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.