Pyoderma gangrenosum

• Pyoderma gangrenosum:

  • Presents as a rapidly enlarging, very painful ulcer
  • Part of a group of autoinflammatory disorders known as neutrophilic dermatoses
  • Characterised by a full thickness ulcer with blue/purple undermined borders and pathergy
  • Pathergy = development or flare of skin lesions after minor trauma
• Frequently associated with an internal disease or condition:

  • IBD - more commonly ulcerative colitis
  • RA
  • Leukaemia
  • Chronic active hepatitis
  • Granulomatosis with polyangiitis
  • Behcet disease
• Clinical features:

  • Usually starts quite suddenly, often at the site of a minor injury
  • May start as small pustule, red bump, or blood-blister, often mistaken for a insect bite
  • Skin then breaks down resulting in an ulcer - can deepen and widen rapidly
  • Characteristically the edge of the ulcer is purple and undermined
  • Usually very painful
  • Several ulcers may develop at the same time
  • Deep ulcers heal with scarring
• Diagnosis:

  • Diagnosed by its characteristic appearance and severe pain
  • Pathergy test usually positive - skin prick test causing a papule, pustule or ulcer
  • Wound should be swabbed for microorganisms - but these are not the cause of pyoderma gangrenosum