Pyoderma gangrenosum occurring in a lower limb fasciocutaneous flap--a lesson to learn.

Pyoderma gangrenosum is a destructive cutaneous disease characterised by progressive painful ulceration. The occurrence of pyoderma gangrenosum at a surgical site is rare (especially if there is no predisposing illness), but is well recognised. We present a case of a 63-year-old man who developed erythematous ulcerative lesions due to pyoderma gangrenosum in and around a lower limb fasciocutaneous flap used to cover an exposed total knee prosthesis. The lesions were initially confused with postoperative wound infection. No predisposing disorder, other than the rarely reported association with osteoarthritis, was found. The diagnosis is important because its rapid detection not only avoids unnecessary treatment but also allows for prompt intervention with oral steroids. This case is presented to alert surgeons to the presence of pyoderma gangrenosum and its diagnostic confusion with postoperative wound infection.