Pyoderma gangrenosum (PG), which can be associated with rheumatoid arthritis and inflammatory bowel disease, is a difficult disease to diagnose and treat. Traditionally PG has been considered a "diagnosis of exclusion" but the disease has several characteristic features. These include pathergy-> PG ulcers often appear at a sites of minor trauma. Another characteristic of the disease is the rapid evolution of the lesions-> they first appear as papules or pustules and then they rapidly ulcerate. On clinical exam cribriform or "wrinkled paper" scars at sites of healed ulcers can also aid in the diagnosis of PG. The ulcers themselves have a zone of peripheral erythema, undermined borders and are very tender. Unfortunately PG is often misdiagnoses or over diagnosed leading to mismanagement of one of the most devastating dermatologic diseases. A group of international experts recently came together to develop diagnostic criteria for this disease. It is the hope that these criteria will help aid physicians in diagnosing PG and clinical researchers conduct well-designed clinical trials. This research was recently published in JAMA Dermatology. Please see the following link.