Symptoms and causes


Pyoderma gangrenosum usually starts with a small, red bump on your skin, which may resemble a spider bite. Within days, this bump can develop into a large, painful open sore.

The ulcer usually appears on your legs, but may develop anywhere on your body. Sometimes it appears around surgical sites. If you have several ulcers, they may grow and merge into one larger ulcer.

When to see a doctor

Talk to your doctor if you develop a painful, rapidly growing skin wound.


Pyoderma gangrenosum isn't infectious or contagious, but no one knows exactly what causes it. It's often associated with autoimmune diseases such as ulcerative colitis, Crohn's disease and rheumatoid arthritis. And some studies indicate that it may have a genetic component.

If you have pyoderma gangrenosum, new skin trauma, such as a cut or puncture wound, may trigger new ulcers.

Risk factors

Certain factors may increase your risk of pyoderma gangrenosum, including:

  • Your age and sex. The condition is slightly more common among women. And it usually occurs between the ages of 40 and 50, though it can appear at any age.
  • Having inflammatory bowel disease. People with a digestive tract disease such as ulcerative colitis or Crohn's disease are at increased risk of pyoderma gangrenosum.
  • Having rheumatoid arthritis. People with rheumatoid arthritis are at increased risk of pyoderma gangrenosum.
  • Having blood cancer. People with blood disorders (hematologic malignancies) are at increased risk of pyoderma gangrenosum.


Possible complications of pyoderma gangrenosum include:

  • Infection
  • Scarring
  • Uncontrolled pain
  • Depression
  • Loss of mobility