Pyoderma Gangrenosum: Painful Ulcers, Diagnosis, and Treatment

Pyoderma gangrenosum (PG) is an uncommon inflammatory skin condition that can cause a very painful ulcer to develop and enlarge quickly. It may begin as a small bump, pustule, or blister. The word “gangrenosum” is misleading: PG is not a form of gangrene, is not contagious, and is not itself an infection. A wound that looks like PG still needs prompt medical evaluation because several urgent conditions can look similar.

Medical information: This article is for general education, not diagnosis or personal wound-care instructions. A rapidly growing or very painful ulcer needs prompt medical assessment. Seek emergency care for severe worsening pain, fever with feeling very unwell, confusion, spreading redness, or other signs of serious infection or tissue damage.

What pyoderma gangrenosum is

Pyoderma gangrenosum belongs to a group of inflammatory skin diseases called neutrophilic dermatoses. Neutrophils are white blood cells that help defend the body. In PG, immune inflammation involving neutrophils damages skin and can create an ulcer. The exact cause is not fully understood. It is not caused by a contagious germ, although an open wound can later become infected.

The name dates from an earlier period when the condition was thought to be an infection. Modern patient guidance from the British Association of Dermatologists explains that PG is not a type of gangrene: gangrene occurs when tissue loses its blood supply, which is not what defines PG. The name can cause unnecessary fear, so it helps to understand what the diagnosis actually means.

PG can occur without a known underlying disease. In other people, it is associated with inflammatory bowel disease such as ulcerative colitis or Crohn's disease, inflammatory arthritis, or certain blood disorders. Rarely, other illnesses or medicines may be relevant. Finding an associated condition is part of a careful assessment, but having PG does not automatically mean someone has cancer or bowel disease.

The ulcer may be the most visible part of the condition, but the effects reach beyond the skin. Pain, dressing changes, reduced mobility, sleep disruption, scarring, and concern that another wound may form can interfere with daily life. Care often brings dermatology together with wound-care clinicians and, when relevant, specialists treating bowel, joint, or blood conditions.

How it may look and feel

Classic ulcerative PG often starts with a tender red bump, pustule, or blood-filled blister. The surface may break down into a shallow or deep open sore. The ulcer can grow over days, sometimes with a ragged or irregular border and an overhanging edge. It is often very painful, and pain can seem greater than a person might expect from the wound's size.

The rim may look red, dusky, purple, or blue-violet. In darker skin, the border may look darker than the surrounding area rather than clearly purple. Inflammation around the wound may also alter color. Lighting, skin tone, wound depth, and infection can change how it appears. A photograph or online image comparison cannot confirm PG.

The legs are a common location, particularly the lower legs, but PG can develop elsewhere. It may occur near a stoma, at a surgical incision, or after another skin injury. One ulcer is common, but several may occur, and nearby wounds can merge. Once inflammation settles, the skin may heal with a scar or an area that is lighter, darker, thinner, or uneven compared with the surrounding skin.

PG can also take less familiar forms. Clinicians describe pustular, bullous, vegetative, peristomal, and postsurgical patterns as well as the classic ulcerative form. A pustular pattern may involve small pus-like bumps; bullous PG can begin with blisters; vegetative PG may form a more slowly evolving plaque; peristomal disease appears around an ostomy opening; and postsurgical PG develops at or near an operation site. These labels describe patterns and locations, not different infections.

Not every painful ulcer is PG. Venous disease, reduced arterial blood flow, vasculitis, infection, medication effects, skin cancer, and other inflammatory disorders can cause wounds that resemble it. Some lookalikes are emergencies. The right response to a suspicious ulcer is timely medical assessment, not self-treatment based on an internet photo.

Pathergy: when skin injury can worsen a lesion

Pathergy describes a tendency for skin trauma to trigger or worsen inflammation in some people with PG. A lesion may appear after a scrape, injection, cut, surgery, or other injury. Existing ulcers can also enlarge after manipulation. This is one reason a wound that seems to worsen after a procedure deserves careful review by the treating team.

Pathergy does not occur in every person, and its absence does not rule out PG. It is a clinical clue considered alongside the wound's appearance, history, biopsy, and exclusion of other causes. Clinicians do not need to provoke a new injury to check for it. Deliberately pricking, rubbing, or cutting an area at home is unsafe and can create a wound.

Pathergy also creates a difficult balance: doctors sometimes need a biopsy, culture, or procedure to investigate a dangerous-looking ulcer, yet skin manipulation may worsen PG. A clinician weighs the need to rule out infection, circulation problems, or another cause against that risk, then chooses the least harmful way to get the information needed. Never delay urgent care because you are worried a test might cause irritation; tell the team if PG is already suspected or diagnosed.

