Pyoderma gangrenosum

In about half of people with PG there is no known cause. In some cases, it may start after damage to the skin. In other cases, people may have an underlying medical condition (for example, inflammatory bowel disease, arthritis, or certain blood disorders).

Rarely, PG can be linked with underlying cancers or can be triggered by medications. However, people with PG do not always have another condition. Your healthcare professional will do checks to rule out these conditions.

What does pyoderma gangrenosum look and feel like?

PG can look different from person to person. It may start as a small pimple, red bump, pustule or blood-blister. The skin usually breaks down to form a painful ulcer that can get larger very quickly.

The edge of the ulcer may appear purple in colour in white skin tones. In brown or black skin, the colour may appear darker than the surrounding skin.

After the ulcer heals, a scar may form. This scar might look different from the surrounding skin – it could be darker, lighter, thinner, wrinkled, or have small dents.

PG most commonly appears on the legs, but it can also affect other parts of the skin. Sometimes it develops around a stoma (such as colostomy), or in a surgical wound.

There is usually a single large ulcer. Occasionally, there may be multiple ulcers. Ulcers may become infected, oozing fluid or pus. It is common for the ulcer to cause discomfort or pain.

PG does not usually come back, but it can, especially if the underlying health problem that caused it is not fully controlled.

There is no single test that can confirm PG. Instead, the diagnosis is based on:

• examining the skin (clinical assessment),
• ruling out other causes of skin ulcers,
• different tests to check for related conditions.

Your healthcare professional will need to rule out other possible conditions that can look like PG. These can include:

• venous ulcers,
• inflammation of blood vessels,
• skin infection or injury,
• cancer.

They may take a swab of the skin to check there is no infection.  You may also be asked to give blood, urine and stool samples to check that you don't have other conditions that can be linked with PG.

Your healthcare professional may need to take a small sample of skin (biopsy) to be examined under the microscope in a laboratory. This test is helpful in ruling out other causes of skin ulceration. PG does not have a specific appearance under the microscope, but there can be many white blood cells (called neutrophils) in the area.

PG is not hereditary and is not passed from parent to child.

PG is often difficult to treat and may take some time to heal. You will remain under follow up until the condition is controlled. More than one treatment may need to be tried. Skin grafts and surgery are not treatment options as they often fail and may cause the ulcer to become bigger.