Overview: What is Pyoderma Gangrenosum?

The CSPA gratefully acknowledges  Khalad Maliyar, fourth-year medical student at the University of Toronto, Faculty of Medicine, and Kirk Barber, MD, FRCPC for assistance in the preparation of this report. June 2021.

Pyoderma gangrenosum (PG) is an uncommon, recurring skin disorder that leads to painful open sores, also known as ulcers, on the body. 


PG can affect individuals of any age but tends to occur more commonly between the ages of 40 and 60. It affects females more than males. Approximately 4% of all individuals with PG are infants and children.  

Connections with other conditions:

Approximately half of all patients with PG have an underlying systemic condition. The most common conditions associated with PG include inflammatory bowel disease (i.e., ulcerative colitis and Crohn’s disease), arthritis, and blood disorders (e.g., multiple myeloma, leukemia, monoclonal gammopathy).  


Since PG  frequently occurs with many medical conditions, it is believed to be caused by an abnormality in the immune system.  

Fast Facts:

  • The incidence of PG is approximately 3-10 cases per million people/year.
  • PG is commonly associated with systemic disorders including inflammatory bowel disease (IBD), myeloma, and arthritis. 
  • There are 3 major skin changes that occur with PG: ulcerations, blisters and pustules. Doctors speak of 4 different types of PG:  
    • Ulcerative: presents as a painful open sore (ulcer)with a red, irregular border often with pustules
    • Pustular: presents as discrete small, raised, pus-filled spots (pustules) with surrounding redness.
    • Bullous: rapidly forming small fluid filled blisters, known as vesicles, that come together into a larger blister know as a bullae
    • Vegetative: superficial ulcerations filled with granulation tissue (made up of connective tissue and blood vessels) and usually without pus.