Pyoderma gangrenosum

Pyoderma gangrenosum, abbreviated PG, is a benign inflammatory skin disorder associated with inflammatory bowel disease.

General

• May be seen in IBD (ulcerative colitis and Crohn's disease) - approximately 30% of cases.

Clinical

• Pathergy = minor trauma (to the skin) results in a non-healing lesion.

Gross

• Skin ulceration - classically on the legs.

Microscopic

Features:

• Early: lymphocytes cells only in the dermis - often perivascular & vascular.
  • +/-Fibrinoid necrosis of vessels at edge of lesion.
• Late: abscess formation (neutrophils).

DDx:

• Vasculitis.
• Sweet syndrome.

Image

• Pyoderma gangrenosum (nih.gov).

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A. Skin, Left Leg from Central Wound, Punch Biopsy:
- Necrotic debris with underlying granulation tissue and benign connective tissue
  with superficial vasculitis, see comment.
- NEGATIVE for skin surface.

B. Skin, Left Leg from Wound and Normal Skin Junction, Punch Biopsy:
- Skin with ulceration, necrotic debris, and superficial vasculitis, see comment.
- Fat necrosis and severe atherosclerosis.

Comment:
The findings are in keeping with pyoderma gangrenosum; however, atherosclerotic disease 
and vasculitis should be considered clinically.  

The vasculitis is seen superficially and is likely secondary to the ulceration.

Alternate

Skin, Left Lower Leg, Punch Biopsy:
- Skin with ulceration, necrotic debris, superficial vasculitis, 
  subepidermal fibrosis and maturing granulation tissue, see comment.
- NEGATIVE for evidence of malignancy.

Comment: 
The findings are in keeping with pyoderma gangrenosum; however, vasculitis and 
atherosclerosis should be considered clinically. 

The vasculitis is seen superficially and is favoured to be secondary to 
the ulceration.

See also

• Inflammatory skin disorders.