Pyoderma gangrenosum (PG) is an inflammatory, noninfectious, ulcerative neutrophilic skin disease of uncertain etiology commonly misdiagnosed as an aggressive skin infection. Pustules form and give way to ulcers with a necrotic, undermined margin. PG can affect any age, but is rare in the pediatric population. It may take on a number of differing clinical presentations. PG can have either an acute or chronic course and result in extensive scarring (which can be keloidal or have dyspigmentation, especially in patients with darker skin types). There is no predilection for sex or any population. The disease occurs most often in middle-aged adults.

The two primary variants are a classic ulcerative form, which often involves the lower extremities, and a vesicobullous form, which is more superficial and tends to occur on the upper extremities, including hands. Fever, toxicity, and pain can be associated with the onset of PG. Extracutaneous manifestations may take the form of sterile neutrophilic abscesses, such as in the lungs, heart, gastrointestinal tract, liver, eyes, central nervous system, and lymphatic tissue.

Although the exact cause is unknown, neutrophil dysfunction, inflammation, and genetics are all thought to play a role. Additionally, PG has associations with a number of systemic illnesses. In the majority of pediatric cases, there is an association with ulcerative colitis or Crohn disease, but other associations in this population include inherited and acquired immunodeficiencies, leukemia and other hematologic disorders, and a range of rheumatologic disorders including juvenile idiopathic arthritis and systemic lupus erythematosus. For genetic conditions, see Look For.

PG tends to be self-limited. First-line therapies are widely accepted, while alternative therapeutic recommendations are largely based on anecdotal evidence. Surgical intervention is a common exacerbating factor because PG demonstrates pathergy, a phenomenon by which skin trauma can lead to worsening disease.