Wound care should be gentle and individualized. Follow the care plan for cleansing, dressings, pain control, and movement. Avoid scrubbing or removing tissue yourself. If dressing changes are very painful or the wound expands after a change, tell the wound-care clinician so the technique and materials can be reviewed.

Who may be affected and related health conditions

PG can occur at different ages. Many cases arise in adults, but children and older adults can also be affected. The condition is uncommon, so clinicians may not encounter it often. This unfamiliarity, combined with its resemblance to infection and vascular ulcers, can make diagnosis challenging.

Inflammatory bowel disease and inflammatory arthritis are among the better-known associated conditions. Some blood disorders, including certain marrow or blood-cell diseases, may also be linked. A person can have one of these conditions before PG appears, learn about it during the ulcer workup, or have no related diagnosis at all. The association is a reason to ask a few focused questions, not to assume the condition is present.

During an appointment, clinicians may ask about ongoing diarrhea, blood in the stool, abdominal pain, joint swelling or stiffness, unusual fatigue, easy bruising, or prior blood test abnormalities. Testing is guided by history and examination; people do not need every possible screening test. If a related condition is known, coordinating treatment can help the clinicians make a plan that considers both the ulcer and the rest of the person's health.

PG is not inherited in the usual sense and is not passed from parent to child. Rare inflammatory syndromes can include PG-like skin disease, especially when symptoms start early in life or appear with other unusual inflammatory problems. A specialist may consider these uncommon possibilities when the history suggests them.

How clinicians diagnose pyoderma gangrenosum

There is no single blood test, culture, or biopsy result that proves PG. Diagnosis is made from the whole clinical picture, while other causes of ulceration are investigated. The clinician asks how the wound began, how quickly it changed, how much it hurts, whether there was a recent injury or procedure, and whether similar wounds occurred before. They examine the border, surrounding skin, location, and signs of infection or impaired circulation.

Tests are chosen to answer specific questions. A swab or tissue sample may be used to look for infection. Blood tests may check for inflammation, anemia, or other clues. Depending on the wound and medical history, clinicians may assess blood flow, check for vasculitis or medication effects, or evaluate for a related bowel, joint, or blood condition.

A skin biopsy may show many neutrophils, but that finding is not unique to PG. One purpose of a biopsy is to help exclude other diagnoses, including infection, vasculitis, or cancer. The decision about a biopsy depends on how much information is needed and the possibility of pathergy. A clinician may collect tissue from the active ulcer edge or use another strategy; the exact approach belongs to the medical team.

Specialists sometimes use published clinical criteria to organize the evidence. The Delphi criteria for ulcerative PG include a major biopsy feature plus a combination of additional clues, such as exclusion of infection, pathergy, a history of inflammatory bowel disease or arthritis, a rapidly ulcerating starting lesion, a characteristic border, certain scars, or improvement with immune-directed treatment. These are tools for clinicians, not a checklist for self-diagnosis.

The diagnostic process may take more than one visit, especially if wound cultures or other tests take time. Some mimics need very different treatment: for example, infection may call for antimicrobial therapy, while poor circulation requires a different evaluation. A suspected PG diagnosis should remain open to revision if the wound or test results do not fit. Mayo Clinic summarizes this principle in its diagnosis and treatment overview.

Treatment and wound care

The goal of treatment is to control inflammation, relieve pain, protect the wound, support healing, and reduce the chance of new ulcers. The plan depends on how quickly the ulcer is expanding, how many areas are affected, the depth and location, other health conditions, and the risks of treatment. Dermatologists often coordinate with a wound-care team and the clinician treating any associated illness.

For limited disease, a clinician may consider prescription anti-inflammatory creams or ointments applied to the skin. More extensive, rapidly progressive, or difficult disease may require oral or injected medicines that reduce inflammation or modify immune activity. Examples used in specialist care include corticosteroids, ciclosporin, other steroid-sparing medicines, or biologic therapies. Choice of medicine is individualized; these treatments can have significant side effects and may require laboratory or other monitoring.

PG can take weeks or months to settle. Some patients need more than one treatment over time. A medicine used for a short period to control a flare may differ from a longer-term option used to prevent recurrence. Do not stop systemic steroids or immune-suppressing medicine suddenly unless the prescriber tells you to. Ask how long a medicine is expected to be used, what monitoring is needed, and which symptoms should be reported right away.

Wound care aims to keep the ulcer protected while avoiding unnecessary trauma. A clinician may select a non-stick dressing, moisture balance, protective padding, or a wrap depending on drainage, location, swelling, and surrounding skin. Dressing changes should be as gentle as practical. Pain management is part of wound care, not an afterthought; ask for a plan before a painful dressing change, especially if the wound is large or sensitive.

