From the Guidelines
Pyoderma gangrenosum is caused by an abnormal immune system response that leads to severe skin inflammation, often triggered by underlying systemic conditions such as inflammatory bowel diseases, autoimmune diseases, or trauma to the skin. It is an autoinflammatory neutrophilic dermatosis where the body's immune system mistakenly attacks healthy skin tissue. The exact trigger is often unknown, but pyoderma gangrenosum frequently occurs in association with underlying systemic conditions, including inflammatory bowel diseases (ulcerative colitis and Crohn's disease), rheumatoid arthritis, hematologic disorders (leukemia, lymphoma, monoclonal gammopathy), and other autoimmune diseases 1. In some cases, trauma or injury to the skin (pathergy) can initiate lesion development, as noted in the context of postsurgical stomas or trauma to the shins 1. Genetic factors may also play a role in susceptibility. At the cellular level, there is dysregulation of neutrophil function and inflammatory cytokines, particularly TNF-alpha, IL-1, and IL-17, which contribute to the characteristic painful, rapidly expanding ulcers with undermined violaceous borders.
Some key points to consider in the diagnosis and understanding of pyoderma gangrenosum include:
- The condition can occur anywhere on the body, including the genitalia, but the most common sites are the shins and adjacent to stomas 1.
- Pyoderma gangrenosum is usually diagnosed clinically, based on the characteristic appearance of the lesions following exclusion of other possible skin diseases 1.
- The therapeutic goal should be rapid healing, as pyoderma gangrenosum can be a debilitating skin disorder 1.
- Treatment focuses on controlling the inflammatory response and addressing any underlying conditions that may be driving the immune dysregulation, with options including systemic corticosteroids, infliximab, adalimumab, or topical or oral calcineurin inhibitors 1.
From the Research
Causes of Pyoderma Gangrenosum
The causes of Pyoderma gangrenosum (PG) are not fully understood, but several factors have been identified as contributing to the development of the disease. These include:
- Underlying systemic diseases, such as inflammatory bowel disease, rheumatological disorders, hematological malignancies, or other autoimmune conditions, which are associated with PG in 50-70% of cases 2, 3, 4, 5
- Immune dysregulation, characterized by the presence of abnormal neutrophils and T-cells, leading to the production of inflammatory mediators such as IL-1β, IL-8, IL-17, and TNF-α 6
- Trauma, which can trigger the onset of PG in 20-30% of patients, a phenomenon known as pathergy 4
- Genetic factors, as PG can occur as part of an inherited inflammatory syndrome 6
- Other potential triggers, such as infections or malignancies, although these are less common 2, 3
Associated Conditions
PG is often associated with other conditions, including: