Pyoderma Gangrenosum Phenotype Classification

Area of Science:

• Dermatology
• Internal Medicine

Background:

• Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis presenting as sterile ulcerative skin lesions.
• Existing literature associates PG with various comorbidities and clinical features, yet lacks standardized classification for its phenotypes.

Purpose of the Study:

• To establish an expert-driven classification framework for pyoderma gangrenosum (PG) phenotypes.
• To inform the development of future treatment guidelines and research endeavors for PG.

Main Methods:

• A modified Delphi consensus study involving 23 expert dermatologists.
• Five rounds of anonymous, iterative online surveys conducted between December 2023 and July 2025.
• A literature review summarizing existing data on PG associations and comorbidities preceded the survey rounds.

Main Results:

• Consensus was achieved on a PG classification framework with 83% expert agreement.
• Phenotypes were categorized into PG with autoinflammatory syndromes and nonsyndromic PG.
• Nonsyndromic PG includes inflammatory bowel disease-associated, hematologic cancer-associated, drug-induced, and other (idiopathic) PG. Modifiers include special site involvement and extracutaneous manifestations.

Conclusions:

• An expert-established framework provides standardized classification for distinct PG phenotypes and modifiers.
• This nomenclature is expected to enhance consistency in epidemiological research and reporting of outcomes for PG patients.
• The framework may guide upcoming clinical guidelines for managing pyoderma gangrenosum.