Because PG can worsen with injury, aggressive debridement during active disease is generally approached with caution. At the same time, a clinician must be able to investigate and treat a true infection or another emergency. Decisions about removing tissue, compression, grafting, or surgery should be made by clinicians who understand the diagnosis and have reviewed the wound. Selected reconstructive procedures may be considered in carefully managed situations after inflammation is controlled; surgery is not a do-it-yourself or routine first step.

Associated conditions need their own treatment plan. Controlling bowel or joint inflammation may be important for overall health, and certain medicines may address both an associated condition and PG. The care team should review all current medicines and allergies, including treatments from other specialists, before changing therapy.

When to seek care

Arrange prompt medical assessment for a new ulcer that is growing quickly, becoming very painful, or appearing after an injury or operation. Tell the clinician if PG is known or suspected, especially before a procedure. Early evaluation can help distinguish PG from infection, circulation problems, and other conditions that need different treatment.

Get emergency care for severe or rapidly worsening pain, fever or chills with feeling very unwell, confusion, fast-spreading redness or swelling, blackening tissue, or sudden weakness. These signs can occur with serious infection or other urgent illness and cannot be safely sorted out at home. The fact that PG itself is inflammatory does not mean that every ulcer is sterile or that infection can be dismissed.

For a person already being treated for PG, contact the care team if the ulcer is enlarging, new ulcers appear, drainage changes, dressing changes become harder, pain increases, or medicine side effects develop. Do not change medication or wound care on your own while waiting for advice unless the emergency plan says to seek immediate care.

Living with pyoderma gangrenosum

A chronic wound can make routine activities difficult. Ask the care team about protecting the area during bathing, work, sleep, or movement; managing odor or drainage; choosing clothing that does not rub; and arranging supplies. The right approach may change with the wound's location and the stage of healing. A wound-care nurse can demonstrate dressing changes and help adapt them to a person's home setup.

Take progress photos only if the clinician finds them useful, and keep them private. Use similar lighting and distance so changes are easier to compare. Notes can include wound size if the care team has shown how to measure it, pain, drainage, temperature, medicine changes, and any new symptoms. Do not press, probe, or scrape an ulcer to collect information.

Recovery can be uneven. A wound may improve slowly, flare, or leave a scar. People may feel anxious about new lesions or frustrated by repeated appointments. Ask about mental health support, peer support, or help with work and daily activities. A clinician can also provide a concise summary for emergency or surgical teams so the diagnosis and pathergy risk are clear.

Preparing for an appointment

Bring a list of current medicines, allergies, prior skin problems, and any diagnosis of inflammatory bowel disease, arthritis, or a blood disorder. Explain when the wound began, how quickly it changed, how painful it is, whether a recent procedure or injury preceded it, and what care has already been tried. If possible, bring a timeline or clinician-approved photos that show changes over several days.

Useful questions include: What conditions could mimic PG in my case? Is a culture or biopsy needed? How will we balance diagnostic tests with pathergy risk? What is the wound-care plan? Which symptoms mean I should seek emergency care? What side effects or laboratory monitoring apply to the treatment? Should another specialist assess possible associated disease?

If a procedure is planned, make sure the procedural team knows the full wound history and whether PG has been considered. This is particularly relevant when ulcers appear after surgery or near an ostomy. Sharing the information supports a coordinated decision about diagnosis, infection risk, wound handling, and the safest treatment.

Common misconceptions

“The name means it is gangrene.” It does not. The word is historical. PG is an inflammatory neutrophilic skin disease, not loss of blood supply by definition.

“The pus means the wound must be infected.” Inflammation can produce drainage that looks like pus. A wound can also become secondarily infected, so clinicians assess it rather than deciding from drainage alone.

“It is contagious.” PG does not spread from person to person. Normal wound hygiene still matters because any open skin can be vulnerable to infection.

“A biopsy always confirms PG.” Biopsy can help rule out other causes and may show neutrophils, but there is no specific biopsy pattern that independently confirms the diagnosis.

“All wound procedures are forbidden.” Procedures need careful planning because trauma can worsen PG, but clinicians may still need samples or treatment. In selected cases, surgical reconstruction may be considered with disease control and specialist guidance.

Frequently asked questions

Sources and further reading

• British Association of Dermatologists. Pyoderma gangrenosum patient information leaflet, updated October 2025.
• Mayo Clinic. Pyoderma gangrenosum: symptoms and causes.
• Mayo Clinic. Pyoderma gangrenosum: diagnosis and treatment.
• Park AN et al. Narrative Review: Pyoderma Gangrenosum. 2024.
• Maverakis E et al. Diagnostic Criteria of Ulcerative Pyoderma Gangrenosum: A Delphi Consensus of International Experts. JAMA Dermatology. 2018.
• Ormerod AD et al. STOP GAP randomized controlled trial of prednisolone versus ciclosporin. BMJ. 2015.

Editorial note: This article is intended for general education. It cannot diagnose an ulcer or replace wound assessment and treatment from qualified healthcare professionals.