Erythema nodosum progressing to pyoderma gangrenosum as a complication of Crohn's disease

Erythema nodosum occurs more frequently than pyoderma gangrenosum in Crohn's disease. We report the occurrence of both lesions in a woman with Crohn's disease and the transformation of one to the other. Pyoderma gangrenosum has been described at the site of previous trauma in Crohn's disease and at the site of other skin conditions in other circumstances, but, to the best of our knowledge, actual progression from erythema nodosum to pyoderma gangrenosum has been reported on only one previous occasion in Crohn's disease.