Pyoderma Gangrenosum: Complete Guide to the Rapid, Painful Skin Condition
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026
TL;DR
Pyoderma gangrenosum is a rare skin condition that starts as a small bump — sometimes mistaken for a spider bite — and can become a large, painful open sore within days. It is not an infection and is not contagious. Most people have it alongside autoimmune conditions like ulcerative colitis, Crohn's disease, or arthritis. Diagnosis is by exclusion since no test can confirm it, and treatment relies on corticosteroids and other immune-targeting medicines combined with careful wound care. With treatment, people usually recover, though sores can take weeks or months to heal.
Quick answer: Pyoderma gangrenosum is a rare immune-related skin disorder that causes large, painful sores that develop quickly, most often on the legs. It is not contagious and not caused by infection. It most commonly affects women aged 20 to 50 and is strongly linked to inflammatory bowel disease and rheumatoid arthritis. Diagnosis requires ruling out similar conditions, often with a dermatologist's help. Treatment combines corticosteroids or immune-system medicines with gentle wound care — surgery to remove tissue is usually avoided because it can make the condition worse. Healing takes weeks to months, and the condition typically clears up with treatment, though scars and new sores are common.
What Is Pyoderma Gangrenosum?
Pyoderma gangrenosum is a rare condition that causes large, painful sores on the skin. The name is pronounced pie-o-DUR-muh gang-ruh-NO-sum.
The sores can develop remarkably fast. Most often they appear on the legs, though they may form anywhere on the body, sometimes around surgical sites.
The exact causes are unknown, but it appears to be a disorder of the immune system. People who have certain other conditions are at higher risk.
The condition usually clears up with treatment. However, the sores often leave scars and can show up in new spots. Advanced sores characteristically have blue or purple edges.
How Pyoderma Gangrenosum Sores Develop
Three-stage progression of pyoderma gangrenosum: a small bump that may look like a spider bite, rapid growth into a large painful sore within days, and merging of two or more sores into one.
Pyoderma gangrenosum usually begins with a small bump on the skin. It might look like a spider bite, which is how many people first explain it.
Within days, that bump can turn into a large and painful open sore. The speed of this change is one of the condition's defining features.
The sore usually appears on the legs but may develop anywhere on the body. It sometimes appears around surgical sites.
If you have two or more sores, they may grow and merge into one larger sore.
Symptoms to Watch For
The key symptom is a painful, rapidly growing skin wound. That single red flag is worth acting on immediately.
Beyond the visible sore, the condition carries risks of complications as it progresses.
Small starting bump: Appears quickly; may look like a spider bite
Rapidly growing sore: A large, painful open sore forms within days
Typical location: Most often on the legs, but can occur anywhere
Blue or purple edges: Characteristic of advanced-stage sores
Merging sores: Two or more sores may grow and merge into one
Surgical-site appearance: Sores sometimes form around surgical wounds
Possible complications include the following:
Infection: Open sores create a route for infection
Uncontrolled pain: Pain can become difficult to manage
Scarring: Sores often leave scars as they heal
Skin darkening: Postinflammatory hyperpigmentation — skin darkens after healing
Skin lightening: Postinflammatory hypopigmentation — skin loses color after healing
People with brown or Black skin have a higher risk of long-term skin color changes after the sores heal.
When to See a Doctor
Talk with a health care professional if you develop a painful, rapidly growing skin wound.
Early diagnosis matters because correct and early diagnosis is key to effective treatment. Do not wait for the sore to spread.
Causes and What We Know
No one knows the exact cause of pyoderma gangrenosum. It is not an infection, and it is not contagious.
The condition appears to be a disorder of the immune system. It is often seen in people who have autoimmune diseases such as ulcerative colitis, Crohn's disease, and arthritis.
Some studies suggest that it may be passed down through families, pointing to a possible genetic component.
A critical feature of this condition is its response to skin injury. If you have pyoderma gangrenosum, getting a cut or other skin wound can bring on new sores.
Who Is at Risk
Sex and age: Being a woman between 20 and 50 years of age
Inflammatory bowel disease: Ulcerative colitis or Crohn's disease
Autoimmune joint disease: Rheumatoid arthritis
Blood disorders: Acute myelogenous leukemia or myelodysplasia
The exact cause of pyoderma gangrenosum is unknown, but it is linked to ulcerative colitis, Crohn's disease, rheumatoid arthritis, and blood disorders, with skin injury able to trigger new sores.
