Giant cells in pyoderma gangrenosum.

It has been claimed that pyoderma gangrenosum (PG) lesions may contain granulomatous foci when associated with Crohn's disease. To test this assertion, we obtained clinical histories and archived cutaneous biopsies from 34 PG patients. Thirteen of these patients had inflammatory bowel disease (IBD). Immunostaining with PGM1, a macrophage marker, revealed well-formed giant cells with three or more nuclei in biopsies from 6 of 13 patients with IBD. Five of the 6 biopsies came from patients with Crohn's disease and one from a patient with ulcerative colitis. Two were peristomal. In the 21 patients who had PG without IBD, no giant cells were seen. Thus, PGM1+ histiocytic giant cells within a PG lesion may be indicative of associated IBD (p = 0.006), particularly Crohn's disease.