Pyoderma gangrenosum is a rare skin reaction to a disease or illness, which results in painful skin ulcers. Namely, it is a condition that causes tissue to become necrotic, causing deep ulcers that usually occur on the legs. Despite the similar-sounding name, Pyoderma gangrenosum is not related to gangrene.



Pyoderma gangrenosum usually starts with a small, red bump on the skin, which may resemble a spider bite, a small pimple, red bump or blood blister. Within days, this bump can develop into a large, painful open sore. In other words, the skin then breaks down to a painful ulcer, which may ooze fluid. When the ulcers occur, they can rapidly get bigger and deeper and can lead to chronic wounds. If the patient has several ulcers, they may grow and merge into one larger ulcer.

Pyoderma gangrenosum usually affects the legs, although it can affect any area of skin, including around the head and neck, upper limbs and genitals. Occasionally, it develops around the site of an injury or surgical wound, such as a stoma. Though the wounds rarely lead to death, they can cause fever, severe pain and scarring.



Ii is not certain what causes Pyoderma gangrenosum, but it appears to be a disorder of the immune system. Also, it is often associated with inflammatory conditions, such as ulcerative colitis and Crohn's disease. If a person has Pyoderma gangrenosum, new skin trauma, such as a cut or puncture wound, may result in the formation of new ulcers. This tendency of new ulcers to form from trauma, including surgery, is known as pathergy.


Risk Factors

Pyoderma gangrenosum is most common in people in their 40s and 50s, but can occur at any age. People who have certain underlying conditions, such as inflammatory bowel disease or rheumatoid arthritis, are also at higher risk of Pyoderma gangrenosum. It is also associated with inflammatory conditions, including:

  • Ulcerative colitis
  • Crohn's disease
  • Rheumatoid arthritis



The ulcers associated with Pyoderma gangrenosum often leave scars.



No one can totally prevent Pyoderma gangrenosum. If one has the condition, he or she should try to avoid injuring the skin. Injury or trauma to the skin can provoke new ulcers to form. Although not entirely effective, a control of any underlying condition that may be causing the ulcers may also be of help.