Pyoderma gangrenosum (PG) commonly occurs in association with various haematological and inflammatory disorders. We report a new association, a Janus kinase (JAK)2 mutation, in a 63-year-old patient with PG. We hypothesise that PG occurs by direct activation of JAK along with signal transducers and activators of transcription (STAT), a common mechanism involved in the pathogenesis of inflammatory and haematological diseases.