Pyoderma gangrenosum is a rare skin condition that causes painful ulcers. It's usually treatable, but may take some time to heal and may leave some scarring. 

It usually suddenly starts as a small pimple, red bump or blood blister. The skin then breaks down into a painful ulcer with a purple or blue edge, which may ooze fluid.

The ulcer can rapidly get bigger and deeper, and several may develop in the area.

If the ulcer gets infected, you may also feel unwell and develop a high temperature (fever).

Pyoderma gangrenosum usually affects the legs, although it can affect any area of skin, including around the head and neck, arms and genitals. Occasionally, it develops around the site of an injury or surgical wound (see what causes pyoderma gangrenosum? below). 

Despite the similar-sounding name, pyoderma gangrenosum is not related to gangrene.

When to seek medical advice

You should seek medical advice as soon as possible if you think you may have developed pyoderma gangrenosum. Either see your GP or contact your care team if you have one of the conditions mentioned below.

Pyoderma gangrenosum is a serious condition that can progress quickly, so it's important for it to be diagnosed and treated promptly. Early treatment can also help reduce the risk of scarring.

Who is affected

Pyoderma gangrenosum is seen in men and women of any age, but usually affects young and middle-aged adults.

People with the following health conditions are particularly susceptible:

The severity of these conditions is often not related to your chances of developing pyoderma gangrenosum. It can sometimes develop even if the condition is mild or well controlled.

What causes pyoderma gangrenosum? 

The exact cause of pyoderma gangrenosum is not understood, but it's thought to be a reaction to a disease or illness, such as the health conditions listed above.

However, about half of all people with pyoderma gangrenosum have none of these conditions, and there is no obvious reason for it.

There is usually a high concentration of neutrophils (white blood cells involved in inflammation) in the affected tissue, which suggests it may be related to overactivity of the immune system. 

The reaction may sometimes be triggered by minor skin damage or an injury for example, it may develop around the site of a stoma or surgical wound, a needle prick, a biopsy or an insect bite

The skin reaction is not hereditary, so it's not passed from parents to their children. It's also not contagious, so can't be transferred from or to another person.

Diagnosing pyoderma gangrenosum

There is no specific blood test for pyoderma gangrenosum.

If your doctor thinks you might have the condition, they may take a sample of your skin (a biopsy) to examine under the microscope in a laboratory. This can help rule out other causes of skin ulcers.

Your doctor may also take a swab of the wound to check for any infection, and may order blood tests to check for conditions that are associated with pyoderma gangrenosum.

How pyoderma gangrenosum is treated

Pyoderma gangrenosum is treatable, but may take some time to heal. There’s no clear evidence to suggest what the best treatment is, but the main treatments are outlined below.

Care of the wound

Dressings may need to be applied regularly to soak up any discharge and help retain the creams applied to the wound. Any severely damaged tissue should be gently removed by a doctor or nurse.

Creams, ointments or injections

Strong steroid creams or ointments are applied on and around ulcers daily or on alternate days. They often help the ulcers heal quickly, particularly if they are small and diagnosed early.

Alternatively, the steroid medication triamcinolone may be injected into the edge of the ulcer. In more severe cases, steroid medication may be injected into a vein (intravenously).

Tacrolimus ointment has also proved useful in treating pyoderma gangrenosum ulcers.

Steroid tablets

Most people with pyoderma gangrenosum will need to take steroid tablets such as prednisolone, either on their own or with antibiotics such as dapsone or minocycline. These reduce inflammation and help the ulcers to heal.

However, the long-term use of steroids is associated with serious side effects such as bone thinning (osteoporosis), so they need to be used with caution. Read more about the side effects of steroid medication.


Pyoderma gangrenosum is thought to be caused by an overactive immune system, and immunosuppressants (medication that suppresses the immune system) have proved useful in reducing pain and helping the ulcers to heal.

A few examples are ciclosporin, mycophenolate mofetil, and newer treatments such as infliximab, which are used for more severe cases of the condition.

However, immunosuppressants can have unpleasant side effects and will need to be given and monitored by a specialist. They're not currently licensed for the treatment of pyoderma gangrenosum.


In many people with pyoderma gangrenosum, the ulcers heal with relatively simple treatments. However, some scarring in the affected area is common.

The progression of the condition varies from person to person – it may suddenly clear up within a few weeks, stay the same for months or years, or slowly heal over many months.

Some people have flare-ups after the slightest injury or for no apparent reason, and in some cases the condition recurs after treatment.

Page last reviewed: 30/03/2015

Next review due: 27/02/2017