Pyoderma gangrenosum (PG) is an infrequent neutrophilic dermatosis, which commonly presents with a limited number of ulcerative, pustular, bullous or vegetative lesions associated with an underlying systemic disorder. We report a 34-year-old man with ulcerative PG that was exceptionally widespread and not associated with any other condition. Moreover, it was resistant to steroid treatment and, after prolonged use of ciclosporin, it unexpectedly developed a vegetative pattern, further supporting the hypothesis that the different forms of PG are part of a single clinical spectrum. Finally, dramatic improvement of the condition occurred after treatment with infliximab, an antitumour necrosis factor-alpha monoclonal antibody; however, this produced circulating autoantibodies. Although this has not had any clinical consequence to date, accurate follow-up in patients treated with infliximab is essential to monitor the onset of a possible autoimmune disorder induced by the drug.