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.

The exact causes of pyoderma gangrenosum are unknown, but it appears to be a disorder of the immune system. People who have certain underlying conditions, such as inflammatory bowel disease or arthritis, are at higher risk of pyoderma gangrenosum.

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

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.

The exact cause of pyoderma gangrenosum is unknown. The condition is not infectious or contagious. It's often associated with autoimmune diseases such as ulcerative colitis, Crohn's disease and arthritis. And 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.

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

• Your age and sex. The condition can affect anyone at any age, though it's more common between 20 and 50 years of 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 arthritis. People with rheumatoid arthritis are at increased risk of pyoderma gangrenosum.
• Having a blood disorder. People with acute myelogenous leukemia, myelodysplasia or a myeloproliferative disorder are at increased risk of pyoderma gangrenosum.

Possible complications of pyoderma gangrenosum include infection, scarring, uncontrolled pain, depression and loss of mobility.

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.

Your doctor will talk with you about your medical history and conduct a physical exam. No test can confirm a diagnosis of pyoderma gangrenosum. But your doctor may order a variety of tests to rule out other conditions that may have similar signs or symptoms. These may include blood tests, a skin biopsy and other tests.

Your doctor may refer you to a specialist in skin conditions (dermatologist).

Treatment of pyoderma gangrenosum is aimed at reducing inflammation, controlling pain, promoting wound healing and controlling any underlying disease. Your treatment will depend on several factors, including your health and the number, size, depth and growth rate of your skin ulcers.

Some people respond well to treatment with a combination of pills, creams or injections. Others may need a stay in the hospital or burn treatment center for specialized wound care. Even after successful treatment, it's common for new wounds to develop.

Medications

• Corticosteroids. The most common treatment are daily doses of corticosteroids. These drugs may be applied to the skin, injected into the wound or taken by mouth (prednisone). Using corticosteroids for a long time or in high doses may cause serious side effects. Because of this your doctor may prescribe steroid-sparing (nonsteroidal) drugs if you need long-term treatment.
• Steroid-sparing drugs. An effective nonsteroidal drug is cyclosporine. Other options include mycophenolate (Cellcept), immunoglobulins, dapsone, infliximab (Remicade) and tacrolimus (Protopic), which is a calcineurin inhibitor. Depending on the type of drug used, it may be applied to the wounds, injected or taken by mouth.
• Pain medication. Depending on the extent of your wounds, you may benefit from pain medication, especially when dressings are being changed.

Wound care

In addition to applying medicine directly to your wounds, your doctor or wound care specialist will cover them with a nonadherent, moist (not wet or dry) dressing and, perhaps, an elasticized wrap. You may be asked to keep the affected area elevated.

Follow your doctor's instructions regarding wound care. This is especially important because many of the oral medications prescribed for pyoderma gangrenosum suppress your immune system, which increases your risk of infection.

Surgery

Because pyoderma gangrenosum can be made worse by cuts to the skin, surgery to remove dead tissue is not usually considered a good treatment option. Trauma to the skin may worsen existing ulcers or trigger new ones.

If the ulcers on your skin are large and need help with healing, your doctor might suggest a skin graft. In this procedure, the surgeon attaches a piece of skin or synthetic skin over the open sores. This is attempted only after the wound inflammation has gone and the ulcer has started healing.

With treatment you're likely to recover from pyoderma gangrenosum. You may feel depressed if the process takes a long time and is painful. Or you may feel stressed about the possibility of recurrence or about how your skin looks. You may find it helpful to talk with a counselor, medical social worker or other people who have or had pyoderma gangrenosum.

If you want counseling or support, ask your doctor for a referral to a mental health professional or contact information for a support group in your area.

You may start by seeing your primary care physician. Or you may be referred immediately to a doctor who specializes in skin conditions (dermatologist).

What you can do

Before your appointment, you may want to write down answers to questions your doctor is likely to ask, such as:

• When did your symptoms begin?
• Have you had similar symptoms in the past? If so, what treatment worked then?
• Have you tried any treatments on your wound? Have they helped?
• What medications and supplements do you take regularly?
• Did you have any damage to your skin, such as a puncture or cut, in the area where the sore developed?
• What other medical conditions do you have?