Systemic polyarteritis nodosa mimicking pyoderma gangrenosum in a rare association with small lymphocytic leukaemia/chronic lymphocytic leukaemia.

A 48-year-old patient presented with a nonhealing leg ulcer and a raised white blood cell count. He was diagnosed with pyoderma gangrenosum (PG) and small lymphocytic leukaemia/chronic lymphocytic leukaemia (SLL/CLL). Eight months later, after undergoing treatment with chlorambucil for the SLL/CLL, and prednisone, ciclosporin and intravenous immunoglobulin for the PG, the patient developed livedo reticularis and palpable purpura, and was diagnosed with systemic polyarteritis nodosa (PAN). The case highlights the difficulty in establishing a diagnosis of PAN by biopsy of cutaneous ulcers alone, and that a diagnosis of PG should raise suspicion of another aetiology.