Overview

Pyoderma gangrenosum (pie-o-DUR-muh gang-ruh-NO-sum) is a rare condition that causes large, painful sores (ulcers) to develop on your skin, most often on your legs.

No one knows exactly what causes pyoderma gangrenosum, but it appears to be a disorder of the immune system. People who have certain underlying conditions, such as inflammatory bowel disease or rheumatoid arthritis, are at higher risk of pyoderma gangrenosum.

The ulcers of pyoderma gangrenosum can develop quickly. They usually clear up with treatment, but scarring and recurrences are common.

Symptoms

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.

Causes

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.

Complications

Possible complications of pyoderma gangrenosum include:

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

Prevention

You can't totally prevent pyoderma gangrenosum. If you have the condition, try to avoid injuring your skin. Injury or trauma to your skin, including from surgery, can provoke new ulcers to form. It may also help to control any underlying condition that may be causing the ulcers.