We report a 38-year-old housewife with systemic Langerhans cell histiocytosis (LCH) presenting as a chronic vulvar and peri-anal ulcer. She had systemic involvement in the form of diabetes insipidus and bone "hot-spots". She responded favorably to etoposide, 6-mercaptopurine, and systemic steroids, and has been in remission since 10 years. Chronic vulvar ulcers not responding to routine therapy should not be neglected and need to be biopsied repeatedly to come to a specific diagnosis. The vulvar ulcer in our case provided a vital clue to a systemic LCH, with a successful outcome.