The evolution of pyoderma gangrenosum. A clinicopathologic correlation.

Pyoderma gangrenosum is a well-known clinical cutaneous condition, that has had a variety of conflicting microscopic descriptions. In an attempt to further our understanding of this condition, we obtained nine skin biopsy specimens of evolving, fully developed, regressing, and resolved lesions from six patients with pyoderma gangrenosum. We found that histopathologically, pyoderma gangrenosum evolves from folliculitis and abscess formation; it may also show leukocytoclastic vasculitis. The lesions then evolve to suppurative granulomatous dermatitis and finally regress with prominent fibroplasia. We illustrate the clinical and microscopic features herein and compare them to previous descriptions.