Pyoderma gangrenosum (PG) is a noninfectious neutrophilic dermatosis of the skin of unknown origin. Skin lesions may be one or several and are often chronic and recurrent. PG is associated with many other diseases including inflammatory bowel disease, systemic autoimmune diseases, and lymphoproliferative disorders.
Clinically, lesions most commonly occur on the legs but may be found anywhere. It usually starts with sterile pustules which rapidly progress to painful ulcers of variable depth and size. The rim of the lesion has a ragged, undermined, violaceous gunmetal colored border. The pathology of early lesions show perivascular mixed neutrophilic and lymphocytic infiltrates with surroundnig edema. Fully developed lesions consist of necrosis and a dense neutrophilic infiltrate with both lymphocytes and macrophages surrounding and involving blood vessels. Ulceration and necrosis follow, with infarcation and abscess formation sometimes resulting. Sk...