Pyoderma Gangrenosum

Pyoderma gangrenosum is a rare neutrophilic dermatosis characterized by rapidly enlarging, usually very painful skin ulcers. The words “pyoderma” and “gangrenosum” in its name can be misleading, because this condition is typically not a bacterial infection and does not mean gangrene. The core problem is tissue destruction in the skin resulting from a dysregulated inflammatory response of the immune system. Therefore, no matter how dramatic the lesion appears, the approach should not consist only of “giving antibiotics and waiting.” ^[1][2][3]

The disease often begins as a small pustule, red bump, nodule, or blood-blister-like lesion. Over the course of days, it may progress into a deep ulcer involving the surrounding tissue, with purplish-blue undermined borders and marked tenderness. Although it is commonly seen on the legs, the trunk, around a stoma, a surgical incision line, or other skin areas may also be affected. Sometimes there is a single ulcer, and sometimes multiple ulcers develop. The severity of pain, as much as the appearance of the lesion, is an important diagnostic clue. ^[1][2][4]

What causes pyoderma gangrenosum?

The exact cause of pyoderma gangrenosum has not been fully clarified, but current knowledge places it among immune-mediated diseases with autoinflammatory features. Abnormal activation and tissue-directed migration of neutrophils play an important role in the process. In some patients, no obvious underlying cause is found, whereas in others conditions such as inflammatory bowel disease, inflammatory arthritis, certain hematologic disorders, or more rarely malignancies and drug triggers may be identified. For this reason, pyoderma gangrenosum is usually not assessed as a problem limited only to the skin ulcer. ^[1][2][3][5]

The tendency to worsen after trauma, known as pathergy, is one of the most striking features of this disease. Even a simple needle puncture, a small scratch, a surgical incision, or mechanical irritation around a stoma may trigger the onset or enlargement of the ulcer in some patients. For this reason, if it is mistakenly assumed to be an infection or necrotic wound and extensive surgical debridement is performed, the lesion may enlarge further during the active phase. In pyoderma gangrenosum, the idea that “the more aggressively the wound is cleaned, the better” is generally incorrect. ^[1][4][6]

Symptoms and clinical appearance

The main symptom of pyoderma gangrenosum is a rapidly progressive and markedly painful ulcer. There may be purplish or violaceous discoloration at the borders, surrounding tenderness, drainage from the ulcer base, and at times a pus-like appearance. However, this pus-like appearance does not always mean a bacterial infection. Some patients may also have systemic inflammatory signs such as fever, muscle and joint pain, and fatigue. Pyoderma gangrenosum should be considered especially when a lesion is very painful, becomes clearly more pronounced over hours to days, and worsens despite standard wound care. ^[1][2][4]

Lesions are most commonly seen on the lower extremities, especially the pretibial area, but the chest, abdomen, buttocks, and skin around a stoma may also be affected. In postoperative cases, the risk of confusion with a wound infection is high. When the disease heals, it may leave cribriform scars resembling perforated or wrinkled paper. This scar pattern can be clinically helpful in recognizing prior lesions. In some patients, the presence of multiple ulcers, at least one of them on the anterior lower leg, is also included among the diagnostic criteria. ^[2][4][5]

How is it diagnosed?

There is no single blood test that definitively confirms pyoderma gangrenosum on its own. Diagnosis is supported by careful evaluation of the clinical appearance, exclusion of mimicking causes—especially infectious and vascular ulcers—and additional investigations such as biopsy in appropriate cases. For this reason, it remains a disease that can be difficult to recognize. Venous ulcers, arterial ulcers, vasculitis, infection, malignant ulceration, and drug-related ulcers must all be considered in the differential diagnosis. ^[1][2][4]

The Delphi consensus criteria developed in 2018 provide clinicians with a more systematic approach. Within this framework, the major criterion is demonstration of neutrophilic infiltrate on biopsy taken from the ulcer edge. Minor criteria include exclusion of infection, pathergy, a history of inflammatory bowel disease or inflammatory arthritis, a papule- or pustule-like lesion that rapidly ulcerates, peripheral erythema with an undermined tender border, multiple ulcers, a typical scar appearance, and reduction in ulcer size within the first month of immunosuppressive treatment. The addition of four or more minor criteria improves diagnostic performance. ^[4][5]

A biopsy is often needed less to say “this is pyoderma gangrenosum” than to rule out other causes. Histopathology may be nonspecific, but neutrophil-predominant inflammation supports the diagnosis. Swabs or cultures may also be useful, yet even if organisms grow in culture, it is important to determine whether this represents a primary cause or secondary colonization. In short, the diagnosis is strengthened by a multidimensional evaluation involving dermatology and, when needed, gastroenterology, rheumatology, hematology, and wound care teams. ^[1][2][4]

How is treatment planned?

