Deposits of complement and immunoglobulins in vessel walls in pyoderma gangrenosum

Previous immunofluorescence studies on pyoderma gangrenosum (PG) proved negative. Biopsies from the ulcer edge of 8 patients with PG were examined by immunofluorescence microscopy. Deposits of complement C3 were seen in the vessel walls of all samples, IgM in three and IgA in one. Granular deposits of C3 were seen at the dermal--epidermal junction in 2 patients. Biopsies from clinically normal skin of 6 of the patients were negative. It is suggested that deposition of immune complexes in the dermal vessel walls may play a role in the pathogenesis of PG.