Prevention
You cannot prevent the first instance of pyoderma gangrenosum.
If you have the condition, you can help prevent new sores by protecting your skin from injury. Injury or trauma to the skin, including from surgery, can cause new sores to form.
It also may help to control any other condition you have that is related to pyoderma gangrenosum, such as inflammatory bowel disease or rheumatoid arthritis.
How Is Pyoderma Gangrenosum Diagnosed?
No test can confirm a diagnosis of pyoderma gangrenosum. This is unusual and important to understand: diagnosis happens by ruling other conditions out.
Your health care professional will talk with you about your symptoms and medical history and conduct a physical exam.
You may need tests to rule out conditions that have similar symptoms.
Medical history and physical exam: Establishes symptoms, speed of onset, and skin findings
Blood tests: Rules out other conditions with similar symptoms
Chest X-ray: Rules out other conditions with similar symptoms
Colon exam: Checks for related inflammatory bowel disease
Skin biopsy: Tissue sample tested in a lab to rule out other conditions
Correct and early diagnosis is key to effective treatment. You may be referred to a specialist in skin conditions — a doctor called a dermatologist.
Treatment Options
Treatment of pyoderma gangrenosum is aimed at reducing swelling, controlling pain, and helping skin sores heal.
Medicines are the most common treatment. Treatment might also involve wound care and surgery, though surgery is approached with caution for reasons explained below.
Your treatment depends on your health, how many sores you have, how deep they are, and how fast they are growing.
Some people respond well to treatment with a combination of medicine taken by mouth, creams, and injections.
Treatment combines corticosteroids and steroid-sparing immune-system medicines with careful wound care; surgery is used with caution since skin trauma can worsen sores.
Corticosteroids
The most common treatment for pyoderma gangrenosum is daily doses of corticosteroids. These drugs may be applied to the skin, injected into the wound, or taken by mouth. The pill form is called prednisone.
Using corticosteroids for a long time or in high doses may cause severe side effects. To avoid these side effects, steroids may be used only for short periods of time to control the sores. Other medicines that target the immune system may then be used long term to control the disease.
Medicines That Target the Immune System
Some medicines can stop your immune system from attacking healthy tissues. These are called steroid-sparing medicines or steroid-sparing drugs.
Examples include cyclosporine, mycophenolate, immunoglobulins, dapsone, infliximab, and tacrolimus. Tacrolimus is a type of medicine called a calcineurin inhibitor.
Steroid-sparing medicines might be applied to the wounds, injected, or taken by mouth. These medicines also can have severe side effects.
Pain Medicine
Depending on the extent of your wounds, you may benefit from pain medicine, especially when your dressings are being changed.
Wound Care
In addition to applying medicine to your wounds, a health care professional may cover them with a moist nonstick dressing and, perhaps, an elasticized wrap. You may be asked to keep the affected area raised.
Follow instructions you receive for wound care carefully.
Surgery — Used With Caution
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 sores or bring on new ones.
If sores are large and are not healing, a skin graft may be an option. In this procedure, the surgeon attaches a piece of skin from somewhere else on your body over the open sores.
Corticosteroids: Most common treatment; applied, injected, or taken by mouth; usually short term
Immune-system medicines: Steroid-sparing drugs for long-term control; applied, injected, or taken by mouth
Pain medicine: Helpful depending on wound extent, especially during dressing changes
Wound care: Moist nonstick dressing, elasticized wrap, keep the area raised
Surgery: Usually avoided; skin graft considered for large sores that will not heal
Healing Timeline and Outlook
With treatment, you are likely to recover from pyoderma gangrenosum. That said, healing is slow.
Sores can take weeks or months to heal. It is common for new sores to develop along the way. The sores often leave scars and can show up in new spots.
It is normal to feel stressed about whether new sores will form. You may find it helpful to talk with a counselor, a medical social worker, or other people who have or had pyoderma gangrenosum. You may want to connect with a support group in person or online. Ask your health care professional for suggestions.
How to Prepare for Your Appointment
You are likely to first see your regular health care professional. You may then be referred to a dermatologist — a doctor who specializes in skin conditions.
