legs and feet or peristomal sites compared with chronic venous ulcers that are limited to the lower legs and feet. (2) Pyoderma gangrenosum can be associated with systemic diseases, especially inflammatory bowel disease. (3) Pustules and purulent discharge are features of pyoderma gangrenosum but not of chronic venous ulcers. (4) Crater-like holes or cribriform scarring is commonly seen in pyoderma gangrenosum but not in chronic venous ulcers. (5) Pathergy is a specific but not sensitive finding of pyoderma gangrenosum. It does not occur in patients with chronic venous ulcers. Conclusions: Diagnosis of pyoderma gangrenosum should be considered in patients with purulent ulcers affecting the legs or peristomal sites. To confirm the diagnosis, specific features should be sought, including pathergy, crater-like holes or cribriform scarring, and association with inflammatory bowel disease. Other causes of ulceration should be excluded.