Leg ulcerations can occur in systemic lupus erythematosus (SLE) patients with antiphospholipid (aPL) antibodies and/or vasculitis, and it has been suggested that aPL antibodies may play a pathogenetic role in skin manifestations of SLE. To our knowledge, there is only one report of an aPL antibody-negative patient who developed pyoderma gangrenosum (PG) several years before the diagnosis of SLE. We describe a case of a young male affected by SLE who developed leg ulcers diagnosed as PG in the absence of aPL antibodies, where the onset of PG was associated with reactivation of SLE. Effective treatment led to significant improvement in skin lesions and SLE activity.