Before your appointment, make a list of your symptoms and how long you have been having them, key personal information including any major stresses or recent life changes, all medicines, vitamins and supplements you take including doses, and questions to ask your health care professional.
Your doctor is likely to ask when you first began experiencing symptoms, whether anything seems to improve your symptoms, what steps you have taken to treat the condition yourself, whether any of those measures helped, whether you have ever been treated by a health care professional for this condition, whether you used any prescription treatments and the name and dosage if so, and whether you have ever had a skin biopsy.
Living Well After Diagnosis
Protecting your skin from injury is the single most effective daily habit for preventing new sores. Plan ahead for any planned surgeries and discuss your condition with the surgical team in advance.
Controlling any related condition — such as inflammatory bowel disease or rheumatoid arthritis — may also help keep pyoderma gangrenosum in check.
Follow your wound care instructions consistently. Healing is measured in weeks and months, so patience and persistence with the treatment plan matter.
Conclusion
Pyoderma gangrenosum can be frightening because of how fast its sores develop — a small bump that looks like a spider bite can become a large, painful wound within days. But the outlook is encouraging: it is not an infection, it is not contagious, and with treatment people usually recover.
The most important step is acting quickly. If you have a painful, rapidly growing skin wound — especially if you have ulcerative colitis, Crohn's disease, or rheumatoid arthritis — contact a health care professional right away. Correct and early diagnosis is key to effective treatment.
Talk to a dermatologist this week if you suspect pyoderma gangrenosum. Bring a list of your symptoms, how long you have had them, and every medicine or supplement you take.
Frequently Asked Questions
1. What is pyoderma gangrenosum?
Pyoderma gangrenosum is a rare condition that causes large, painful sores on the skin. It appears to be a disorder of the immune system. Sores develop quickly — a small bump can become a large open sore within days — and most often appear on the legs. It usually clears up with treatment, though sores often leave scars and can recur in new spots.
2. Is pyoderma gangrenosum contagious?
No. Pyoderma gangrenosum is not an infection and it is not contagious. It appears to be an immune system disorder in which the body's defenses mistakenly attack the skin.
3. What does pyoderma gangrenosum look like?
It usually starts as a small bump on the skin that might look like a spider bite. Within days it can turn into a large, painful open sore, often with blue or purple edges in its advanced stage. It most often appears on the legs but can develop anywhere on the body, sometimes around surgical sites. If you have multiple sores, they may grow and merge into one.
4. What causes pyoderma gangrenosum?
No one knows the exact cause. It appears to be an immune system disorder and is often seen in people with autoimmune diseases such as ulcerative colitis, Crohn's disease, and arthritis. Some studies suggest it may be passed down through families. Notably, a cut or other skin wound — including surgery — can trigger new sores.
5. Who is most likely to get pyoderma gangrenosum?
Women between 20 and 50 years of age are at higher risk, along with people who have inflammatory bowel disease (ulcerative colitis or Crohn's disease), rheumatoid arthritis, or certain blood disorders such as acute myelogenous leukemia or myelodysplasia.
6. How is pyoderma gangrenosum diagnosed?
No test can confirm a diagnosis of pyoderma gangrenosum. Instead, a health care professional takes a medical history, performs a physical exam, and orders tests — blood tests, a chest X-ray, a colon exam, or a skin biopsy — to rule out other conditions with similar symptoms. Referral to a dermatologist is common, and correct, early diagnosis is key to effective treatment.
7. What is the treatment for pyoderma gangrenosum?
Treatment aims to reduce swelling, control pain, and help sores heal. Medicines are the most common treatment: daily corticosteroids (applied, injected into the wound, or taken by mouth) are the first line, with steroid-sparing immune-system medicines for long-term control, plus pain medicine as needed. Careful wound care with moist nonstick dressings is standard. Surgery to remove dead tissue is usually avoided because skin trauma can worsen or trigger sores; a skin graft may be considered for large sores that will not heal.
8. How long does it take for pyoderma gangrenosum to heal?
Sores can take weeks or months to heal, and it is common for new sores to develop along the way. With treatment, people are likely to recover, though sores often leave scars and can recur in new spots.
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Medical Disclaimer
This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified health care provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read here.
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