Pyoderma gangrenosum in an allogeneic bone marrow transplant recipient

We present the case of a 15-year-old boy who developed facial pyoderma gangrenosum following an allogeneic bone marrow transplantation for the treatment of a 'blast' crisis developing in the course of chronic myelogenous leukaemia. The lesion appeared 7 months before any evidence of relapse. The discussion is focused on both the presentation of pyoderma gangrenosum associated with myelo-proliferative disorders and its pathogenesis via the underlying immunosuppression.