The main goals of treatment are to reduce pain, stop ulcer progression, limit the risk of secondary infection, and control any associated underlying disease. In mild and limited cases, potent topical corticosteroids, topical tacrolimus, appropriate dressings, and careful local care may be helpful. In wider, deeper, or rapidly progressive ulcers, systemic treatment is required. In clinical practice, oral corticosteroids and cyclosporine are among the most commonly used first-line systemic options. ^[1][2][6][7]

In resistant, recurrent cases or in those with accompanying systemic disease, biologic agents are being used increasingly often. Anti-TNF agents such as infliximab and adalimumab are among the best-known options; in selected patients, ustekinumab, anakinra, and other targeted therapies may also be considered. However, the most appropriate treatment is determined according to the size and activity of the ulcer, associated diseases, risk of adverse effects, and prior treatment response. There is no single treatment regimen in pyoderma gangrenosum that fits everyone. ^[1][3][6][7]

Why is special caution needed with wound care and surgery?

In pyoderma gangrenosum, wound care is a separate and important component of management. The goal is not to scrape the wound aggressively, but to maintain control while minimizing trauma. Appropriate dressing selection, pain management, control of secretions, and careful planning of compression when needed are important. Extensive surgical debridement is generally not recommended during the active phase, because the ulcer may enlarge because of pathergy. If surgical repair or grafting is considered, it is safer to proceed after disease activity has been suppressed and with careful planning. ^[1][4][6]

When should a doctor be consulted?

If there is a rapidly enlarging, very painful skin ulcer with purplish borders or one that worsens despite standard wound care, dermatologic evaluation should not be delayed. Pyoderma gangrenosum should be kept in mind especially if the ulcer develops at a postoperative incision, around a stoma, or at the site of minor trauma. Evaluation becomes even more important if there is fever, widespread pain, rapid enlargement, tenderness severe enough to impair daily function, or a history of inflammatory bowel disease, rheumatologic disease, or hematologic disorder. ^[1][2][4]

Although pyoderma gangrenosum is rare, it can cause severe pain, scarring, and a marked decline in quality of life. The correct approach is a multidisciplinary one that is planned without confusing it with infection, while still ruling out infection; without looking only at the wound, but also investigating associated diseases. Self-starting antibiotics or aggressively cleaning the wound at home is not appropriate. Individual evaluation and specialist follow-up are decisive both for accurate diagnosis and for preventing unnecessary tissue damage. ^[1][2][3][6]

FAQ

Is pyoderma gangrenosum contagious?

No. Pyoderma gangrenosum is not typically a contagious skin disease and does not spread from person to person. Although its appearance may suggest infection, the underlying mechanism is usually immune-mediated inflammation. ^[1][2]

Is every painful leg ulcer pyoderma gangrenosum?

No. Venous ulcers, arterial ulcers, vasculitis, infection, and some skin cancers can mimic pyoderma gangrenosum. For this reason, diagnosis is not made merely by looking at a photo; it is based on examination, culture, biopsy, and differential diagnostic evaluation. ^[2][4][5]

Why is surgical cleaning not always recommended in pyoderma gangrenosum?

Because during the active phase of the disease, trauma may trigger a pathergy response that causes the ulcer to expand. For this reason, extensive debridement is considered cautiously in most cases, and surgical options are usually addressed only after active inflammation has been brought under control. ^[4][6]

Which diseases can it be associated with?

Inflammatory bowel disease, rheumatoid arthritis, and certain hematologic disorders are among the conditions most commonly associated with it. However, in some patients no underlying associated disease may be identified. ^[1][2][3]

How long does treatment take?

Treatment duration varies according to the extent of the ulcer, associated diseases, and the selected therapy. Healing may take weeks or even months, and most patients require regular follow-up and gradual treatment adjustments. ^[1][2][6]